Added info...

https://www.pbs.org/wgbh/nova/video/oceangate-tita...

-----*****-----
So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik

I found this about the surface treatment of titanium prior to epoxy bonding in relation to hydration.

https://link.springer.com/article/10.1007/BF005522...

I saw no such treatment of the titanium surface in that earlier posted advertising video.

One question to ponder;
Did the recovery crews partially dismantle the parts for easier/safer handling?
We saw a lifting sling through the porthole and suspected that the window had failed.
Then we saw what looked like one of the titanium rings, that appeared to be separate from the end bell.
So, was the failure so violent as to rip an end ring free from the titanium hemisphere or did the recovery crew remove the bolts while onboard the recovery vessel to make subsequent handling safer and easier?
If the recovery crew did not remove the bolts, the implication is that both the glue joint and the bolts failed simultaneously, leaving the ring orphaned.
While possible, there is really no force on the ring itself that would lead to failure, and once the bolts failed that would relieve any force on the glue joints and if the glue failed first, that would relieve any force on the bolts.

The profile of the sound waves piked up by the navy may shed some light on the failure progression.
For a hull failure, the wave form may be a single burst or peak, possibly followed some time later by sounds of the pieces landing on the bottom of the sea.
For a hull failure followed by a water hammer failure I suspect a first burst of sound as the window fails and milliseconds later a greater sound burst as the end hemisphere fails.
Again possible faint sounds of pieces hitting the bottom.
When it comes to determining the failure progression for the information available to us, we are in uncharted water. (grin)

--------------------
Ohm's law
Not just a good idea;
It's the LAW!

My question from the first thread, anybody got opinions?

I haven't seen anything on how these pieces are brought to the surface. ROV's? Lift bags? Crane with 2 1/2 miles of wire?

I don't see any real disassembly at 12,500 ft.

The problem with sloppy work is that the supply FAR EXCEEDS the demand

You need some extremely high pressure air to make a lift bag work.
It still may be the best way.
Possible, bag to the surface and then retrieve with the rig used to launch the submersible.
Once out of the water on the retrieval platform, disassembly before further handling.

--------------------
Ohm's law
Not just a good idea;
It's the LAW!

Air at sufficient pressure is doable - the challenge is going to be getting sufficient volume.

I'd consider a lifting bag full of petrol sent to the bottom over a disposable ballast with a drogue to control the ascent rate.

A.

Violent is an understatement. There's not much that can withstand a 600mph water jet and especially what follows it.

--Einstein gave the same test to students every year. When asked why he would do something like that, "Because the answers had changed."

Quote (I don't see any real disassembly at 12,500 ft.)

self-disassembly?

Quote (You need some extremely high pressure air to make a lift bag work.)

Just overcome the water pressure, would there be any increase if the fabric stresses due to the high pressure, or just the (inflation - water) pressure? Are there some other issues that have to be addressed?

-----*****-----
So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik

Quote (waross)

If the recovery crew did not remove the bolts, the implication is that both the glue joint and the bolts failed simultaneously, leaving the ring orphaned.
While possible, there is really no force on the ring itself that would lead to failure,

This was a catastrophic implosion at 3600m deep. The shock could easily have blasted the end caps off in a violent manner, separating the ring in the process. Likewise the window.

Much speculation, not much to go on. Looking forward to "Tourist Submersible... Part 18" :)

The problem with sloppy work is that the supply FAR EXCEEDS the demand

As requested, posted from old thread.

Regards

Blakmax

Ok

I had my money on the apalling Tsai-Hill or Tsai-Wu failure criteria giving a totally incorrect prediction of compression-compression strength. I reserve that opinion, but now based on Tugboat's pictures and Rodface and IRstuff postings above, I would add real concerns about adhesive bonding issues. In Tugboat's image, I do not see any significant fore-aft overlap for the adhesive bond. Surely they did not rely on the bond between the vertical face of the five inch composite and the titanium end cap to conduct load. Even people of very restricted engineering knowledge understand that the first rule of bonded joint design is that you NEVER rely on bonds that even have a minor risk of tension loading.

My next concern is the overlap length shown schematically in Rodface's posting between the end fitting and the composite shell. Does anyone have dimensions? One of the most significant stupidities in adhesive bond design is to use the lap-shear strength as determined by tests such as ASTM D1002 to design the overlap length for bonded joints. Further, the strength of adhesives changes dramatically with temperature, so I just hope they provided test data at the low temperatures at depth. Typically, at low temperatures the adhesive is very stiff and the strength is higher, but the elastic modulus is also very high which results in a very low strain to failure.

My next concern is in relation to the surface preparation procedures for the titanium end caps and also for the former shown by IRStuff. Please understand that adhesive bonding is a chemical process that relies on the formation of chemical bonds between the adhesive and the surface of the metal or composite resin. Surface rough ness is a secondary issue. Now, everyone knows that the surface must e clean, so that surface contaminants do not interfere with the chemical reaction. But a clean surface is not a sufficient condition. The surface must also be chemically reactive so that chemical bonds are actually able able to form. Such a treatment will provide a strong bond in the short term.

However, there is a third requirement that many people overlook. Many metals have an affinity for the development of hydrated oxides, for example aluminium (Ok, for the US readers aluminum) will form Al2O3 as soon as the surface is exposed. Over time this surface has a tendency to hydrate to form Al2O3.2H2O. For this reaction to happen, any adhesive bond to the original oxide layer must dissociate so that the hydration reaction can occur. This is the cause of interfacial adhesion failure of the bond. Hydration is exacerbated by immersion in water and the addition of salt. There are essentially three adhesive failure modes:1 cohesion, where the adhesive fractures leaving a layer of adhesive on both surfaces. This is a high strength mode of failure. 2. Adhesion failure where the adhesive separates from a substrate at the interface due to hydration. This is a very weak mode of failure. 3. A mixed-mode failure which is a variable mixture of cohesion and adhesion. This mode occurs as interfacial hydration is happening, with the strength degrading as hydration progresses. I am concerned with the degree of adhesion failure shown in the picture shown by Tugboat.

An essential requirement for longer term bond durability is a treatment applied to the surface to demonstrate that any surface preparation provides adequate resistance to interfacial hydration. The best test for this is the wedge test such as ASTM D3762.

So, I have grave concerns about the composite design, the adhesive bond design and the adhesive bond surface preparation processes. I don't think the company could have PAID ME enough to encourage me to take the trip.

Regards

Blakmax

Lifting bags are open bottomed. More like lifting socks.
As they ascend the air expands and vents out the bottom rather than building pressure that would rupture a closed bag.
Commercial compressed gas cylinders top out at a working pressure of about 2500 psig.

Fun with numbers: (neglecting the weight of the compressed air. The weight of the air would only make things worse.)
Displacement of 1920 lbs of water requires a volume of 30 cubic feet.
So a sock of about 3 ft. dia. by 4.25 ft. high.
Now if we use a tank 3 ft.in dia. by 8.5 ft. high pressurized to 12000 psig, once the tank is opened to the sock, the pressure will equalize at 6000 psig in both the tank and the lifting sock.
Let's neglect the bouyancy of the compressed air tank. It will probably be heavy enough to sink.
So we are looking at a special build tank serving at almost 5 time the pressure of commercially available tanks, for a one time lift.

I think that a simple tank filled with a light liquid and using disposable ballast is the way to go.
Naptha weighs 7.42 pounds per Imp gallon compared to sea water at 1.025. at 10.25 pounds per Imp gallon.
Each imperial gallon of naptha will have a bouyancy of 10.25 - 7.42 = 2.83 pounds.
A used (cheap) 5000 gallon storage tank filled with naptha will have a bouyancy of about 5000 lbs.
The challenge is to connect the tank to the object to be lifted in such a way that the tank is not damaged.
A cable halter and vertical orientation will probably do the job.

--------------------
Ohm's law
Not just a good idea;
It's the LAW!

another article...

https://www.youtube.com/watch?v=rie76UsjPZs

-----*****-----
So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik

Info on Tony Nissen, Director of Engineering, from video Dik links above. David Lochridge was hired at the same time.

https://www.marinetechnologynews.com/news/oceangat...

Dismantlement would be a gross violation of what I would assume to have been instructions to the recovery crew, which is to PRESERVE evidence.

Any intentional retrieval or post-retrieval dismantling would be grounds for firing everyone involved. If they did dismantle anything, how would anyone know what actually happened? Did the dismantlers measure the force required to remove the porthole, for example? Did they wind up creating additional damage in prying the porthole off? And wouldn't it be silly, that they couldn't come up with a different way of hoisting the end cap without damaging the evidence?

TTFN (ta ta for now)
I can do absolutely anything. I'm an expert! https://www.youtube.com/watch?v=BKorP55Aqvg
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Presumably, if the porthole was still in place, it would not be the initiator. Even if it was, that condition was changed by the removal of differential pressure during the accident. Any removal would be documented the way that the location and orientation of each part on the sea floor was prior to removal from there.

They were working on a $100-$500k per day recovery effort with equipment not designed with the intent of lifting such items. DailyMail (for what that is worth) claims $6.5M was spent on the effort. Spending more time to make a more sophisticated effort seems unlikely. Those recovery resources are needed elsewhere.

I do expect that everything was separated by the implosion, particularly the port hole, making this point moot.

It's a surprise they managed the task. It will be interesting to find out what they did.

"I haven't seen anything on how these pieces are brought to the surface. ROV's? Lift bags? Crane with 2 1/2 miles of wire?"
The ROV's used to find it were tether-operated, I thought, so presumably, grab a piece and hoist both together>

The recovered debris has been dissembled and cut, when you look closely. Bolts missing, frame pieces cut. Nothing is bent or mangled.
No sign of any carbon fiber hull pieces. Missing is the titanium rear end bell and ring. I'm not sure how heavy that would be, but likely the ROV attaches lifting cables? ROV used Odysseus 6K

I am surprised at how much trouble the Internet armchair analysts have understanding a carbon fiber composite cylinder in hoop compression. Everything out there is the opposite - a pressure vessel, common in MECE textbook, examples, diagrams. No other application is even close to that of a deep sea sub hull. A vacuum tank delta P is 1atm, not 377atm. I can't see CF being suitable for the application at all.

I was concerned when I read that the design of the composite cylinder appears to have been subcontracted to the manufacturer, who then appears to have used an add on FEA program to a well known modelling program for the analysis.

The entire system of cylinder, rings, end caps, porthole etc therefore appears to have been designed as a series of parts, and not as a whole. The risks of these plug and play stress analysers in the wrong hands have been well documented for years.

Does anyone know if the analysis would likely have used thin shell composite elements, whether this is realistic for a thick skin, and whether this would accurately model the transfer of stress through the thick cylinder due to the pressure loading being applied to the outer face only?

Quote (lucky555)

...No other application is even close to that of a deep sea sub hull...

Except maybe the Advanced Unmanned Search System (AUSS) deep sea sub hull?

Quote (AUSS)

...The center section is a cylindrical graphite epoxy pressure hull with titanium hemispherical ends. The hull provides the central structure and all its buoyancy---no syntactic foam is used...

Huh. Sounds kinda familiar.
https://irp.fas.org/program/collect/auss.htm

Edit add: I'm guessing that this is the technical paper that Spencer used as the starting point for their hull design:
https://www.researchgate.net/publication/235179850...

Quote:

...The AUSS Mod 2 pressure-hull assembly, consisting of a wet-wound graphite-fiber epoxy composite cylinder capped with adhesive-bonded titanium coupling rings, and closed off with titanium hemispherical bulkheads...

If that's so, it could be that they didn't account for scaling factors as they sized their barrel up from 31" x 65" to 66" x 98".

Tethered. I guess it's the only way to transmit high quality data. So 2 1/2 (or more) miles of wire after all. My mind boggles :)

The problem with sloppy work is that the supply FAR EXCEEDS the demand

From what I read, with the significant issues of CF construction, there has to be a rigourous quality control program in place. No matter how accurate your analysis is, the QC is far more significant.

-----*****-----
So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik

How does 'one way' CF accommodate the large compression forces from the end hemispheres?

-----*****-----
So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik

Yes, this should have been made from rings that allowed for radial orientation of the strands and not as a cylinder.

The video used above kept mentioning "one-way" carbon-fiber, while other information has said they had longitudinal and hoop in a 1:2 radio, if I remember right.

Since the submersible failed, there is obviously room for criticism of whatever design went on. But I've not seen anything really that indicated how sophisticated that analysis was. So this may have been the "code monkey" approach, or experts in the field, or anything in between, from what I can see.
For a metallic tube with hemispherical ends with internal pressure, the analysis would be fairly simple and straight-forward.
But throwing in bucking/ external pressure, thick-walled, composite, significant temperature changes, fatigue evaluations, joint/glue design, bolted-joint design, plus an acrylic window- each one of those adds another layer of complication, and it'd be easy to get lost at some point if you weren't really on top of it all. And on top of all that, you have the instant-death-if-it-fails aspect.

One thing I've seen mentioned numerous times is the window only being rated for 1300m. That seems to be confused with the window only being adequate for 1300m, which is entirely different. IE, rating the window for deeper may have involved more testing or more analysis, but wouldn't necessarily have changed the window, either.

JStephen, you left out "lack of significant NDE" :)

The problem with sloppy work is that the supply FAR EXCEEDS the demand

Quote (IE, rating the window for deeper may have involved more testing or more analysis, but wouldn't necessarily have changed the window, either.)

It doesn't matter very much... the whole enterprise is an excellent example or 'bad engineering' or 'non-engineering'. It's because of my exposure to 'bad engineering' when I first started that I don't wear an engineer's iron ring.

-----*****-----
So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik

I would give credit to OG if they took a prototype of their submersible to a deep part of the ocean and did like 100 dives to test depth (what ever that is) and preferably took it on last dive to failure. Then the next boat would have some cred.

Not clear at all what type of test protocol was used, we shall see when reports come out.

There were claims that the hull was laid up in both directions, but it may have been replaced with a cylinder laid in only one direction. The craft was repaired. The repair may have involved replacement of the carbon fibre cylinder.

--------------------
Ohm's law
Not just a good idea;
It's the LAW!

https://www.heraldnet.com/news/titanic-in-reach-as...
Monday, March 9, 2020 5:34am

Quote:

EVERETT — A hoped for visit to the Titanic has been years in the making, but OceanGate now wants to reach the world’s most famous sunken ship with some help from NASA.

The Everett-based company is working with the federal space agency to build a submarine that’s strong enough to survive the pressure of those kinds of ocean depths.

OceanGate first planned to study the Titanic in 2018, but its submarine was hit by lightning. The team tried again the next year, but it didn’t work out because of complications.

With the extra time, the company did more testing and realized the vessel wasn’t strong enough for multiple trips to the sunken ship, almost 4,000 meters under the sea, or about 2½ miles.

They needed a stronger material, OceanGate CEO Stockton Rush said.

“We had talked to NASA in the past, and found out they had a need for this advanced technology,” he said. “It’s one of the thickest structures ever made of carbon fiber. They are also looking to go to the moons of Jupiter and Saturn, and that’s likely going to require advanced materials to be able to melt through the ice and explore these watery moons.”

NASA is using the carbon fiber material to build the vessel’s hull, or the outer part of the submarine. Manufacturing is expected to begin in a few weeks at the Marshall Space Flight Center in Huntsville, Alabama.

Later, the submarine will be assembled in Everett. OceanGate’s headquarters are on Craftsman Way, on the waterfront. About 25 people work there.

In a way, OceanGate and NASA are helping each other.

“NASA can only do this kind of contract work where it sees advantages to advancing technology and there isn’t really a commercial alternative,” Rush said. “We will be paying NASA for the work, and NASA will get access to this technology, so we get a pretty good rate and they get a lot of data.”

The submarine, called Titan, is about 5 feet in diameter and roughly 10 feet long, with enough space for five people to fit inside. The design is similar to another OceanGate submarine, called Cyclops 1.

OceanGate plans to visit the Titanic in 2021 from July to mid-August. A typical dive is around 12 hours long.

Along with researchers, anyone interested is invited to come along and may buy tickets to join the expedition. Proceeds fund the missions.

The group would stay on a ship for eight days at a time, above the wreck site in the Atlantic Ocean, nearly 400 miles from Newfoundland, Canada.

Once at the Titanic, researchers expect to take detailed photos, and scan the ship with lasers and high definition sonar.

“One of the questions that needs to be answered is how quickly is the wreck decaying, what’s its current conditions and how quickly is it going to disappear into the sea?” Rush said.

OceanGate also hopes to study the debris field, where personal belongings may be scattered, and marine life. Around 300 different species are unique to the wreckage, Rush said.

The Titanic sank during its maiden voyage, in April 1912. It was making its way between Southampton, England, and New York City. About 1,500 people were killed.

The luxury marine liner was 882 feet long, 92 feet wide, with space for 3,547 passengers.

Because OceanGate only wants to look around, the company doesn’t need permission to visit the site. However, officials know about their plans. Titanic’s location was first discovered by Robert Ballard in 1985, and photos were later taken by remotely operated deep-dive vehicles.

Rush and his team hope to go back every summer to see how the Titanic changes each year, and make that information available to other researchers.

There’s no set time frame to continue the trips, just until “people stop wanting to go,” Rush said.

Stephanie Davey: 425-339-3192; sdavey@heraldnet.com; Twitter: @stephrdavey.

An article from 2022 that names several companies that were involved in building the Titan's second hull (the one involved in the incident)?

https://www.nwyachting.com/titan-of-industry/

All of OceanGate Inc.’s submersibles—there are currently four including Titan—are developed out of the company’s homebase at the Port of Everett, with testing and research dives often taking place in nearby Possession Sound. Local partnerships abound: OceanGate collaborated with NASA on some of the technical aspects of Titan, but they also leaned on the experts at Boeing and the University of Washington Applied Physics Lab during fabrication. Toray in Tacoma produced the carbon fiber composite material for the submersible, Janicki Industries out of Sedro-Wooley did all the machining work, and then the UW stepped up again to help OceanGate test the pressure vessel at their School of Oceanography. “It’s really unique to have all these companies and resources available to us here locally,” says Rush. “It’s been a great community to work with.”

Well first hull? Second hull? It's all quite confusing.

What is certain is that this video shows a very different manufacturing process from the "wet" one shown in more widely-distributed video:

https://www.facebook.com/watch/?extid=NS-UNK-UNK-U...

Quote (@Demented)

That Herald article implies a very high level of collaboration between MSFC and OceanGate. Was it all complete bollocks out of Stockton's mouth? I think NASA has stated that they "consulted" on it, correct?

Edit to add: if this was really all out of a single source and was not verified with NASA, that seems like quite lazy journalism.

From another thread, I just realised that the non-uniform radial compression stress will create shear stresses with the CF matrix. How is CF with shear? Is the longitudinal compression stress created by the end domes uniform or does it vary across the cross section?

-----*****-----
So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik

More questions about manufacture:

1. The composite cylinder was tape-laid onto a metal mandrel. Did the manufacturer undertake regular compaction as the structure was built up? Usually, composites are compacted regularly as the thickness is added. That was trapped air can be extracted, minimising void content.

2. What resin was used and how was it cured? My experience with composites is that thick laminates are susceptible to thermal runaway with a risk of spontaneous combustion. Maybe they used room temperature curing resins, which in itself has inherent dangers.

3. Given the thickness, they would almost certainly have used a zero bleed pre-preg, which also risks high porosity.

Regards

Blakmax

I went back and had a look at the original videos of construction again like this one

https://www.youtube.com/watch?v=WK99kBS1AfE

The lack of connection between the shell and the titanium ring is unreal. Basically less than 50mm insertion of the CF shell into a C shaped end with very thin inner and outer cylinders. I just can't see how this survived any outings, not to mention 7 or 8.

As to the design itself, who knows what they did? I do suspect a bit of undue reliance on computer says Yes...

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

A few atm will easily push the ends on. More to worry about is heating up under the sun while on the surface. Underwater camera housings only have O-rings.


Wall stress: 55,000 psi compression-
Long stress: 29,000 psi compression
Max shear +/-13,000 psi
(neglecting radial stress)

Does not seem excessive. I think it will be a defect issue.

--Einstein gave the same test to students every year. When asked why he would do something like that, "Because the answers had changed."

More technical stuff on CF.

https://www.youtube.com/watch?v=6LcGrLnzYuU

-----*****-----
So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik

Quote (Does not seem excessive.)

They seem high to me considering they are compressive stresses. I have no background in CF technology. The earlier post I just made seems to think there are general problems with the method.

-----*****-----
So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik

Does CF "bruise" n the same way GRP does?

I.e. no surface damage visible, but deeper layers get broken and create weaknesses?

My issue with the end ring / dome connection to the CF pressure dome is where different materials react differently in terms of reaction under the huge loads it experienced and temperature changes, but about 50mm only is contained within a joint. Any damage within that joint or right at the stress concentration point at the end would have been very difficult to see / repair or monitor I believe. The analysis might all be ok, but the devil is in the details of the connection.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

Apparently it can. In addition, it can debond and lose compressive capacity.

-----*****-----
So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik

So apart from being apparently towed behind the vessel on the latest trip I also saw somewhere that it was regularly transported overland from the Atlantic coast to their base in Everett, Washington state.

Plenty of room there for the odd knock or point damage which wouldn't show up.

Didn't realise this is basically a suburb of Seattle - no wonder they did some sort of work with Boeing.

Debonding under compression didn't take long to find things like this https://www.degruyter.com/document/doi/10.1515/sec...

Doesn't look good. basically gradually fails until "it completely disbonds" once you've reached the critical limit.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

AFAIK they did no work with Boeing - at most they bought material that was scrapped from Boeing without informing Boeing of their plans.

Considering that this effort parallels Theranos - the leader wants to break out of the mold, fires or ignores everyone with experience in the field, opting instead to surround themselves with ignorant (not stupid, but uninformed) Yes people it is clear there were steps taken to keep the end use from anyone with relevant knowledge.

The difference is the leader at Theranos was smart enough not to participate in the use of the product. This time it was self-correcting.

^Agree.

Recall this post from Part 1: FacEngrPE (Mechanical)1 Jul 23 19:34

Refers to an article from Design News about successful submersibles made from CF composites.

OG's problem was apparently not so much use of CF composites as such, but rather with design and manufacture of the same. Very different corporate cultures.

The problem with sloppy work is that the supply FAR EXCEEDS the demand

Quote (LittleInch)

Does CF "bruise" n the same way GRP does?

Yes.

It's a common failure mode for composite tanks. There's a safety measure to catch them - in internal delam will result in pressure moving between plies, and will 'blister' the tank wall before failure, so they're easy to catch by visually inspecting the tanks.

For a tank wall in compression, I would expect any delaminations within the wall layup to result in visible blisters inside the tank. In theory you'd be able to catch them via visual inspection, but for the OceanGate design, you would need to disassemble the pressure vessel and pull out their internal tank liner to inspect the tank. I haven't heard conclusively either way but given the general safety culture that was on display in other areas of the business, I have a strong doubt they were doing that after every dive or with any regular frequency really.

Quote (blakmax)

2. What resin was used and how was it cured? My experience with composites is that thick laminates are susceptible to thermal runaway with a risk of spontaneous combustion. Maybe they used room temperature curing resins, which in itself has inherent dangers.

I don't know that we have specific information on the resin, but there was some info about the manufacturing process in the previous thread. They used a very long, low temperature cure. It was 7 days at 125⁰C, or something to that effect.

Quote (waross)

So, was the failure so violent as to rip an end ring free from the titanium hemisphere or did the recovery crew remove the bolts while onboard the recovery vessel to make subsequent handling safer and easier?

I have a hard time seeing any failure mode where the end bells stay on - either the CF hull buckles and the end bells are blown off, or the acrylic window failed and the end bells were blown off. There would have been a huge pressure spike due to water hammer, an order of magnitude beyond the pressure the sub was design for and also of the opposite sign.

For normal thickness material I can see that but when it was what 5 inches / 125mm thick maybe those normal bruises didn't show, plus the internal and external "cladding" would have reduced the visibility of this.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

Quote (LittleInch)

For normal thickness material I can see that but when it was what 5 inches / 125mm thick maybe those normal bruises didn't show, plus the internal and external "cladding" would have reduced the visibility of this.

Certainly possible. As I said I doubt they were pulling out the internal liner to inspect the tank wall, and even if they were - I agree it's possible that the telltale blisters may have been difficult or impossible to detect visually.

I would expect that even at this wall thickness they would be very easy to detect with ultrasound. But again, continuous safety inspections weren't a part of their process as far as we know.

I've read a fair amount about CF testing in compression. Some good stuff linked here..

But what about fatigue response in compression? Seems like a vital bit in this failure.

I could look it up, but I'm being a bit lazy!

I calculated the 29,000 psi compressive load using area of 11ft2, of the 5 inch wall. If it's 50mm thick at the joint, that's going to be about 2.5x higher stress on the face of the joint. 75ksi +/-
I hope the titanium was acting as a retainer ring.

--Einstein gave the same test to students every year. When asked why he would do something like that, "Because the answers had changed."

But what about fatigue response in compression? if there are no delaminations, then fatigue response is typically good in compression. However, if there are delaminations, then they can grow and eventually buckle under compressive loading.

The fatigue point is not something we should dismiss IMO, but I'm not sure if less than 10 full cycles to rated depth really would qualify as a fatigue failure in my mind.. Reads to me like gross overload.

I don't think it's really fatigue, but rather damage to the material on loading.

-----*****-----
So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik

Based on the videos posted, it looks like they also made a rather huge design change between the first and second cylinders, since the first had a rather conventional looking "spool" upon which the CF was laid, but the second one was flangeless, presumably to make it easier to lay the longitudinal plies, but that possibly weakened the connections between the cylinder and the endcap mounts.

TTFN (ta ta for now)
I can do absolutely anything. I'm an expert! https://www.youtube.com/watch?v=BKorP55Aqvg
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The layup has to be done on some kind of mandrel. It either becomes part of the finished cylinder i.e. a thin shell, or the mandrel has to be easily removed from the cured layup. Segmented or something.

An integral mandrel would prevent any sort of inspection of the inside surface of the finished cylinder. It might hinder of any NDE of the same.

The problem with sloppy work is that the supply FAR EXCEEDS the demand

@snTMan

what would be typical material/thickness for a mandrel that is intended for leaving-in-place? A removable mandrel seems very interesting, what is it coated with to prevent sticking, is the removal destructive?

rodface, I can't really say, but maybe a 1/4" thk shell, backed up by a more substantial mandrel of some sort would likely do. One of the layup videos in the Part 1 thread seems to show some bolted end plates, no clue as to further details.

Mold releases are routine, but imagine trying to remove one cylinder in intimate contact with another with no draft, etc. One being a kind of fragile composite. Ir could prove impossible.

The problem with sloppy work is that the supply FAR EXCEEDS the demand

I have no experience with fabrication of a composite structure of this size but a segmented shell would not be difficult to make or use. The zero draft becomes a non-issue. Is a fully cured 5 -inch thick wall carbon-fiber tube really a 'fragile composite' for handling and working with for the conditions of manufacture? I cannot imagine this tube could not have cores removed without issue. At one atmosphere and room temp, the tube is highly capable for any load cases, no?

@SnTMan

Would be fascinating to learn the exact procedures that were carried out, but unfortunately I am sure that the parties involved will do their best to take this information to the grave.

I have been thinking about this disaster a lot; it seems that a promising avenue of submarine engineering development has been chopped off at the knees because of the sloppy work done here. Given enough funding, R&D, experimentation, the carbon fiber submersible could very well be realized. But thanks to this incident, it may be another 50 years before these concepts come to fruition through some means.

It's almost like witnessing a disaster that stalled the onset of powered flight by several decades. Imagine how different the world would be if Kitty Hawk was delayed until the 1940s.

@Brian Malone

The tube certainly seems sturdy; I've wondered how it was handled after manufacture. We've seen the video of them adhering an end cap; but how did they adhere the other end cap and then flip it over?

They were certainly pushing the envelope, but it seems that more funding and effort was needed to really take such a cutting-edge R&D effort to a safe conclusion.

I suppose that, given favorable COEs of the composite and mandrel that following an elevated temp curve, that the mandrel could shrink more than the cylinder, parting the two. Defer to the composites guys here :)

Wouldn't take much damage to the inner surfaces at mold removal to make the cylinder unusable.

Note my earlier post: CF Composite submersibles are possible. Just not by OG :)

The problem with sloppy work is that the supply FAR EXCEEDS the demand

FEA study using Abaqus:

https://youtu.be/i-bvNHCCpFo

Quote (SnTMan)

Mold releases are routine, but imagine trying to remove one cylinder in intimate contact with another with no draft

This part of the operation is solved. Mandrel is coated with mold release, after curing there is very little friction between the part being cast and the mandrel. All sorts of fiberglass and carbon components - think light poles, javelins, oar shafts, arrow shafts, baseball bats, carbon tubes for bicycle frames, pole vault poles, flag poles, etc etc etc are made by filament winding on a release-coated mandrel with no taper. Lots of those things have much thinner walls and are much more fragile than the hull shell would be, and they are easily removed without damage.

Given that the manufacturer of the shell is a reputable manufacturer of filament wound composites, I would not expect this part of the process to be a component of the root cause.

Quote (SwinnyGG)

I have a hard time seeing any failure mode where the end bells stay on

There were titanium rings glued to the ends of the carbon fibre hull.
These rings were bolted to the titanium end bells.
In the picture of one of the rings, there appears to be remnants of the glue and possibly fibre.
I suspect that the recovery crews removed the bolts holding the ring to the end bell.
The ring would have stayed with the end bell, unless the bolts were woefully undersized. I guess that that was possible.

--------------------
Ohm's law
Not just a good idea;
It's the LAW!

On the "FEA study using Abaqus"-
I have wondered out some of that would actually work.
You have tremendous forces applied on the hull, but also, a lot of mass has to move for that water to advance inward.
I assume that is a problem that may be theoretically solvable (ie, assume initial condition as spherical void in infinite compressible water at constant pressure, etc.)
In the case of the Abaqus model, he's probably assuming constant pressure on the outside, so the dynamic effects may be skewed considerably, as it is just the shell that has to be accelerated, rather than the shell plus tons of water.

Quote (JStephen)

a lot of mass has to move for that water to advance inward.

At the pressures you're dealing with at 4,000m of water depth, the masses of the the components involved mean very little.

At 4,000 m, the amount of force on one of the end bells, along the long axis of the sub, is roughly 8500 tons

Quote (JStephen)

In the case of the Abaqus model, he's probably assuming constant pressure on the outside, so the dynamic effects may be skewed considerably, as it is just the shell that has to be accelerated

Yes I agree that model is a bit questionable once things start moving. However either way the implosion would be a split second.

It does look like 3ms is too fast to include water acceleration time.

If we try to include water acceleration (neglecting the mass of CF)
1 ft3 of water under a pressure of 5000 psi (720k/ft2) will accelerate at 358ft/s^2
Taking average velocity over a timestep, the CF shell transverses the roughly 5ft internal radius of the CF tube in still < 0.2s

But anyone inside would still have been totally destroyed in 0.1ms or less.

--Einstein gave the same test to students every year. When asked why he would do something like that, "Because the answers had changed."

SwinnyGG, thanks for the clarification, I am not overly familiar with the processes, and I did not mean to imply damage from de-molding played any part in the failure.

The problem with sloppy work is that the supply FAR EXCEEDS the demand

Quote (SnTMan)

SwinnyGG, thanks for the clarification, I am not overly familiar with the processes, and I did not mean to imply damage from de-molding played any part in the failure.

No worries. It's a niche process, one of those things most people never get exposed to.

Quote (1503-44)

1 ft3 of water under a pressure of 5000 psi (720k/ft2) will accelerate at 358ft/s^2

Respectfully, you have a unit conversion error somewhere, or something. You're off by multiple orders of magnitude

1 m³ H₂O = 1025kg
Water pressure @ 3800m = 39,000 kPa = 39,000,000 N force over 1 m²
f=ma
f/m=a
39,000,000N/1025kg = 38,050 m/s². 125,000 ft/s.

That's 38 meters/s of velocity added per millisecond. At the third millisecond of the event, the water/carbon/playstation controller/formerly human jelly is already traveling at 400+ f/s.

The total time to traverse the diameter of the hull is less than 10 milliseconds.

There's also another effect at play which hasn't been discussed really at all. At these pressures, the density of the water is increased 2.5-3% due to pressure effects. Any water instantaneously exposed to atmospheric pressure is also going to explosively expand, including gaseous cavitation of any dissolved gases present in the water. This effect increases the rate at which the 1 atm bubble inside the sub will close and equalize.

This is not something being bent under moderate pressure. The scenario we are discussing is literally an explosion in reverse. Huge amounts of pressure and energy are involved.

You are right. I divided 720 by 1.98 slugs, not 720kips, lost 000 there so my number should be 720,000 / 1.98 slugs= 358,000 ft/s^2

--Einstein gave the same test to students every year. When asked why he would do something like that, "Because the answers had changed."

Quote (Skinny)

This is not something being bend under moderate pressure. The scenario we are discussing is literally an explosion in reverse.

Yes it would be supremely violent. There is no
cushioning effect as the air gets compressed. No balancing of internal and external pressures as the sub fills up. This is an explosion running backwards.

Look at what happens with underwater explosives; the explosion grows a bubble, which expands until the energy is used up, then the bubble collapses again, only to rebound again.

In the case of the sub you start with a pre-made bubble, but it’s the same in terms of energetic collapse.

I think analyzing what happened in the last few milliseconds (or microseconds) of this crafts life is an interesting, albeit academic exercise. Kinda like analyzing what happens in an airliner when it hits the side of a mountain at 3-4-500mph. Well, it hit the mountain and bad things happened FAST. Got that.

Back to why this thing failed. A few predominate theories:

1. Acrylic view port blew inward. Could have happened. But in that case the water jet may have blown off the aft end bell, but would have expected most of the CF hull to remain at least partially intact, especially fwd.

2. Glue joint between TI end cap and CF hull. Could see that failing or extruding allowing a leak of high pressure SW into the hull. Again, in this instance would expect the hull to at least remain mostly intact.

3. Catastrophic crush failure of the CF hull. This is what I am putting money on. As it seems the end bells and retaining rings were recovered intact with little of the CF remaining attached (just going on photos, holding off solid judgement til solid analysis).

My thinking now is that high pressure exterior water got into the laminate and weakened it. 5-6000psi does some crazy things. My personal thought is osmosis, but I have nothing to base that on but gut feel. Water at that pressure moves through fibers, and once inside the laminate structure can do weird things.

And it all comes back to an apparent lack of a serious design review and test protocol.

Should have dove the thing 100 times to design depth, last dive to failure depth to confirm analysis. Seems that was not done, or anything like it.

Quote (MechinNC)

Should have dove the thing 100 times to design depth, last dive to failure depth to confirm analysis.

100%.

There's been a lot of talk over the absence of "non destructive" testing. However you'd think a destructive test would be more compelling?. Composite Energy Technologies claims: "We’ve built vessels that we’ve cycled 200 times (to deep-sea pressures) and then brought to implosion and those fail at the same depth as new ones"

What about that James Cameron DeepSea Challenger, and the Steve Fossett sumbersible? Did they test those to failure?

I imagine the Mariana Trench littered with CF submersibles taken to crush depth if deep sea tourism ever takes off.

CET PROVED their designs and would not put people in them.

OG BELIEVED in their designs, and did.

The problem with sloppy work is that the supply FAR EXCEEDS the demand

Quote (MechinNC)

1. Acrylic view port blew inward. Could have happened. But in that case the water jet may have blown off the aft end bell, but would have expected most of the CF hull to remain at least partially intact, especially fwd.

2. Glue joint between TI end cap and CF hull. Could see that failing or extruding allowing a leak of high pressure SW into the hull. Again, in this instance would expect the hull to at least remain mostly intact.

Either of these types of failures still result in catastrophic destruction of the hull. At pressures this great, with an effectively infinite supply of energy feeding whatever happens, typical intuitive thinking does not apply.

There is no scenario where a leak starts trickling water in somewhere and the sub takes 30 seconds to fill with water.

High pressure entry of water through the pressure vessel wall, at any point, results in a relatively large mass of water impacting something at very high speed and detaching it from everything else. What follows that is a series of extremely fast oscillations in pressure with huge spikes, as the air 'bubble' which was previously inside the hull collapses, in turn creating a series of very, very powerful shock waves in the water. It is literally exactly the same as what happens when a depth charge detonates underwater- the explosive generates a gas bubble, which then collapses at extremely high speeds. The shock waves from that collapse cause as much damage, and potentially more, than the original detonation did.

This is why the SOSUS system was able to record this event - it would've been nearly as loud as the detonation of an actual depth charge.

Quote (Well, it hit the mountain and bad things happened FAST. Got that.)

Reminds me of the last thing that goes through a bug's mind when it hits your windscreen...

-----*****-----
So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik

Huh, I only just noticed that there were actually two rings recovered, so were there only two ever, or were there four as implied in the FEA video?

TTFN (ta ta for now)
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I think there were only two, attached to the CF cylinder and the titanium end caps bolted to them.

-----*****-----
So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik

I agree there are likely only two rings (one at each end). See this pic:



The FEA guy may have made a mistake with the ring geometry. Look at the ring vs the FEA model. The ring proportions seem different in the FEA, as though the FEA ring is twice as long as the real one? Dunno.. it's weird

Spinney, there is still a difference between our calculations. My velocity is now 3.28 x yours.
I was thinking that it would be an energy/unit mass equality, but it is equal only as far as pressure on a ft2 or a m2. When pressure is equivalent per unit area, Volume, and hence the mass of water we accelerate, differs by a factor of 3.28. We have to decide on a finite mass of water to accelerate. Not sure how we should do that exactly, but it cannot be more than the wedge segment of the tubes cross sectional area described by the radii of the unit area to the tubes central axis. 1 ft3 implies a layer of water 1ft thick wedge moves from the outer shell to the center. 1m3 implies a 1m thick wedge. As the radaii is only 1.5 something, a 1m3 volume appears to be too large. I think we have to do the simulation accelerating many thin layers of water each moving towards the tube axis. That's beyond my pay grade, so I could just agree that it is somewhere inbetween 1/1000 of my original 200ms and whatever your time is, Or we both could just say ... about as instantaneous as you can get. In which case the FEA model may have accounted for water mass accelerations.

--Einstein gave the same test to students every year. When asked why he would do something like that, "Because the answers had changed."

In regards to the plastic view port, was this one piece, or two sandwiched together in a mirror orientation? I have seen photos, and a removed video, of the craft having a flat face view port held on by 4 fasteners with no bolted ring. Unsure if that was just a testing or transport piece as it appears to be their original titan retrofit with stuff from Cyclops 1 from some 2021 testing.


Also, did some more digging around in their press releases but don't have the article handy.
With covid-19 restrictions, NASA was shut down and not manufacturing their pressure chamber. OG employed a hazmat team to enter MSFC to retrieve their materials, which were then brought to private contractors and the new pressure vessel built. The earlier article I posted appears to be some jumping the gun press release from OG.

Quote (1503-44)

difference between our calculations. My velocity is now 3.28 x yours

Yep. 3.28 feet in a meter.

My intent was just to put a number on the collapse at the order of magnitude level. This is a weird calculation to try to make, in that the pressure is the same everywhere (or, at least, the difference in pressure over 1 meter is negligible for our purposes) which means as you make your assumed volume to accelerate smaller, pressure does not change, so acceleration rises rapidly to compensate.

The real value is hard to know without much more detailed math, which neither of us are going to do (at least, I'm not... juice not worth the squeeze, etc). I do think that a thinner layer makes more sense - if I had a gun to my head, I'd bet your updated number may very well be closer to reality than mine.

But ultimately, I think if we're talking within the same order of magnitude (which we now are), we're close enough for our purposes.

I'm having trouble accepting the acceleration of a volume of water, such as 1 cubic foot or other volume.
When that cubic foot accelerates, it doesn't leave behind a vacuum.
An expanding cone of water behind the subject cubic foot also accelerates, at a reduced rate, depending on the distance from the breach.
The expanding gas bubble may also be misleading.
As the bubble of air in the hull is compressed to 400 atmospheres, it will be at equilibrium at about 1/400 or 0.25% of the original volume.
If inertia takes that down to a smaller volume, the rebound volume will still probably be less than 1% of the original volume.
The bubble from an explosion will be many times the volume of the hull, and will be at a pressure above the pressure of the surrounding water.
The ratio between the bubble volume of even a small explosion compared to the bubble volume the implosion will be some multiple of 400:1.
I suspect a progressive failure and collapse of the hull in such a way as to tear the composite away from the end rings.
I suspect that the recovered titanium parts may have been brought the last few feet to the surface on the launch platform, and that the ring bolts and possibly the viewport bolts were removed there in order to make a safe lift onto the deck of the recovery vessel.
I am waiting to see, and I won't argue this suggestion strongly.

--------------------
Ohm's law
Not just a good idea;
It's the LAW!

I thought the FEA model looked a little off.

If there were only two rings, then it's interesting that neither ring was found connected to its corresponding end cap, although, from the photos, the bolts holding them together weren't particularly large.

As for the implosion timeframe, I'd go with the single digits milliseconds after the hull was breached. If we consider one inch area (5 inch deep) of CF accelerated by the hull pressure, we get


So, it takes only about 18 ms to accelerate to the speed of sound in water at that depth, and only about 3 ms to even reach the center of the hull, ignoring any resistance the hull might have provided and the water density changing. 3.5 ms is long enough for the water to fill in behind the CF chunks. We could argue that this might drop the apparent pressure, but halving the pressure only changes the number to 4.3 ms, so whatever exactly happened, it occurred within a few milliseconds.

TTFN (ta ta for now)
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The layer of water behind the initial layer has exactly as much pressure forcing it inward as did/ does the initial layer, but now no liquid in front of it "holds it back". Its following the first layer in with the same acceleration as the first and just as quickly as the first, a chain of railroad cars linked together, no springs in the couplings. The second layer immediately follows the first. Any air is immediately adsorbed into the water at that pressure. All that would probably happen faster than a pressure wave can be transmitted in water, and like a black hole, no energy could escape, so all goes in the one direction towards the center. Above critical velocity, waves do not travel upstream. At impact, only then is it nearly all reflected outward, a void (of water vapor at its vapor pressure) is probably created again, and I'm neglecting any temperature changes, a HUGE error, as we will see). The size of the void continues to expand, until the power flux decreases with the expanding surface area of the spherical pressure wave until further outwad expansion cannot be sustained, overcome by wthe cumulative effect of water's high bulk modulus, which reverses the action to implode once again. Like the pulsed diagram of the process of an atomic bomb shown somewhere up above, each wave reducing in power until it finally is dissipated. Cavitation is much the same process, which is why it can be so destructive. There are actually some shrimp that kill their prey by snapping their claws so fast that the resulting shock wave from cavitation that was created kills or disables their immenent meal.
The Pistol shrimp, temperatures as high as the surface of the sun
https://m.youtube.com/watch?v=eXR--I99S60
https://m.youtube.com/watch?v=jW-DLxze1IA

--Einstein gave the same test to students every year. When asked why he would do something like that, "Because the answers had changed."

The bolts holding this thing together for both the end cap and the viewport were only there to stop the end caps and view port from falling off when this thing was on the vessel and to stop water getting in from wave action / right on the surface.

As soon as this thing descended more than 5-10m, the external force from the sea became the sealing force.

When you look at the size of the components and the size of the bolts they would be unable to hold more than about 1 bar internal pressure IMHO or maybe 10 at the very most. The extraordinary violent implosion would have sheared them all virtually instantly.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

Quote (waross)

When that cubic foot accelerates, it doesn't leave behind a vacuum.
An expanding cone of water behind the subject cubic foot also accelerates, at a reduced rate, depending on the distance from the breach.

Correct - but at the depth we're talking about, the amount of energy available to feed the collapse - basically 100% of the potential energy of the water column above the sub - is hundreds or thousands of times larger than the amount of energy it takes to accelerate the volume of water required to close the bubble. In simplest terms, you're talking about a reservoir of potential energy 3800m tall, which only 'falls' 1.5-2m. There's a large amount of energy consumed in the collapse, but that large amount of energy is still a tiny percentage of the energy available.

Point is, yes- there's energy required to 'backfill' the volume of the collapsing hull - but the energy required is coming from an infinite reservoir.

Quote (waross)

The bubble from an explosion will be many times the volume of the hull, and will be at a pressure above the pressure of the surrounding water.

It would be at standard temperature and pressure. But we aren't talking about standard temperature and pressure - we're talking about a 6000 psi environment.

When an explosion happens underwater, the explosive becomes a cloud of gas, rapidly expanding. At some point, assuming the explosion is deep enough to not breach the surface, the expanding gas bubble reaches a point where the gas pressure and surrounding water pressure are equalized, at which point the gas bubble stops expanding and the water causes it to collapse. When the bubble collapses, effectively all that water slams together at the center point of the explosion, creating an extremely powerful shock wave.

This collapse would have involved the same interaction - surrounding water accelerating to fill the void at extremely high speed. Imagine a scenario where instead of imploding, we stopped time and just waved our magic wand and caused the sub to cease to exist, leaving behind a Cyclops II shaped hole in the water, filled with air, at 3800m. If that bubble of air was preserved and allowed to float to the surface, its volume would expand by your 400x multiplier.

If you make the analogy to an explosion, the upper limit of the energy involved in the collapse of the sub is exactly the same as the explosive energy it would take to create a gas bubble of the exact same volume as the sub, at 6000 psi ambient pressure.

Alternatively, the energy involved in the explosion would be the amount of explosive energy required to create a gas bubble 400 times the volume of the pressure hull at standard pressure.

We can actually calc this out. On average, TNT produces roughly 1 liter of gas at standard pressure, per gram. The approximate volume of the hull of the sub is/was 8.1m³

8.1m³ = 8100L
8100L gas = 8100g TNT at standard pressure, or 8.1kg of TNT.

If you assume 400 bar pressure environment for the 'explosion', to create a gas bubble of 8.1m³ volume, you would need 3,240kg of TNT.

That's not a nuclear level of explosive energy.. but 3 tons of TNT is a LOT of energy.

I suspect strongly, the air within the container was simply displaced.

-----*****-----
So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik

As was everything else :)

The problem with sloppy work is that the supply FAR EXCEEDS the demand

It disappears as it is absorbed by water at high pressure, like CO2 bubbles in a Coca-Cola bottle, most is in solution until the pressure is released. If that block of water makes it to the surface, it will degass.

--Einstein gave the same test to students every year. When asked why he would do something like that, "Because the answers had changed."

Yep. That 8 m³ of O₂ was transported down to the bottom of the ocean, never to return to the surface.

That's another component that would add destructive energy. The water at the very front of the pressure wave resulting from failure of the hull would not only be moving extremely quickly - it would also rapidly lose any gasses in suspension.

Probably only a small percentage of the total energy. I also don't know the typical quantity of gas in suspension for water that deep. There must be some, since stuff does live down there.

Quote (waross)

When that cubic foot accelerates, it doesn't leave behind a vacuum.

It will if it has to. Look at the Hydraulic Press video mini test implosion, where are large vacuum bubble appears outside of the hull, due to the water going into the hull. This was at 80 bars.




The implosion was far more violent than you're imagining it.

That's the cavitation void.

On an aside note, GPT CHAT WARNING
maybe this deserves a thread all on its own. Yes. I will do that.
Basic physics question.

https://chat.openai.com/share/5dcbc4ac-9c36-45e4-9...

--Einstein gave the same test to students every year. When asked why he would do something like that, "Because the answers had changed."

The conditions inside the limited volume of a test chamber are far different from the vast volume of the ocean.

Yes it's different. It's confined. I was making the point that water will form a vacuum (cavitate) next to an imploding hull if it needs to.

Does this sound correct:
based on 8.1 m^3,
about 286 cubic feet.
@ 64 lbs per cu ft, = 18,590 lbs.
18,590 lbs x 12,000 ft depth = 223,080,000 ft lbs of energy in the collapse.
Ouch.

--------------------
Ohm's law
Not just a good idea;
It's the LAW!

If its Lbs-force then Lbs-force x distance is a unit of potential energy.
Power is energy/unit time. i.e. ft-lbf/s i.e. 1 Horsepower = 550 ft-lbf/s

Well, that is what makes the hydro turbines go round and round.

-Einstein gave the same test to students every year. When asked why he would do something like that, "Because the answers had changed."

Quote (waross)

18,590 lbs x 12,000 ft depth = 223,080,000 ft lbs of energy in the collapse.

It's close. The volume is slightly less though. I have 6.2m3.

So the energy in SI is 3600m * 6.2m3 * 1000kg * 9.8 = 218736000 J (161333530 ft lbs)

1 gram of TNT is 4184 J, i.e. the energy is 218736000/4184 = 52279 gram of TNT. That's a figure being bandied about in the first thread. 50kg of TNT

Quote (IRStuff)

Even if you fixed the units, you're calculating gravitational potential energy, which is not relevant for this problem

The energy is the gravitational potential of the volume of displaced water

I know it's semi semantic and I'm being a pain in the ass but.. The hull was 2.54m long from flange to flange, 1.68m diameter, with hemispherical ends.

V_H = πr²L + (4πr³)/3
V_H = 3.14159 * 0.84² * 2.54 + (4*3.14159*0.84³)/3
V_H = 5.6 + 2.5 = 8.1m³

It makes a roughly 30% difference in the amount of energy we're talking about. Which is a lot.

Quote (SwinnyGg)

The hull was 2.54m long from flange to flange, 1.68m diameter, with hemispherical ends.

Yes. But that’s the outer dimensions. It’s the inner dimension available for implosion.

The outer dimensions are the amount of displaced water, which is what defines the energy available. If the pressure hull was filled with solid steel, it would be unable to implode but would have the same submerged displacement. You'd really need to know the exact volume of the entire, fully assembled sub to get a close number - but since a lot of the structures outside the hull are not pressure tight it's hard to know what the true submerged displacement is.

Quote:

The outer dimensions are the amount of displaced water, which is what defines the energy available.

True, but the noncompressible parts don't give up their energy, so all the titanium and 5 inches of CF displace water, but the water can't fill that back in when the structure collapses. Only the compressible volume can give back the potential energy.

TTFN (ta ta for now)
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I do not believe that the energy released in the implosion can come from the gravitational potential energy of the 3600m high column of water above the vessel.  The implosion is said to have happened in about 20 milliseconds.  The velocity of sound in seawater at the low temperature we are talking about is ~1400m/sec, so the column of water involved can be no more than about 30 metres high.

As I said in my posts in the first thread on this catastrophe, I believe the implosion's energy comes from the strain energy released when the water in the vessel's immediate vicinity is suddenly decompressed.

 _{—————————————————————————————————}
^{Engineering mathematician / analyst.  See my profile for more details.}

Denial it’s the same thing. All that intense pressure and strain is the gravitational energy of the water above. Calculating the gravitational potential is simply a way of neatly quantifying it rather than all the nonsense of calculating strained columns of water.

Correct. The strain energy stored in the Hull, the energy stored in the compressed water, everything, was all put there by the weight of the water column above. Its far easier to that one calculation.

The velocity of sound is the velocity of the pressure wave in static water. We are not counting on any pressure wave to move through the water to distribute pressure to adjacent water particles. All of the energy is in the exact spot it needs to be in to be released upon implosion. All the water involved in the implosion was initially pressurised to the full 5200 something psi. No pressure wave traveling at sonic velocity had to be added. The simple removal of the CF shell counteracting the existing 5200 psi, unbalanced the pressure on the adjacent water particles, causing the 5200 psi on those next particles to accelerate into the void left by the shell, accelerating the collapsing shell further inward as well. That happened faster than sonic velocity, thereby no pressure wave traveled outward to even slightly resist the 5200 psi on any adjacent particle, causing them also to accelerate, with their full 5200 psi now unbalanced pressure, inward. No outbound pressure wave is started until water from both sides of the CF tube impact at the centerline, causing velocity to zero. That KE is then converted to pressure wave that can now travel outward, since the imploding water has come to a stop, no inward velocity now allows the pressure wave to begin its outward journey and to start pushing water particles in the opposite direction.

Assuming the CF shell shattered and the titanium ends simply came off the shell intact, nothing was compressed, all of those bits retained their individual original volumes, none of that total material volume ever displaced any water, so none of it was part of the energy released, ie nothing vanished into thin water, so its the inside diameter that defines the space available for energy extraction.

--Einstein gave the same test to students every year. When asked why he would do something like that, "Because the answers had changed."

re health monitoring, there is an ASTM guide for using acoustic emission for SHM: https://www.astm.org/e2983-14r19.html

I am still wondering if they heard any sort of a boom at the surface ship. Maybe it was too faint to get their attention. Clearly the energy traveled to the surface if the navy was able to pick it up. Whether it made it out of the water into the air and still be audible is a different story.

The standard is barely 3 and half pages and is more about the requirements for a SHM is supposed to do as opposed to how to do it.

TTFN (ta ta for now)
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Quote (IRStuff)

the noncompressible parts don't give up their energy

They don't contain any 'energy' - the energy in this equation comes from the displaced water. They contribute to that.

Anyway, we're onto semantics. Not trying to be a pain in the ass. I won't get all worked up about it. Either way its a gigantic reservoir of energy available.

Quote (SwinnyGG)

They don't contain any 'energy' - the energy in this equation comes from the displaced water. They contribute to that.

They entire hull does displace water, that's correct. However only the space within the hull provides implosive energy. The hull material itself does not, because it cannot implode. It's not a matter of semantics.

Quote:

They don't contain any 'energy' - the energy in this equation comes from the displaced water. They contribute to that.

Yes, but if they are incompressible, then no water displacement change takes place, so they do not contribute to the energy of the implosion. It's no different than the external components of the submersible, which displaced water as well, but they obviously contributed nothing to the energy of the implosion.

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Inrushing water can only occupy the space created by changes in volume. Presumably the CF density did not change, the bits and pieces still occupy their total original material volume. The sardine can thickness can be ignored.

--Einstein gave the same test to students every year. When asked why he would do something like that, "Because the answers had changed."

The quantity of water that has been displaced, ie the entire submerged displacement of the sub, has been 'lifted' - it has had its level of potential energy increased.

When the implosion happens, there are three energy sinks which are able to absorb portions of this available potential energy:

1) The gas bubble, which absorbs potential energy from the water column, by rapidly collapsing under high pressure

2) The hard components of the sub, which absorb potential energy as they are bent/broken/shattered/scattered by the implosion

3) The water itself, which absorbs some energy as heat, and whatever energy is absorbed in order to dissolve the gas bubble back into the water (although I'm not 100% sure of the physics on that, maybe it's an energy neutral interaction)

The energy it takes to break all the broken stuff, bend all the bent stuff, and scatter all the stuff that's lost also comes from the water column and is completely separate from the energy consumed to collapse the bubble.

I'd rather not try to calculate that strain energy bit. It requires too much data for one.

--Einstein gave the same test to students every year. When asked why he would do something like that, "Because the answers had changed."

Quote (1503-44)

I'd rather not try to calculate that strain energy bit

I don't intend to try - even if we had all the required information, it would be a complicated thing to try to calculate. And we have very little of the information we would need. But if you wanted to figure out the actual amount of energy absorbed in the implosion to the Joule, you'd need to calculate it.

Some of the available energy is going to go into heating the water that's involved, which would be some small percentage of the total. That would be a very complicated thing to try to compute as well.

Since we can't calculate every component of the whole, the best we can do is establish what the upper limit of absorbed energy is - and that is represented by the potential energy of the total submerged displacement of the entire vehicle at that depth.

The potential energy of the displacement of the air in the hull alone is still a useful number to have for the thought exercise we're all conducting - it represents the lower limit of absorbed energy. If the air bubble collapsed and all of the sub components were perfectly unharmed, and there is no temperature change in the water, the air volume potential energy would be the exact amount of energy absorbed.

So really the best we can say is that the total energy absorbed in the implosion is somewhere between my number and Tom's number. I would estimate it's closer to the high end of that window, but that's based on nothing other than intuition since we can't calculate the delta T of the water or the energy lost to breaking things.

Quote (The hull material itself does not, because it cannot implode. It's not a matter of semantics.)

I'm not so sure... there is a lot of strain energy stored in the compressed CF material of the hull that would be released. I don't know what the magnitude of this is. The damage caused would be similar to an explosion compression wave, but with a non-compressible fluid, I suspect.

-----*****-----
So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik

The videos, although small scale, show it pretty much just flattens out. Does flattening out a circle into a pancake take that much work?

--Einstein gave the same test to students every year. When asked why he would do something like that, "Because the answers had changed."

Hi dik. Compare the volume of the Cf at the surface to the volume at implosion pressure. Now compare that change in volume to the internal volume of the hull.
I am not disputing that there may be energy stored in the CF. I am trying to quantify that energy.
Intuitively it seems quite small.
There may well have been heat energy released from the ripping apart of the CF, and from breaking the adhesive bonds to the end rings.
However much heat generated, the North Atlantic is a quite good heat sink. (grin)

--------------------
Ohm's law
Not just a good idea;
It's the LAW!

Agreed, waross... I just don't know the relative magnitudes. Even though the volume of the CF was small, I don't know how much energy was stored in it. Like the water compression, this would be given up in a flash (assuming the CF was friable).

-----*****-----
So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik

Quote (Dik)

I'm not so sure... there is a lot of strain energy stored in the compressed CF material of the hull that would be released. I don't know what the magnitude of this is.

The magnitude is effectively zero compared to the implosive energy associated with the collapse of the void.

Thanks...

-----*****-----
So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik

I admire the discussion everyone has provided on the energy released by the implosion and I believe I have followed the logic and calculations on most items except for the expansion of the air volume in the hull after implosion and energy released. If I may indulge everyone's patience:

Quote (SwinnyGG)

If that bubble of air was preserved and allowed to float to the surface, its volume would expand by your 400x multiplier.

Since the air in the submersible is at ~ one atmosphere, at the instant of implosion, wouldn't it very quickly collapse to 1/400 of its volume at STP, then if it were to rise to the surface it would only expand back to its original 8.3 m^3?

Is it appropriate to equate the implosion force to the gas volume generated by TNT?

Though there is the huge reservoir of potential energy in the full height of the water column, isn't the energy of the implosion only the energy required to cause a failure of the cylinder hoop (assuming the hull cylinder failed) and crumple the material. Thus this would be the intrinsic work potential of the material and not necessarily equivalent to the work required to have the volume created by gas volume? The air in the hull is not pressured, so its pressure is not supporting the water column - the hull structure is doing the function. The hull would hold the water column even if there was a perfect vacuum inside the hull, and if imploded there would be no energy calculation of gas volume equivalent at STP but the sudden inflow of water into the hull void would create the shock wave and water hammer that would tear the structure apart? Where am I going astray???

Thanks - this implosion discussion is very amazing.

Run it backwards and see how much Work is required to empty that interior volume at that external pressure. This is what the dynamite comparison example is doing. Whether it is 18 weeks with a hydraulic hand pump or 8 msec with dynamite, the work done is the same. The Power is far different.

If the hull was made of something very rigid and had a vertical cut (the easy way) with a smoothly lubricated surface then the halves could slide and open the interior to the ocean, exposing that void, without any necessary damage to the hull, so it's not a measure of the energy required to cause the hull to fail. Simply having a hatch that opened inwards could allow water in; again, no energy necessarily expended in damage to evaluate the work done.

I believe you are right - the initial air bubble would be reduced 400X by exposure and, as it rose, might regain it's original volume, but it would mostly dissolve into the water and not be a bubble for very long.

Quote (3DDave )

Run it backwards and see how much Work is required to empty that interior volume at that external pressure

Got it! The TNT equivalence is creating filling the void in the water at that incredible ambient pressure. Thanks!!!

I've a better understanding of the calculations and descriptions of the energy involved in the implosion. Amazing and staggering!

One more question, and this may have already been explained, sorry if I am retreading: since the communication between the support ship and Titan was via hydrophones, would not the support ship team have already known an implosion had occurred? It would have been heard by their communication system simultaneously to the instant text messaging was lost. The search effort would have been done just because of the hope the sonic blip of the implosion was an unrelated anomaly?,

Communication was via acoustic modem. The computer on the support ship was listening for the correctly encoded sounds. Implosion isn't one of those sounds.

If you were at your computer in the good old days of acoustic couplers, the guy at the other end would not hear if your house blew up. All he would know is you stopped typing. Ahh, the days when 300 baud was the upgrade.

Thanks 3DDave

Devil is in the details!

I have to smile at remembering the old phone modems: dial up and make sure the phone handset is in the modem cradle!

Any water at pressure or altitude above some datum has potential energy. If it moves, its converting PE to kinetic energy and expending some of it. When it flows downhill (under no pressure) at a steady rate, it is expending exactly what it gained from gravity. Energy loss (ft) == decrease in elevation (ft).

--Einstein gave the same test to students every year. When asked why he would do something like that, "Because the answers had changed."

Quote (when 300 baud was the upgrade.)

I recall the days of the 90 baud acoustic coupler...

-----*****-----
So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik

Never had the 90 baud, but still own a Novation modem, which got rid of the acoustic couplers.

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a real speed demon, as I recall...

-----*****-----
So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik

legal matters

https://www.youtube.com/watch?v=RJQPthD9rx8

-----*****-----
So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik

Something to talk about, the temperature of the implosion.
A diesel engine at idle on a cold day will raise the temperature of the air charge from about 0 degrees C to over 250 degrees c in about 1/2 second, with a compression ratio of 16:1 or less.
What temperature may be reached with a compression ratio of 400:1 ?

--------------------
Ohm's law
Not just a good idea;
It's the LAW!

It's a bit academic, isn't it? The implosion comes with tons of VERY cold water, so whatever temperature there might have been, it's gone in a matter of milliseconds.

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It's a bit academic, isn't it? What's wrong with academic?
Can we look at all aspects of the event?

--------------------
Ohm's law
Not just a good idea;
It's the LAW!

Both good questions... I can answer the last one... absolutely nothing is wrong with academic. My grade 7 teacher had a note on his wall, "The only dumb question is the one unanswered."

-----*****-----
So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik

Temperatures as high as 5000°C for a millisecond or two are produced during cavitation, hence it is very damaging (esp to pump suctions), if it is allowed to continue indefinitely. It is just as effective as a continuous acid wash eating away the exposed surfaces quite effectively.

--Einstein gave the same test to students every year. When asked why he would do something like that, "Because the answers had changed."

For cavitation, is it the temperature? or the impact of the fluid from the opposite side of the 'bubble'? or a mix of both?

-----*****-----
So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik

I'm not sure if it has been exactly determined. My thought is that its just the high total energy impact which ruptures the molecular structure of the surface crystals and strips them away bit by bit. Surely the most common and damaging aspect of pump and maybe ship's propeller operations. Even a small amount of energy is a super high flux, due to the extremely short focus time.

Those pistol shrimp in the link I posted above are deadly. 250dB, twice as loud as a jet engine and 5000°C temps and let there be light. Good thing that they aren't a bit bigger and living in close proximity to humans. It's surely the underwater weapon of choice.

Not sure if this video has made it into the thread yet. I don't recall seeing it. Some good comments from an experienced CF engineer in the comment section too. https://youtu.be/Rn60yfbPFuM

Break time: https://youtu.be/qaeg4Egwnz0

--Einstein gave the same test to students every year. When asked why he would do something like that, "Because the answers had changed."

1503-44 Good YouTube video by Beyond Engineering. There is a lot of junk posted on YT, this video is worth watching.

This follows on the 'shirt tails' of the above youtube and is also interesting... There was a 'deep hole' project when I was in geological engineering called the Moho (sp?) project.

https://www.youtube.com/watch?v=_5Mud1ubq20

-----*****-----
So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik

My question is about the compression/decompression rates of dissimilar materials that are attached to each other. I have no idea, but I imagine that titanium and carbon fiber will compress and decompress at different rates. So could there have been gaps in the titanium/CF interfaces created over time during ascents and descents? And what about the effect of salt water on the bonding material in those gaps?

I think it can be a problem, but it is probably minimuzed when the interface is in compression.

--Einstein gave the same test to students every year. When asked why he would do something like that, "Because the answers had changed."

Quote (Jedidad)

I imagine that titanium and carbon fiber will compress and decompress at different rates.

E for Titanium: ~50 to around 120 GPa, depending on alloy. I suspect an assumption toward the upper and of that range is safe, it's unlikely their domes were pure titanium. I don't believe we know exactly what alloy they used, but I suspect 6Al-4V or something similar. E for low-ox 6AL4V is around 115 GPa.

E for carbon fiber: very reliant on construction. The generic number is around 200GPa, but it can be as high as 500+ GPa.

There's another variable though - stiffness is a function of bulk material properties and section dimensions. I'd argue that for a structure like this, matching strain at design load between mating parts would be a major part of engineering best practices for a safe design. ESPECIALLY if that design involves a field-made adhesive joint. You'd want the absolute lowest possible amount of shear stress on that adhesive to give it any kind of chance.

I'm too lazy to dig out Roark's and look it up, but it's possible that a hemisphere with the edge supported is a stiffer geometry than an edge supported hollow tube, in which case maybe the composite section was strain matched despite the bulk stiffness of the carbon shell being likely much higher than that of the end domes. Given the level of engineering diligence displayed elsewhere, and the fact that the hull components were not all designed by the same firm, I would doubt that level or coordination between mating parts was in place.

I too think the different response of the Ti end caps and CF hull to huge external pressure may have factored in here. If the end caps had more strain, that would have been transferred to the CF, and increased stress there. Or to the epoxy joint.

No substitute for repeated deep dives with monitoring, then dive to failure.

Waross, It's not just 400x compression ratio, but potentially much higher (orders of magnitude more) due to the momentum of the water column accelerating to fill the void, that accelerated water column doesn't just stop at the static pressure equalization, it has to be stopped by an increasingly smaller pocket of air. The bubble/collapse then rebounds several times, decaying in peak pressure/temperature each time. (see first link below) Water hammer is scary stuff. As 1503 said, very high temperatures are instantaneously achieved (not during cavitation per se, but during the collapse and rebound of the cavitation bubble). There is documented release of visible blue light from the point of collapse (sonoluminescence) - see 2nd link.

high speed film of underwater detonations - https://www.youtube.com/watch?v=MPJjMJ48CdY
https://en.wikipedia.org/wiki/Sonoluminescence

Love those older videos. No BS, no narrative, just a really dull narrator backed up with fascinating information.

Quote (Jedidad)

And what about the effect of salt water on the bonding material in those gaps?

Read my previous posting on adhesive bond failure mechanisms and interfacial hydration. Salt exacerbates hydration. So if their surface preparation is deficient, the operating environment will definitely find the deficiencies.

Another issue from the adjacent discussions: There will be thermal stresses generated during the cure cycle due to the different thermal expansion coefficients for CFC and titanium, but there also is a contribution from the relative thicknesses and moduli. It is actually possible to design a bonded joint between thin materials such that the failure will always occur outside the joint. However in this case the CFC is so thick and stiff, that the failure will ALWAYS occur through the adhesive if the surface preparation is valis and resists hydration, but if the surface preparation is inadequate, the failure will occur at the interface, leaving the adhesive layer intact in some regions. This is a very weaK failure mode.

The real issue is that the very thick CFC cylinder butts up to the end cap. I can not conceive of any circumstances where the adhesive between the faces of the CFC and the titanium would survive the extreme compression stresses as the pressure on the end caps is transferred to the CFC shell.Then the next excursion would result in water ingress into the joint. A bit of time between excursions and hydration would ensure that the bond would not survive if the interface is weak.

With some design effort, together with some manufacturing ingenuity, it would possibly have been possible to design the joint such that the adhesive could actually carry the loads. A multiple step fir tree joint may have been capable of carrying the loads. But a single overlap and one step butt joint could never carry the load without the adhesive being the critical element in the joint.

Regards

Blakmax

Quote (blakmax)

...I can not conceive of any circumstances where the adhesive between the faces of the CFC and the titanium would survive the extreme compression stresses as the pressure on the end caps is transferred to the CFC shell...

Just curious, what are typical bearing strengths for engineered epoxies like the Hysol EA9xxx series? In theory the bearing stresses at the interface between the Ti ring and the carbon barrel should be around 20ksi.

You can assume a generic epoxy is going to have a compressive strength of 8,000-10,000 psi. There are varieties that can double those values.

Much depends on the specific product they used.

Other than the compression failure of the epoxy. What effect would that have on the waterproofness of the joint? Wouldn't it simply act as 'filler'?

-----*****-----
So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik

Chockfast Orange comes in at 19,000 psi and it's engineered specifically for compression loading.

19,000?

As I posted above...
Wall stress: 55,000 psi compression-
Long stress: 29,000 psi compression on a 5" thick wall. Someone said the joint might have less bearing surface, which could double that.
Max shear +/-13,000 psi
(neglecting radial stress)

--Einstein gave the same test to students every year. When asked why he would do something like that, "Because the answers had changed."

I updated my cross-section of the hull based on more recent images and videos. Here it is along with some others I have seen:

1 - at top is my latest impression (I think my interface ring is slightly too wide from left to right and I don't think the bolting flanges are necessarily of different widths.)
2 - my earlier design
3 - the NYT's design shown in this article: https://www.nytimes.com/interactive/2023/07/14/us/...
4 - the design from the ANSYS simulation video https://www.youtube.com/watch?v=gzXe9nLy90Y

Not sure if this has been shared yet.

https://www.engineering.com/story/simulation-shows...

While I know very little about this type of structure, the author makes sense.

Quote (rodface)

I updated my cross-section of the hull

Looks pretty close to me- although I think the slot in the intermediate ring is much shallower than that. From the videos of them making up the adhesive joint, it looked like the depth of that feature was maybe 1" at most.

So... from 31ms to 38ms... neat article.

-----*****-----
So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik

Seeing the information above on the underwater explosions reminds me of this video- skip to 9:13 or so to see the effect: https://youtu.be/QA9bOldHoeY
Specifically, he is shooting an oversized rifle into ballistic gel material intended to simulate, to some extent, typical flesh.
Of interest, you can see distinct flashes where the gel rebounds back into the cavity formed even after the bullet is long gone.
This guy has some interesting content if you can overlook some bluster- a lot of his videos are improved by skipping the first minute or so.

On the discussion of strength of the epoxy- concrete strength is considerably higher when confined, although normally measured in an unconfined condition- I wonder if this is taken into account here?

The drawings showing the hull being stepped where it connect to the end rings strike me as bad for several reasons.
If the hull is completely inserted into the groove in the ring, the strength of adhesive becomes less important.
It must hold the structure together on the surface when submerged, it becomes a seal and the water pressure tends to compress it with nowhere to go as it is confined by the ring.
Machining the hull slightly reduces the thickness.
With the end exposed water under pressure may be forced into the carbon fiber.
Once water is forced between the wound layers, it may follow the winding layers deeper and deeper into the thickness of the hull.
Water following the spiral wraps will proceed with both repeated dives and with time at depth, leading to progressive deterioration.
Please tell me that he ends were adequately sealed to prevent water entry.
--------------------
Ohm's law
Not just a good idea;
It's the LAW!

Quote (waross)

Please tell me that he ends were adequately sealed to prevent water entry.

They coated the hull with rhino liner. That's it.

I could see water migrating into the CF hull, either through the sides protected with Rhino Liner (really??), or from the edges where the TI ends glued on.

I do not think Rhino Liner has been tested to be non-permeable at 5000psi.

TigerGuy link has very interesting content and additional discussions on that website.

Quote (waross)

The drawings showing the hull being stepped where it connect to the end rings strike me as bad for several reasons

Yes, the stepped hull doesn't make sense other than to slightly reduce the total OD of the Ti interface rings. Maybe a cost of fabrication consideration? But at the size of the parts and materials being used, this seems unlikely that much cost reduction would have been realized by not enveloping the complete 5 inch thickness of the hull wall.

Anyone taken a shot at understanding the differential diametral strain between the carbon hull and the titanium ring? That they have similar sections and different modulus is a problem.

Having designed a few metal to composite joints, you don't do steps, you do tapered transitions. The 'impedance mismatch' between the stiffness of the two systems needs to be managed. If it were up to me the composite would be left as is and the tapering would be done in the metal.

Cheers

Greg Locock


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Greg, what might that tapering look like? In this case, might it have been mitigated by adding a gradual taper to the inside of the ring, similar to this sketch?

The annular pockets in the interface rings are necessary to prevent putting the epoxy/adhesive joint in shear due to the deflection differential of the Ti interface rings and the CF hull, but inner lip of the pocket creates areas in the CF hull that would have been undergoing not only axial and radial compressive loading but also have bending moments imposed. The inner lips seem to have been rather short for what my gut feel says a longer engagement would have been good.

As I was posting wheaney has put up a great image.

I'm thinking more like this.

@TugboatEng, doesn't the abrupt transition (from right to left) still constitute a sudden mismatch in stiffness of the combined member? I would imagine that the idea of "slimming out" the Ti lip would be to ease the transition and avoid stress concentrations, while still having a low enough profile to be practical.

Yes, the gap in yellow needs to be much wider. This allows the adhesive to absorb the differences in strain. It's no different than an expansion joint. With that said, I don't know that the adhesive is strong enough to withstand the shear forces hence the addition titanium reinforcement underneath in green.



There are still some step transitions. The fir tree joint was mentioned earlier. The key is that the titanium needs to support the end of the cylinder and as designed it doesn't.

Problem 2 is that the joint as designed traps air and epoxy which makes assembly difficult so I eliminated the outer step on the titanium ring in my finger sketch.

The engineering.com article uses images from https://www.youtube.com/watch?v=i-bvNHCCpFo&t=....

However, the simulation's author appears to not have accounted for the images of the recovered wreckage debris, wherein both end rings were recovered, while their simulation shows the end rings breaking. That would have only happened if the adhesive bond with the CF was stronger than the titanium; there's no way the CF implosion could have broken the titanium rings.

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The author of the simulation has another video https://www.youtube.com/watch?v=gzXe9nLy90Y which shows a plan view with the rings breaking, but that's not the way the Titan broke. However, it seems possible that the rings deformed sufficiently that all the bolts broke, but the CF then broke away from the end rings and they regained their original shapes.



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I, too, thought there was something wrong about how the interface rings shattered in the simulation.

I didn't look closely enough to see if the rings had their material set to Titanium or CFRP.

Perhaps he set the strength of the adhesive connecting the Ti to CFRP to be far higher than it was in practice, it was clearly not strong enough to deform and destroy the titanium, it simply let go.

I do believe that as the cylinder imploded, the face contacting the interface ring rotated and peeled the outer lip free, as shown in the debris photos. I think I'll try animating that - see attachment.

https://files.engineering.com/getfile.aspx?folder=...

Given the use of paste adhesive between the ring and cylinder I don't see how they could have been assured of no voids in the bond line. I'd hope they applied clamping pressure between the two, but who knows?

The problem with sloppy work is that the supply FAR EXCEEDS the demand

I am not familiar with details on Abaqus. Does it have exaggeration added to deformations to help visualization? With others mentioning the disconnect between reality and simulation, I have zoomed in on the views and yeah, the interface rings' deflections look a little suspect.

The Engineering .com site has a little background on the hull development:

https://www.engineering.com/story/ill-fated-titan-...

Quote (SnTMan)

...Given the use of paste adhesive between the ring and cylinder I don't see how they could have been assured of no voids in the bond line...

There are common techniques we use to reduce voids and entrapped air when joining assemblies with bonding paste. I was surprised to see in the video that they didn't do any such thing.

hpaircraft what are some of the techniques used?

In my sketch above, I recommended removing the outer ring at the glue joint. This allows the adhesive to flow outwards to removing any voids as it does.

Some other options may include machining a caulking groove into a surface and pumping the adhesive in.

When they set the ring down on the cylinder I would have expected to see squeeze out around the edge. I didn't. Maybe clamp pressure was applied afterwards. Maybe not

The problem with sloppy work is that the supply FAR EXCEEDS the demand

TugboatEng - yes, the outer lip of the interface rings did form a 'void/bubble trap. Perhaps the intent was some form of edge capture for limiting bell-mouthing of the cylindrical ends due to compression of the hull body. But since there were the stepped diameter/hub features adjacent any edge capture just increased load concentration at the diameter transition corners. And the hub features were machine-cut - were the inner corners machined sharp or filetted?

Yes, the red triangle , but with a more sophisticated taper than that, feathering down to nothing. The guy who taught me the practical aspects of CF used to build monocoque motogp motorbike frames.

Cheers

Greg Locock


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A video with some tidbits that I hadn't seen before, including some photos near the end: https://youtu.be/Gm28gju5Brw

Somebody up there mentioned rhino liner- that sounds like truck bed liner or something, so I just assumed that was humor. But no, there's a video clip somewhere of Stockton saying that's what they used. I'm not familiar with the product, so can't comment on the appropriateness of it.

Don't fall for the sensationalism. Rhino liner wasn't a structural component of the hull and PlayStation controllers didn't cause the collapse. Being able to incorporate commercially available components into a design is an engineering talent, not a fault.

I agree, but the controller is not designed for a wet and salty environment. OK, they may well have a spare in a dry-bag, but the same goes for the receiving end of the electronics.

Cheers

Greg Locock


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Quote (TugBoatEng)

Don't fall for the sensationalism. Rhino liner wasn't a structural component of the hull and PlayStation controllers didn't cause the collapse. Being able to incorporate commercially available components into a design is an engineering talent, not a fault.

If Rhino Liner has been tested for permeability under 5000 psi of long term saltwater exposure I'll eat my hat. For a composite hull, especially one with machined end grain directly exposed to full test pressure, protection and sealing against water ingress would be a very important component of the engineering of the hull. The playstation controller had already failed previously, with very dangerous consequences, and provided zero redundancy.

Being able to incorporate commercially available products into a design is a virtue when the selected products are appropriate for their intended service conditions, and don't represent a safety compromise.

Neither of those conditions is true in this case. Both examples serve to provide us significant evidence that the engineering of the complete package was half ass.

Sorry, I'm a bit jaded when it comes to marine hardware. Marine grade does not imply satisfactory duty. Here is a recent example from the best supplier of that equipment. I guess companies with specific products suffer from small engineering teams that may be strong overall but lack knowledge in specific areas. I have some interesting pictures to post of watertight hatches on my boats that I will share tomorrow.



If the sub can surface without the "PlayStation" controller I don't see the issue with using one.

To complicate the story, there isn't really a marine grade. Some items get DMV approval which gives an environmental tolerance rating. None of

Quote (TugBoatEng)

Sorry, I'm a bit jaded when it comes to marine hardware. Marine grade does not imply satisfactory duty

No one said anything about 'marine grade' whatever. The pictures you have of hatches on your boat are meaningless. This sub was not a tugboat.

They used a bunch of completely untested solutions for the problems they were trying to solve. If you're designing a trash can, that's not good engineering, period. In an application involving a major duty to engineer for life safety, especially for paying clients, it is literally criminal negligence.

If this had happened while Rush was on the support ship and 5 other people had been killed, he would be spending a very significant amount of time in prison. Implying that any of these decisions were good is absolutely asinine.

Quote (TugBoatEng)

If the sub can surface without the "PlayStation" controller I don't see the issue with using one.

The sub can't surface if it's fouled on wreckage. If the sub loses attitude and/or directional control, even momentarily, near a shipwreck at 3800m deep and fighting the powerful currents that exist at that depth, there is a high risk that the sub becomes fouled and is either damaged or cannot surface.

Maintaining directional and attitude control at all times is as important for a deep sea submersible intended to explore shipwrecks as it is for an airplane. They went down there using a system that had already demonstrated low reliability through previous failures, and had zero redundancy, and after the previous systematic failure they made zero changes to the system.

Implying that there was any sliver of good engineering here is wild.

The sub wasn't supposed to enter the wreckage. That should eliminate the fouling risk.

My hatch pictures were meant to demonstrate some often misunderstood material limitations. I wasn't trying to explain anything about the wreck, just that the marine industry is plagued with misapplied materials.

The tugboat industry in general is plagued with bad engineering. I am unfortunate that I have to deal with so many problems that I never get to be proficient in them I just have to keep moving on to the next and that's what funds my paycheck. I come here to try to learn better ways to do things.

Quote (TugboatEng)

The sub wasn't supposed to enter the wreckage. That should eliminate the fouling risk.

The sub was most definitely intended to operate in close proximity to the wreckage. It had a viewport for looking at the wreckage, which you can't do from 300m away.

Lose control in the middle of a tour with your billionaire clients and the risk that a current pushes the sub into the wreck and it becomes damaged or fouled is very real. Rush either ignored this risk, or didn't care because somehow using a game controller represented 'innovation', and he was a member of the Silicon Valley culture that values innovation, even false innovation, above all else including good first principles engineering.

Quote (TugboatEng)

the marine industry is plagued with misapplied materials.

We aren't talking about the 'marine industry'. We're talking about one guy, who despite a pretty big pile of highly qualified advice made a bunch of awful choices which resulted in the negligent homicide of four people and his own death. Humans know how to build ultra-deep sea submersibles. There are kind of lots of them that do this stuff without issue. He ignored them out of a killer combination of ego and ignorance, and you're now inexplicably defending the choices he made. The sub is not one of your diesel tugs. Your 'well on my tugboat...' logic that you use in every scenario on this forum does not apply.

Who said I was defending? I was complaining about an industry plagued with poor choices that I struggle to manage. It's frustrating to deal with the low quality equipment but when I see complaints of using consumer grade equipment I understand that may be an upgrade in some instances. We used to use synchros for our azimuthing controllers but have moved to pots. Now we aren't much better than the consumer level electronics. The pot systems have proven reliable over 15 years but the synchro systems have been flawless for 30 years. Good thing as there is no support for the synchro systems.

The newest thing are magnetic rotation sensors. There is one that uses a chip that is operated by moving a magnetic domain so it doesn't require power to maintain the location -and- if the item is moved with the power off, the magnet still moves the domain so it still keeps count within the range. It has 6(?) turn capability.

For sure synchos are less popular now that there are so many A/D converters and digital CPUs, but Analog Devices is making synchro ICs for someone. The controls guys I worked with preferred resolvers for sub-milliradian accuracy and lack of wear failures though those were plenty expensive. Using synchros as direct motion controllers certainly is gone.

What used to take a dozen 8x10 inch circuit boards stuffed with discrete transistors or simple ICs can now be had for $4 and fit on a fingernail. When it cost $20,000 (a new house) spending $500 (newish car) on a decent housing was a no-brainer. That $4 chip still requires a similar level of protection and the cost for low volumes has kept the price about the same, but the bean counters don't see that the failure cost was never $20k and isn't $4, it's millions of dollars when whatever should be controlled no longer is.

I understand that on one trip one of the thrusters was wired backwards and not tested.
The error did not become apparent until they started trying to maneuver at depth.
That thruster was not used when descending and had not been function checked on the surface.
The controller was working but they had to fugure out how to use it with one thruster reversed.
Was there a game controller failure that I am not aware of?
PS; I'm not defending the controller.

--------------------
Ohm's law
Not just a good idea;
It's the LAW!

My understanding was that the controller to motor wiring was reversed on one thruster. Apparently reversing a jumper at the controller "fixed" that problem, although the real problem from my perspective was nobody realized that problem existed until it was in the water. If any control were reversed on my ultralight airplane, I would have discovered it during preflight check. There it must have been like ... splash. Not really a controller, or motor problem at all. That was only a symptom of the true problem.

--Einstein gave the same test to students every year. When asked why he would do something like that, "Because the answers had changed."

There have been a large number of cases where ailerons were reversed, up to and including the A320. People check to see if they move; not all check to see if they move correctly, not even licensed aircraft mechanics.

The write-ups indicate it had just been mounted and they installed it pointing in the wrong direction.

In this article are several photos - note that the orientation of the starboard fore/aft thruster changes from the motor being forward to the motor being aft. The port motor is forward of the duct. https://www.slashgear.com/1319049/missing-titanic-...

It's entirely possible someone programmed the motor direction to match one configuration and Rush changed his mind. The thrusters appear to be clamped on the rim and easily placed in either orientation with sufficient length of cable. On the top it appears they sometimes just doubled up excess cable length.

In later versions the thrusters go into pods and the motors are placed to the rear of the duct/sub.

Here's another - starboard motor to the rear https://curlytales.com/another-day-another-revelat...
At the 15 second mark of this video the starboard motor is to the front: https://www.engineering.com/story/was-the-oceangat...

I always checked direction of travel, but I may be a bit paranoid.

--Einstein gave the same test to students every year. When asked why he would do something like that, "Because the answers had changed."

Checking control freedom and correct action is nothing more than proper pre-flight procedure.

"Schiefgehen wird, was schiefgehen kann" - das Murphygesetz

Quote (TugboatEng)

Who said I was defending?

No one said you are defending - it's not implied. It is literally your direct response to a comment which pretty gently questioned the decision to use rhino liner to coat the hull - which against is completely untested solution for a critical aspect of the hull design.

Quote (TugboatEng)

Don't fall for the sensationalism. Rhino liner wasn't a structural component of the hull and PlayStation controllers didn't cause the collapse. Being able to incorporate commercially available components into a design is an engineering talent, not a fault.

Tug, that connection looks exactly like the “watertight” connection to my pool robot. Hence the advice to never leave the robot in the pool.

Quote (TugboatEng)

Rhino liner wasn't a structural component of the hull …

Not directly, but it could possibly be considered holistically critical to the structure. If sealing the outer surface of the CF against the 5500psi seawater is critical to the integrity and longevity of the structure, it does become a critical part of the structural design, despite not adding significant strength or rigidity.

Personally, I think I'd have chosen something like one of the epoxy hull primer/filler products from International, rather than Rhino; for an outer coating to seal and protect the CF. They won't be rated for use at extreme pressure, but likely would form a good bond with the CF.

I have had a week off travelling... a benefit reserved for the retired. I note the simulation provided by IRStuff, and I make the comment that this representation depends yet again on the composite failure theory used in the model. Again, if it is the Tsai-Hill or Tsai-Wu model the results is totally fictitious.

With regard to the ability of the adhesive to transfer sufficient load to enable the titanium to fracture rather than the adhesive, that is totally incredible. The load capacity of an adhesive bond depends upon the relative stiffness of the adherends (EiTi/Eoto) and I can assure readers that a 5 inch thick CF structure will always cause the adhesive to be the critical member.

The other question that must be asked is the design methodology for the adhesive joint. There is a common belief that the "strength" of a bonded joint is measured by a lap-shear test such as ASTM D1002. That test does NOT under any circumstances generate design data. That test typically uses a standard thickness of adherends and a standard overlap length. Change any single parameter and the results will change. Unless the design matches the specimen geometry any prediction of bond strength on the basis of lap-shear strength is totally meaningless, especially using FEM analysis.

The other issue is that adhesives are dominated by elastic-plastic behaviour, not just elastic behaviour. Typically up to 60% of the strain energy to failure is plastic behaviour. So taking a badly derived allowable strength from a lap-shear test and using an elastic analysis (typical of FEM) to predict strength will have little relevance to the actual structural strength.

Next, is the relationship between temperature and adhesive strength.Adhesive properties change significantly with temperature; high temperatures result in low shear modulus, low plastic strength but high strain to failure. Low temperatures cause high shear modulus, high plastic strength but low strain to failure. Unless your FEM actually uses data at the relevant temperature, and unless the analysis has an elastic-plastic capability (rare) then your bond strength estimates have very little relevance to reality.

Next, while Tugboat's suggested modification of the overlap has some merit, in practice unless there is some symmetry in the joint (fir tree joint or extended double overlap design) there will always be a very significant bending moment generated by the mis-alignment of neutral axes and that will always risk failure of the vertical bond face, and a5 inch thick CF structure will almost certainly result in tensile stresses at surface loads and temperatures. I suspect that the only viable configuration would be a fir tree joint, but that would need careful manufacturing procedures to generate the structure in practice.

Blakmax

Wow.

I didn't mean to kill the discussion with my last posting!!! Sorry Guys and Gals.

My background: I have been working in composites and adhesive bonding since 1972. (I think Moses was still in shorts then.) I am well and truely retired but I have extensive experience and expertise in composite and adhesive bond failure forensics, and a different perspective on adhesive bond damage tolerance than the usual accepted mantra that fails to distinguish between analysis of defects that may lead to cohesion failure at high loads and those that result from weaker mixed-mode failure and very weak adhesion failure. I spent years between 2013 and 2020 delivering courses on this technology, until COVID stopped my activities. I am now almost 76, and I would re4ally like to pass on my knowledge to the wider adhesives and composites community.

In the current discussion WRT the submersible, there are many issues yet to be examined. For example,
What was the surface treatment for the titanium surfaces prior to bonding?

Were there appropriate tests to assess hydration resistance provided by those treatments?

Importantly, all fibres are treated with a "size" to prevent damage during manufacture. It is essential that that size material must be compatible with the resin system such that the fibres bond to the resin. In compatibility will result in adhesion failure between the fibre and the resin with a loss of shear, tension and compression strengths. I have seen examples of this problem that resulted in substantial reduction in component service life.

We don't know if or how the finished CF shell was checked with NDT, and if any defects found were "repaired". Those who know me know very well my opinions on "injection repairs". (you only achieve two things by injecting fresh resin or adhesive into a void: You hide the defect so that NDT can no longer detect the air gap, and you get a warm fuzzy feeling that you have fixed the problem. The surfaces of the voids are chemically fully reacted, so you can never achieve a viable bond.)

So my questions to the discussion group are:

Would it be of value if I placed my lecture notes for my course for open access?
If so, where should I post the files?

I have often said that with composites and adhesive bonding, it is a stupid ass that trips on the same stone twice. I reiterate the point that deciding to use cheap inexperienced engineers so that you do not inhibit free thinking really leaves you open to being an ass. EEAAW EEAA Eawlways says that!

Regards

Blakamx

I don't think you killed the discussion... there's just not a ton of new information and everything that's publicly available we've already steamrolled in the discussion. I expect if/when new information is made public this thread will get hot again.

Quote (blakmax)

What was the surface treatment for the titanium surfaces prior to bonding?

There are a couple of paths to activating titanium and/or resin surfaces to prepare for adhesive bonding (based on your stated experience, expect you're well aware of this already). At this point, I think the group consensus is that we suspect none was used, but we can't prove that conclusively.

Quote (blakmax)

Were there appropriate tests to assess hydration resistance provided by those treatments?

Similar to the above... I think we all suspect the answer is no (I certainly do) but we can't prove it.

Quote (blakmax)

Importantly, all fibres are treated with a "size" to prevent damage during manufacture.........

Quote (blakmax)

We don't know if or how the finished CF shell was checked with NDT, and if any defects found were "repaired".

Given that the hull was wound by a very reputable and experienced manufacturer of composite structures, I still maintain that failures due to a deviation from standard practices in the carbon fiber section itself are not likely. Certainly possible, but not likely. The most likely failure mode in my opinion is at the adhesive joint, and is due to design errors by the OceanGate team and not by the manufacturer of any one component of the hull.

But, maybe with your experience you can answer a question I've been thinking over... my understanding is that the composite house was given specifications on maximum pressure limits etc to design the composite section against. Also that they are highly experienced and well reputed for filament wound structures, but not for filament-wound structures for high pressure underwater applications. I tend to lay blame at the feet of the OceanGate staff for selecting the wrong material for the application, and then dictating design terms to the composite manufacturer, who essentially just 'followed the drawing'.

Question is, in the world of commercial composite structures, would thorough NDT be expected as part of their in-house quality control process, regardless of whether or not it was specified by the client, or is that the sort of thing that you would expect to only receive if it was directed on plans/by contract?

I have been running on the assumption that any specific porosity/density requirements needed to be directly specified by the OceanGate engineers, and that if the composite hull section was not heavily inspected via ultrasound or whatever, it is simply because the OceanGate team failed to specify quality requirements correctly.

Quote (blakmax)

We don't know if or how the finished CF shell was checked with NDT, and if any defects found were "repaired".

We know that Stockton Rush fired his chief engineer (and threatened him with a lawsuit if he talked) for suggesting the sub was unsafe to dive unless periodic NDT was performed.

Would love to see the course notes, and to have them preserved for future engineer's use. Dunno where they could be kept though.

Quote (btrueblood)

We know that Stockton Rush fired his chief engineer (and threatened him with a lawsuit if he talked) for suggesting the sub was unsafe to dive unless periodic NDT was performed.

Fair point, I had forgotten about that wrinkle in the chief engineer saga when I typed my long response above.

If I'm remembering correctly, though (feel free to correct me otherwise...) that was in the context of ongoing NDT to continuously check the hull for accumulated damage, and not necessarily a one-time NDT check of the completed part prior to accepting it from the manufacturer. Maybe I'm remembering wrong or maybe it wasn't clear in the history we have available.

Quote:

I still maintain that failures due to a deviation from standard practices in the carbon fiber section itself are not likely.

That's a pure speculation since the manufacturer simply wound to Oceangate's (Rush's) specifications; if they were insufficient, which is a highly probable case, then it most definitely could have been simple failure of the composite, even as the manufacturer did everything to industry practice. Oceangate did no testing whatsoever to validate their design concept of using that specific winding approach and thickness of the finished winding.

TTFN (ta ta for now)
I can do absolutely anything. I'm an expert! https://www.youtube.com/watch?v=BKorP55Aqvg
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I don't think the guy that was fired was the chief engineer, more like the chief pilot.
There are quite a few videos on Youtube relating to this, but mostly all just rehashing the same limited information.
It seems obvious that there are quite few issues that COULD have caused the failure.
And I expect here in a few months or year or whatever, the NTSB or whoever else will opine on what DID cause the failure.

One issue that I've not seen addressed. There was a supposed leak of the transcript between submersible and surface (with some speculation as to whether or not it was genuine). Assuming it is genuine, one item of concern there was that when they tried to surface, and jettisoned everything they could, they were still barely moving upward. So either some kind of miscalculation on the weight had taken place, or some space had flooded that wasn't meant to flood. Or maybe the CF became waterlogged, if that's possible? Anyway, that seems a most curious occurrence and makes me wonder what the heck was going on there.

Any continued discussion of the 'leaked' transcript seems to me to be wasted effort and falsely adds validity to specious data. If that transcript had any validity, corroboration to known sources would be available. That whole thing is/was to drive activity to a YouTube channel to generate views and ad dollars. Shameful monetization of a tragedy . . .

Quote (IRStuff)

That's a pure speculation since the manufacturer simply wound to Oceangate's (Rush's) specifications; if they were insufficient, which is a highly probable case, then it most definitely could have been simple failure of the composite

Yep, agree that I'm speculating. I'm not saying the carbon fiber didn't fail, I'm just saying that I suspect if it did fail it wasn't due to defects outside of what would be expected to occur during production of a filament wound carbon fiber part adhering to industry standard best practices for that construction.

We're saying the same thing though. What I mean is that my suspicion is that the hull was likely correctly manufactured, per the normal best practices of the filament wound carbon fiber structure process - but that it was correctly manufactured according to a bad design.

Part was built correctly, to match a drawing that was wrong. IE it's likely a failure due to OceanGate's design process, and not a manufacturing error during production. That's based on the assumption that OceanGate's contract with the manufacturer was 'build this filament wound carbon thing according to this specification which we came up with'. That's a lot different than 'design and build a carbon fiber filament wound hull section for a 4,000m submarine, and include all engineering to ensure long term durability under exposure to deep sea submerged conditions'. We don't know for sure, but based on the information we have so far it seems that the arrangement was #1 and not #2.

@blakmax

I personally would very much appreciate being able to read your lecture notes. Your expertise is evident in your posts here, and the few papers that you have linked to in the past.

I commend your willingness to pass your accumulated experience and knowledge along to the rest of us.

As for where:

Did you lecture in association with an association, or a university? If so, do they have a suitable web place for your notes?

You could create your own website, blog etc. and post there, although that might cause more effort and recurring cost then you care to take on.

You might find a good home at one of the places listed here: https://en.wikipedia.org/wiki/OpenCourseWare

I'm interested. I am proposing an adhesive option to mount various markings underwater on steel vessels. It's similar to draft markings. I need something that tolerated permanent immersion with SSPC SP-3 prep. I'm looking at acrylic adhesives due to the large number of installations. I'm curious about primers to prevent hydration. I keep seeing interesting things about siloxanes.

Hi MintJulep

In 2006, I was engaged as a consultant to a helicopter crash in Fiji. It occurred on the same day as there was a military coup and therefore the Australian and New Zealand governments withdrew the usual formal investigative support from government organisations, so CAAFI engaged a consultant who became frustrated with the advice from industry companies involved with helicopter maintenance and through a contact in the NZ Defence Testing Authority, he contacted me while I was working with the Australian Air Force. In 1996, the FAA conducted a review of 36 crashes of this particular type of helicopter, and they could not find a common cause.
The Investigator In Charge had eliminated the usual causes but could not exclude failure of the main rotor blade.

Within one day of examining the wreckage in Fiji, I advised the IIC of what was the probable cause of the blade failure, based on my experience with failure assessment of bond failures on RAAF F-111 structural construction methods and repairs. My findings were supported by the NTSC investigations and my curse work was a result of collaboration between my company Adhesion Associates P/L (now closed) and the FAA. I acknowledge the support of the FAA and EASA in the support of delivery and development of my course.

As background, in 1992 I had undertaken an assessment of adhesive bonded repairs and found that 40% of repairs repeated the same deficient practices (Donkey, same stone...). With regulatory support, we changed the surface preparation process to address hydration resistance. We improved training such that the technicians understood the fundamental mechanisms of adhesion such that they also understood the consequences of shortcuts in process procedures. We also changed the adhesive used for repairs. Now, changing the adhesive does not make the fantastic difference that adhesive salesmen would have you believe, but in our case the colour of the different adhesives enabled us to be sure of the period when repairs were performed. Between 1992 and 2007 when I retired from RAAF employment, the repeat repair rate fell from 40% to 0.06% and because of the quality management systems we had established, we could tell exactly where the technician had taken a short cut.

To be honest, the many years of implementation of bad technology has generated a poor opinion of a really good technology which if implemented correctly could dramatically improve structural integrity. What is needed is education of how adhesive bonds from and in particular, the causes of adhesive bond failures both short term and long term. I'll take your advice about the web site.

Thanks

Max

It would be appreciated here, too... thanks, Dik

-----*****-----
So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik

What a crap post, dik. Reported.

Post deleted, but, pretty much what I expected... and in milliseconds.

-----*****-----
So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik

One of the things that makes this story of interest is that it is considerably out of our normal realm of experience. I'm not sure if anyone has actually witnessed, by video or other means, the actual implosion of something this size under this much pressure. And I don't know that anyone has actually examined the aftermath of a similar implosion under this much pressure- other submarine failures have presumably been much shallower, with more ductile hulls. So the question of "what exactly happens to the people" is bound to come up. I think earlier in the discussion was the assertion that there would be no remains recovered, followed some time later by the reported recovery of remains, so apparently there are some unknowns even on that aspect.

Without getting ghoulish "remains" means some matter which is identifiable at microscopic level as human tissue or bone fragments.

Not like digging up a shallow grave.

Airplane high speed crashes like we've seen recently are exactly the same. Think Of that German Wings plane which deliberately nose dived into the ground at 500 MPH in France. That's what the rescue teams have to deal with. People are essentially some solid and fibrous mass with a lot of water. The water would go away but the other mass remains, just not in any recognisable form. That's my understanding at least.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

The simulation seems to mimic an explosion, rather than a body.
A slow application of pressure will compress the air in the lungs, throat, etc and any gas in the intestines.
The body will collapse but still be recognizable.
We have all seen movies where a body explodes in a decompression chamber.
That is when the pressure is released, not when the pressure is applied.
Is it reasonable that the inertia of the imploding water will generate a great enough transient over-pressure that the release of that transient will cause a complete disintegration of the body?
I would expect that the limbs may be much less affected than the torso.
And, yes I realize, that this just addresses the pressure effects and does not account for debris impacting the bodies.

--------------------
Ohm's law
Not just a good idea;
It's the LAW!

Waross...human body does not resist water pressure transients. Every individual cell and enclosed structure imploded then anything remaining exploded. Nothing but soup. Basically indistinguishable from the surrounding mud, unless you have a mass spectrometer. Put a raspberry and 100ml of water in the blender.

--Einstein gave the same test to students every year. When asked why he would do something like that, "Because the answers had changed."

Quote (SwinnyGG)

...Given that the hull was wound by a very reputable and experienced manufacturer of composite structures, I still maintain that failures due to a deviation from standard practices in the carbon fiber section itself are not likely. Certainly possible, but not likely...

Except, of course, the fact that according to design tools developed and used by folks who actually make DSVs, they used less than half as much carbon fiber as they ought for the specified parameters and safety factor. As discussed earlier (might be in Part 1), according to the CET tool, for a safety factor of 2.25 their hull should have been 11.5" thick. Their actual 5" thick hull, if properly made, would only have had a safety factor of 1.3. And I suspect that the noises it is reported to have made had something to do with the actual safety factor being subunity.

https://www.compositeenergytechnologies.com/underw...

Quote (hpaircraft)

Except, of course, the fact that according to design tools developed and used by folks who actually make DSVs

Right, but the manufacturer of the hull didn't design the hull.

Design scope and manufacturing scope were separate parties. All I'm saying is that I suspect (can't confirm. Suspect.) that this is a case where a part was made which conformed with the drawings, but the drawings were wrong.

Quote (SwinnyGG)

Right, but the manufacturer of the hull didn't design the hull.

As reported in Composites World:

Quote:

...Spencer Composites’ president Brian Spencer signed a contract with OceanGate for the Cyclops 2 hull in early January 2017 and was presented with very basic — but challenging — performance parameters: Length, 2,540 mm; outside diameter, 1,676 mm; service pressure, 6,600 psi; pressure safety factor, 2.25. “They basically said, ‘This is the pressure we have to meet, this is the factor of safety, this is the basic envelope. Go design and build it,’” Spencer reports. And he was given six weeks in which to do it....

The operant part of that snippet is the direct quote from Mr. Spencer. It seems odd to me that they were given an OD not an ID to design to, but that's what's in the article. I have to assume that at least the direct quote is accurate.

Ok, this discussion is all just wild speculation.

We don't know who built the actual composite cylinder that failed (that entity has wisely kept VERY quiet).
We don't know what materials were used in the composite cylinder that failed.
We don't know who designed the composite cylinder that failed, nor how they designed it.
We don't know who bonded the Ti end rings to the cylinder, nor what adhesive was used, nor what surface prep was used (if any), nor how the adhesive was cured, nor what the actual joint configuration was (though there is some speculation above based on some poor quality photos.

But the first composite cylinder built by Spencer Composites (see the Composites World article referenced somewhere above) was designed with a rubbish failure criteria, using who knows what material properties (likely some vendor datasheet values), and likely did not account for fiber waviness in the cured cylinder which would be expected for a 5" cylinder (for some info on potential effects of waviness see this paper: https://journals.sagepub.com/doi/10.1177/073168449... )
And that first cylinder was apparently fabricated with a mix of wet layup plies for hoop direction fibers and prepreg plies for axial direction plies, so likely two different resin systems with who knows what effect on final properties (no way in hell I would do that mix without a ton of test data behind it).

Then the online video of the bonding "process" may or may not have been used for the cylinder that failed. But that "process" was not done in a clean room, did not appear to have any means of adhesive thickness control, did not appear to have any means to ensure lack of voids or other defects in the bond (all of which violate best practices learned the hard way over the years). And then the joint configuration seems to have a rabbet machined into the composite cylinder, which is insanity for this design - it creates a large stress concentration to create a delamination in the laminate. And while the joint "designer" probably assumed that the "bond" was just to "seal" the connection between the Ti and composites as the joint would be in axial compression under pressure load, they probably did not consider the stiffness and CTE differences between the two parts nor the effects of repeated load cycles on the "bond".

And lastly the arrogant reliance on "structural health monitoring" to ensure "safety" is use of a completely unproven and likely unsuitable technology, particularly for this application.

Quote (hpaircraft)

The operant part of that snippet is the direct quote from Mr. Spencer. It seems odd to me that they were given an OD not an ID to design to, but that's what's in the article. I have to assume that at least the direct quote is accurate.

Fair enough - this is information I wasn't aware of. I stand corrected. If that was the same process shared for the second hull which failed, sounds like Spencer Composites probably has some responsibility here as well.

I'm wth you SWComposites. There is a lot we don't know but what we do know is very curious indeed. Your most telling comment was :

Quote (SWComposites)

And lastly the arrogant reliance on "structural health monitoring" to ensure "safety" is use of a completely unproven and likely unsuitable technology, particularly for this application.

As previously discussed I don't think the passengers would have had time to discuss the last acoustic indication of structural activities.

There are3 so many factors with relation to design of the composite structure, design of the adhesive joint, composite manufacture, surface preparation, cure cycle management for the composite and the adhesive, there are many aspects of this project that one could readily attach the adjective "cowboy" to many of these aspects.

Has ANY of the composite structure been recovered?

Blax

Given that they only recovered one of the endcaps, I'd say no, particularly since the composite was the most likely to be completely disintegrated.

The original hull appeared to have a titanium spool upon which the composite was wound, but the new one either didn't or it was removed after winding.

TTFN (ta ta for now)
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The New Yorker magazine has a very detailed story on OceanGate and describes many of the items David Lochridge was concerned about and insights into the operations at OG. The magazine website has a paywall but I believe you can view a limited number stories before a subscription is required.

https://www.newyorker.com/news/a-reporter-at-large...

It is rather disappointing to read some parts as it is apparent Stockton Rush really did not apply his engineering knowledge on many aspects of the development of the Titan submersible to ensure safety. He really got hell bent on achieving his vision on submersible design. As others have already noted, Stockton was free to risk his own life as he so wished, but he crossed a moral and ethical line by using deception on the safety of the sub's design and put other people's lives at risk. The whole engineering leadership/team at OceanGate is culpable as well. They must be bearing an extreme load of guilt. If not, they are really callous.

Quote:

he crossed a moral and ethical line by using deception on the safety of the sub's design and put other people's lives at risk.

We don't know what he actually believed; even the most technical people can self-delude. He might have truly bought into the notion that everyone else in the world was wrong and he was the only one that was right, and that his craft was not risky. After all, he piloted the Titan himself, and unless he had a death-wish, he would not have knowingly risked his own life unless he was just cuckoo.

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IRStuff yes, you are correct, I cannot say Stockton willing deceived anyone. He and/or the OceanGate engineering team definitely ignored many red flags. I previously defended his actions because he did pilot the Titan and that indicated he trusted the engineering, assembly and materials - total respect for those who build and pilot their own airplanes, subs, and rockets! But yet there seems to be information missing on where his confidence came from. OceanGate engineering studies and test results? Contracted design and FEA? Industry guidance papers? (Likely not) I don't think he had a death wish but he trusted the sub and appears to have bulldozed anyone who was contrary to his opinion.

I used to be a firm believer that the objective truth would be easy to see, particularly for engineers, but it's become obvious that biases and beliefs can run roughshod over objective truth and lead to fallacious conclusions. Rush argued that regulations and testing weren't necessary because most incidents were not due to structural issues and therefore such regulation was overly burdensome and stifling innovation; but his biases failed to see that correlation was not causation, and it was the burdensome regulation and testing that prevented the structural failures so that all was left were the human factors. It's indeed sad that people died because of his delusions.

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Quote (IRStuff)

The original hull appeared to have a titanium spool upon which the composite was wound, but the new one either didn't or it was removed after winding.

Both were mandrel wound, mandrels removed after autoclaving.

Quote (Brian Malone)

The original hull appeared to have a titanium spool upon which the composite was wound, but the new one either didn't or it was removed after winding.

My read on this was/is that while he had some engineering training and worked in engineering-adjacent fields (he was apparently briefly a test engineer on the F15 program in the early 80s), it seems like a case of someone who had some engineering training and experience but worked on an assumption that because they had experience in one field, that experience applied equally to all fields. Speculation of course.

So far there has not been any indication Ocean Gate ran any full-scale tests to failure to check their design calcs and verify the capability of their Real Time Hull Monitor system - thus, it does appear Stockton Rush did suffer some self-delusion on the safety of the sub's design. Ego can only provide so much confidence - something else fuelled his trust in the sub. After a few successful dives did he become totally complacent to the magnitude of the force involved with an implosion? You guys have provided the calculations and analogs that show tickling the implosion dragon is/was not smart! Did his misplaced confidence and academic credentials and strong personality kowtow the rest of the OG engineering team (except David Lochridge)? Mention has been made of the team having young possibly less experienced engineers, but was this true for the whole team? The director of engineering, Tony Nissen, is no neophyte. The New Yorker story does indicate at least one member of the board of directors used his Coast Guard expertise to craft the business model to slide through regulatory loopholes. The BOD probably was on board and with confidence expressed and supported by top management the stage was set for tragedy. Certainly, not all BODs are technically astute or totally savvy to all company operations but if there was concern from the BOD it probably was minor. If there was an error of group think at OG then it parallels the error mode created by Denney Pate and the FIU pedestrian bridge failure.

Quote:

while he had some engineering training and worked in engineering-adjacent fields

He supposedly graduated from Princeton with a BS in Aerospace Engineering, so ostensibly had gone whatever the math and physics requirements were. Of course "Cee's get degrees" so we don't know whether he was a diligent student or not.

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If he paid attention in his classes, he would have understood the cumulative effects of material fatigue. There is a reason passenger jets are in service for a limited time. Just like plane wings, titanium and carbon fiber do not self-repair after they crack.

I do see fatigue being mentioned a lot. One thing to consider is that the number of cycles may not be relevant if this were a creep related failure. And that case, time spent at depth would be a greater contributing factor. Carbon fiber itself may not be sensitive to creep, but when you load composite structures and compression, the resins are forced to hold the fibers together. Together. In this case, the resin may have been sensitive to creep.

On that note, I wonder how an unreinforced acrylic cylinder would perform versus the carbon fiber in the similar situation.

I'm not familiar with it... the only guy I know that is, and this was the subject of his PhD thesis. He has not responded to my query (maybe for a good reason). I gather that CF is really susceptible to internal flaws.

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Quote (TugboatEng)

I wonder how an unreinforced acrylic cylinder would perform

UTS of cast acrylic is only around 10,000 psi... I'm sure you could make a hull big enough to hold a person out of purely acrylic, but the wall thickness would have to be pretty crazy

If such a water-clear acrylic hull could be fabricated, the view would be wild!

I read an interesting piece today in Vanity Fair. I'd post a link but I just burned up my free article. Now behind a paywall for me.

A few interesting take-aways:

1. There were basically no substantial pieces of CF found in the wreckage. They picked up some shards, that is it.
2. Some of the Ti pieces were "bent".

3. Very little to no CF left adhering to the Ti pieces.

Going off memory from this morning, so may not have the quotes exactly right.

https://www.vanityfair.com/news/2023/08/titan-subm...

TLDR, but your bullet points mostly match the article, but didn't see anything where they recovered any shards of CF, just the following

Quote (https://www.vanityfair.com/news/2023/08/titan-subm...)

“There was no piece I saw anywhere that had its original five-inch thickness,” he said. “Just shards and bits…. It was truly catastrophic. It was shredded.”

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Swinny, I read that the compressive strength of carbon fiber is quite low, maybe 10% of a UTS of 175ksi. Meanwhile, acrylic can have a compressive strength upwards of 18ksi. That's why I had the thought that they may have been better off building the tube out of acrylic, possibly even with the same dimensions. The fiber reinforcement doesn't have much contribution to compressive strength, think of each fiber as a very slender column. The fiber does reduce the effects of creep which may allow the structure to operate at loads closer to it's ultimate strength.

Apparently, acrylic turns opaque before it fails so if their submarine suddenly turns white it's time to get back to the surface. Maybe this is more reliable than listening for popping sounds.

compressive strength of carbon fiber is quite low, maybe 10% of a UTS of 175ksi. Absolutely wrong. We have used carbon fiber composites in aircraft structures for 40+ years, including 787 and A350 fuselages and wings, both which have significant compression loads. One just has to known what they are doing, and have appropriate test data.

That article is terrifying.

A quote from Lochridge on inspecting the submersible prior to its first dive:

Quote (Lochridge, VF article by S. Casey)

"The carbon fiber filament was visibly coming apart, riddled with air gaps, delaminations, and Swiss cheese holes—and there was no way to fix that short of tossing the hull in a dumpster."

and further:

Quote (Lochridge, Vanity Fair article by S. Casey)

“Non-destructive inspection is required to be undertaken and subsequent results provided to myself prior to any in water Manned Dives commencing,” he added, digging in his heels on the scanning. This would reveal any weak spots and provide a baseline that could then be used to check for signs of fatigue after every dive.

Scanning the hull shouldn’t be a problem, should it? Lochridge noted in another document that OceanGate had previously stated the hull would be scanned. (Spoiler alert: The hull was never scanned. “The OceanGate engineering team does not plan to obtain a hull scan and does not believe the same to be readily available or particularly effective in any event,” the company’s lawyer, Thomas Gilman, wrote in March 2018. Instead, OceanGate would rely on “acoustic monitoring”—sensors on the Titan’s hull that would emit an alarm when the carbon fiber filaments were audibly breaking.)

Oceangate subsequently fired Lochridge and then sued him, mostly to shut him up.

Quote:

He might have truly bought into the notion that everyone else in the world was wrong and he was the only one that was right, and that his craft was not risky

I think that's very likely given that, as you say, he was on board himself

March 2018 news story from a Everett, WA area TV station:

https://komonews.com/news/local/everett-based-comp...

Tony Nissen, director of engineering, with the Titan.

Quote (TugboatEng)

I read that the compressive strength of carbon fiber is quite low, maybe 10% of a UTS of 175ksi

It's more like 50% or so. We'd be able to put a pretty good number on that value if we knew the combination of materials used.

Yes, I'm making a big assumption with the acrylic adhesives and resins. They are certainly the most tolerant to application and error which is why I assume they are what was used. I called two specific application errors on day 1.

I am no stress analysis type engr, but on that 5" thick CF cylinder in compression, are the stresses uniform throughout the laminate? I think not, but too lazy to research it.

I know our Navy subs use ribs internal to the pressure hull.

Wonder if this thing could have been built up with prefab CF ribs and then hull wound around them. The inside surface of the rib would be in tension where CF shines and hull could be thinner. But still hull would have to take the compressive forces from the end caps...

Just thinking aloud...

no ribs whatsoever; that's evident from the YouTube videos on the winding process.

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Yea, I know it did not have ribs. Just wondering if ribs would have made a better design.

Solid carbon fiber would have worked, except for the passengers.

Ribs in submarines are there to prevent oil-canning, where local deformation leads to global buckling.

This appears to be compressive buckling - if ribs could be in tension they would add to the compressive load in the hull, causing it to to buckle sooner.

What was needed was a reduction in compressive stress by making the wall much thicker. Local reinforcement produces stress concentrations, unless the designer is very careful, which this guy was not.

3DDave,

what would have helped even more was a better composite failure criteria than the commonly accepted Tsai Hill or Tsai Wu criteria that are widely programmed into many FEA packages. FROM MEMORY: (and it is a 75 year old memory!!) there was a widespread assessment of composite failure criteria conducted by the International Conference on Composite Materials (ICCM) in the3 early 2000's whereby candidates were invited to submit strength assessments for known but undisclosed test results. Candidates were asked to provide predictions based on known material data, lay-up details and given loading conditions. I may be wrong, but my memory was that the above failure theories were unconservative for compression-compression loading by a very significant factor (from memory it was about eight).

Quote (Lochridge, VF article by S. Casey)
"The carbon fiber filament was visibly coming apart, riddled with air gaps, delaminations, and Swiss cheese holes—and there was no way to fix that short of tossing the hull in a dumpster."

If this quote is valid, then the issue of failure criteria would then impinge on damage tolerance considerations. Fr goodness sake I really hope that they didn't use "injection repairs" to correct the defects. I have alw3ays said that you only achieve two things from injecting fresh resin into a defect: 1. you hide the defect so that NDT or visual inspection can not find it, and 2. you get a warm fuzzy feeling that you have repaired toe problem. The difference in strength is dead set zero. During the cure cycle the surface of any void is fully reacted out, so the surface of the void is not capable of reacting with the fresh resin, so no bond is formed. I am astounded that almost every composite manufacture still uses this technique. It HIDES the defect, but it does not REPAIR it!

Blakmax

Anyone wanting to go down the wormhole of composite failure theory madness should start with these two papers:

Recommendations for designers and researchers resulting from the world-wide failure exercise, P.D. Soden, A.S. Kaddour, M.J. Hinton, Composites Science and Technology 64 (2004) 589–604

A comparison of the predictive capabilities of current failure theories for composite laminates, judged against experimental evidence, M.J. Hinton, A.S. Kaddour, P.D. Soden, Composites Science and Technology 62 (2002) 1725–1797

And Max I completely agree with your comments about "injection repairs", but I doubt they tried that on a large 5" thick part.

Tony Nissen left Ocean Gate in 2019, some time after David Lochridge was fired in 2018.

The hull that Lochridge was concerned about was the original Titan hull, which was replaced in 2021.

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Yes, so the provenance of the hull that failed is an unknown. Probably not made by Spenser Composites, Possibly, Electro Impact or Janicki.

Quote (blakmax)

I really hope that they didn't use "injection repairs"....The difference in strength is dead set zero.....I am astounded that almost every composite manufacture still uses this technique.

What's your basis for claiming that? I did a quick google search and it seems a commonly used method with experimentally proven results. One such example:

https://www.nxtbook.com/nxtbooks/sampe/journal_201...

From the charts in that link it appears that all cases converge quite closely on the right side which indicates that there is no difference between repaired and unrepaired.

Quote (Tug)

which indicates that there is no difference between repaired and unrepaired.

That's well past ultimate. At ultimate load there is a marked difference between repaired and unrepaired.

Tomfh

My assertion that injection repairs are ineffective is based on over 50 years of aircraft maintenance of bonded structures, and I have seen thousands of injection repairs inmetal bonded structure that have resulted in bond failure in later service. Like you, my assertion was challenged by a senior technician, so I invited him to select a range of examples on scrap parts that we could destructively examine. Of 14 samples, every single injected "repair" was easily separated from the mating surfaces. I have also seen an example of a production injection repair to supposedly bond a rudder core to the trailing edge of the rudder mast. Remember that this component had zero hours when the repair was undertaken, so there is no chance of secondary contamination interfering with the bond, I was indirectly involved with the investigation after the rudder departed the aircraft in flight. The injection was in the region where the core was bonded to the mast, with that bond being the mechanism to transfer shear loads into the mast. However, because the bond was ineffective all of the shear loads were forced through the skin to mast fastened joint, and that caused a fatigue crack that eventually led to the fracture of the skin and failure of the rudder.

The reason that people blindly follow the mantra of undertaking injection repairs is that the process fills the air gap such that NDT can no longer find the defect. In reality, the process only HIDES the defect. Understand that adhesive bonding requires chemical reactions at the interface, and that requires that the surfaces are chemically active. In the case of production voids in either adhesive bonds or composite laminates, the resin systems have experienced a full cure cycle, so the residual reactivity will be negligible. The only exception may be in cases where the surfaces have been separated by actual fracture and then repaired before the surface oxidises of becomes contaminated.

Now unless the test coupon used to validate the repair process replicates the fully cured glossy surface typical of the interior of a void, the test is meaningless. Bonding to a surface with a peel ply removed will not replicate the true situation. I have yet to see any valid test results
that would convince me. I really don't care how widely used the process is. It is wrong. Remember, the world was told as absolute facts that the world was flat and all the planets revolved around the earth.

Regards

Max

You seem to be saying that resin can’t stick inside a crack or a void. If that was true composites and adhesives wouldn’t work in the first place.

He's saying that once the resin is cured - including the inside surface of a void which existed during curing - it is not very chemically active and is very difficult to bond to without significant prep, which you can't do to the inside of a void.

Much depends on loading, void sizes/locations/density, etc - but I think generally saying that post cure void filing treatments always result in full strength is a generalization that isn't well supported.

Are these injection repairs cured the same way? If autoclave is the desired approach, that doesn't sound like something that can be done on an operational aircraft

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I don't know about resins, but there are some coating systems that have a limited time in which to add another coating layer. How do you access the void? Drill a hole?

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That is correct, once cross-linking stops new cross-linked bonds can no longer form so there is certainly a time window within which a full strength repair can be made.

Secondly, epoxies blush. Uncured amines remain on the surface. They form a greasy feeling layer that can make it difficult for subsequent bonds to be made. Mechanical prep is required to remove amine blush which is not possible to do with an injection repair.

Thanks, Tug...

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Quote (Swinny)

He's saying that once the resin is cured - including the inside surface of a void which existed during curing - it is not very chemically active and is very difficult to bond to without significant prep, which you can't do to the inside of a void.

Yes that seems to be the claim. The composites industry disagrees with his claim. Resin injection repair is routine, and provides experimentally proven restoration of strength. Does it provide 100% restoration? Probably not. But blakmax is saying it provides virtually no restoration of strength, and is merely snakeoil used to pass NDT. That’s a fairly bold claim.

Quote (TugboatEng)

Swinny, I read that the compressive strength of carbon fiber is quite low, maybe 10% of a UTS of 175ksi.

Tensile strength for raw carbon fiber of reasonable quality generally runs up to about 400ksi. When combined with a resin to form a composite, the tensile strength is of course reduced by the resin's contribution to the cross-sectional area.

The compressive strength of carbon fiber composites depend almost entirely on how they are processed. Tests by sailplane designer Jim Marske in the 1990s showed that hand-laid carbon tapes could achieve something like 40-60ksi. When heroic measures are taken to ensure fiber alignment, tows and tapes could sometimes achieve almost 90ksi.

The carbon fiber pultruded strips I use in the wing main spar flanges of my sailplane designs are good for about 320ksi in tension, 200ksi in compression. To get non-scary-looking wing deflections under maneuvering loads, I generally design to about 120ksi at ultimate load of 8g. Using the pultrusions allows for good strength values without going to heroics in terms of materials or processes.

provides experimentally proven restoration of strength
oh really? please provide specific references. and the SAMPLE paper listed above is for one very specific condition, with delams at a fastener hole (due to poor drilling) and the results are not representative of most "injection repair" cases (the paper tested clamped up double shear conditions which are also not representative of most aircraft joints, which are single shear) such as edge delaminations, voids between core and facesheets, etc.

i've been involved with many injection repair cases thru MRB and have even run some tests, and frankly there isn't much data (beyond some "service experience") to back up what most MRB organizations do (which is basically justified by "it now passes NDT").

Quote (SWComposite)

please provide specific references

You're in the industry. I'm sure you can find references. I'm not really interested in quibbling over double shear vs single shear test results.

I'm just curious as to why you and blakmax think resin injection is essentially worthless. It's an odd claim.

Tomth

I've been in the industry for longer than most but I have yet to see a VALID test result that shows that strength can be restored through a few drill holes. I have tons of evidence that the injection repair for bonded joints in metallic structure simply does not work. Since these bonds were performed on fully reacted epoxies, I fail to see how they can suddenly work on laminates. I will be very interested to see other reliable test results. Show me!

The only way injection repairs have a chance of forming bonds is if the injected adhesive has a strong acid-base reaction to break the surface tension of the resin in the void.

Regards

Blakmax

Quote (blakmax)

I will be very interested to see other reliable test results. Show me!

From the earlier link I provided, which was resin injection at holes:



In that instance the strength of the repaired specimins match the pristine specimins.

SW has said no no no, that test is irrelevant, because it's not a delamination failure.

So here's another link, on flexural delaminations, which when repaired have 93% strength compared to pristine specimins:

https://www.sciencedirect.com/science/article/abs/...

I'm sure you and SW will have your reasons why this test too is a load of rubbish, but honestly it's pretty hard to believe you when you're not providing any counter evidence. Since you're disagreeing with industry practice, how about you provide some test results which back up your theory that resin injection is of no use.

I commented earlier that the towards the right sides all of the specimens converge. You mentioned that the ultimate strength of the repaired specimens was better than damaged. Do we typically design around ultimate or yield strength?

Honestly, I don't think the chart is very clear. What is the failure criteria? The specimens seem to be yielding but never yield to a conclusion.

The green and blue curves are similar and are superior to the red curves.

The right hand side of the curve is not the "yield" point. They're all failed by that stage. Hence the convergence.

I don't know they all still appear to be at 93% of the ultimate strength.

Having read the attached link, I make the point that in both the bolt hole specimen and the ILS specimen in the reference work, there is no possibility of a glossy surface such as would occur in production defects such as probably were referenced in the previous description of the post production defects. The bolt hole and ILS specimens the surfaces that would have been injected would have been induced by fracture of the resin system. Now, provided that the injection process was undertaken soon after the fracture occurred, there is a chance that the exposed surfaces would still be chemically active, so there is a chance that the surface would form a reasonably effective bond.

I would express an opinion that some caution must be taken in extrapolating those results to suggest that the repair method would still produce adequate results if the time after delamination was excessive, or if service conditions enable the possibility of contamination.

It is a very long bow to draw to suggest these results could justify injection of production voids.

Regards

Max

I was googling earlier to see if there were any actual factual updates on this (didn't see any), but did run across a Wikopedia article. Of interest in that article were a BUNCH of reference links, if anyone needs a few weeks' worth of reading.

Quote (TugboatEng)

Do we typically design around ultimate or yield strength?

Is this a serious question? Designing composite structures is not like designing with metals at all.

The "references" are almost all just news articles; the Wikipedia entry itself is almost shorter than its listing of "references"

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Welcome to the modern age where the factuality of an article is based on how many outlets carry it, even if the story is verbatim from each outlet and they all fire the same sources.

SwinnyGG, I asked a question.

TugboatEng

SwinnyGG's comments about yield/ultimate are correct, if a little blunt (a bit like my responses at times ). In general, composites are considered to be linear elastic to failure if loaded on the fibre direction, but there may be some features that resemble yielding but that is mainly due to resin deformation. The best design methodology is to design to a safety factor below linear limit. All of this changes with layup configurations; more fibres in the load direction or more resin dominated cross plies in the load direction; more shear loading or more axial loading.

But it is not as simple as that. As already discussed, the failure criteria for composite materials is Pandora's Box. The main issue is that failure can be by fibre fracture, fibre buckling, fibre shear as well as resin failure in tension, shear and compression. Then add in fibre disbonding from the resin.

Now I have criticised the Tsai-Hill and Tsai Wu criteria. The principle issue here is that this approach has evolved from the valid Hill failure criteria for ductile metals. This approach for composites is based on the STRESSES in each lamina. It is important to understand that the STRAINS between lamina must be consistent, but because of the different elastic moduli in the fibre direction and perpendicular to the fibre direction, the STRESSES are not consistent between layers. What is consistent between layers are STRAINS.


The issue with the Tsai-Hill and Tsai-Wu failure criteria is that the Hill failure criterion assumes a consistent failure mode (shear) irrespective of the loading regime. The principle criticism of Tsai-Hill and Tsai-Wu criteria is that the failure mode is NOT consistent for all loading regimes. In some cases, failure is by fibre fracture or fibre compression or buckling failure, or even shear failure. As with my discussion about stretching some successful injection repairs to boldly claim that ALL injection repairs are effective, then it is equally invalid to stretch the mathematical model from clear failure conditions to apply the mathematics to universal conditions. As I already pointed out the Tsai-Hill and Tsai-Wu criteria actually predicts a very significant INCREASE in STRENGTH under compression-compression strength as a result of changes in transverse TENSILE strength. I do not understand how a change in tensile allowables can generate an increase in compression strength. It is pure mathematical gymnastics, adn as I said, I hope it did not cause the loss of these lives.

There are strain based criteria (Hart-Smith advocated these).

The real trick with composite failure criteria is to match the failure mode with real test data, and I really acknowledge the excellent work that Mike Hinton et al did with ICCM to expose the reality in the deficiencies in this important aspect of composite technology. My understanding is that work by Jon Gosse (Boeing) actually provides a reasonable transition in failure modes under differing load regimes. But I have left that field of study years ago, so I urge readers to do their own research.

Hope this helps.

Max

Quote (TugboatEng)

SwinnyGG, I asked a question.

It is frequently not clear if you actually want information, or if you're trolilng.

So, ok. The answer at the 50,000 foot level is pretty easy. Generally, for composite structures, if the component has yielded it has failed. The plastic regime of the stress-strain curved is not used, in the sense that you factor ultimate design loads and in service load limits to stay completely out of the plastic regime in all but the most extreme outlier design cases.

So when you're evaluating that chart, you don't particularly care what happens after the peak of the curve, because when you use that criteria for design, you're staying completely to the left of the yield point on the curve. The peak value is what is important.

When you get into damage tolerance/load limits with various damage types/fatigue criteria it becomes very complicated and nuanced, but that's the executive summary.

Ok, to add to the above 2 excellent posts, for carbon fiber composites (fiberglass composites can be different):
- under in-plane loading (except as noted below), response is essentially linear to failure, so ultimate strength is used.
- for interlaminar failure modes, these are resin controlled, and often involve crack initiation and then growth, so in most cases the initial subcritical failure point is used (sometimes at limit loads and sometimes at ultimate loads, depending on application); also the maximum load is checked against ultimate loads. And in some rare cases people go down the deep dark path of trying to predict crack growth.
- for fastener bearing loads, the response is like shown in the plot above, assuming the critical failure mode is “bearing” and not shear out, cleavage or net tension which are linear to failure. For bearing failure mode, while the response shows “yielding” it is really a local crushing failure. For bearing strength a number of approaches are used. Maximum load is used at ultimate load. 2% Offset load is used at limit load as a quasi yield check. Onset of nonlinearity is used at fatigue load levels to (hopefully) ensure no bearing hole elongation under fatigue.
- there are a few other failure mode types that occur occasionally.
- and then once damage is introduced, residual strength analysis is complicated.

"The 'references' are almost all just news articles..."
Well yes, I didn't say this was a secret trove of unreleased knowledge, in fact, the opposite.
But virtually the entire discussion above and in the previous thread is based on (1) news articles (2) Oceangate's own videos (3) Youtube or magazine interviews with people not directly involved in the project, or (4) Speculation based on (1)(2) and (3). But those references are just putting a lot of this into one list.

SWcomposites, I remember detailing a fabricated steel beam and digging thru my omer blodget book and my structures book to find the shear at the web/flange transition, checked it twice and was like, Oh, I'm not going to get a welder to lay down that little metal, am I, and spec'd out 2" in 6 or whatever I had in the rest of the weldment. This becomes completely different if you only have resin transmitting the shear, doesn't it? So would a thick 0° layup have an intraliminar shear failure instead of fibre pullout or fracture when bent?

moon - possibly, depends on the specific loading, boundary conditions, etc. A short beam loaded in 3 point bending is used to drive an interlaminar shear failure to get that strength property.

SWC, Does the radial force gradient cause any trouble with a high pressure vessel like that? You have 5ksi radial at the outer surface and practically nothing at the interior surface.

"trouble"? hmm, actually, assuming uniform loading (eg, ignoring the end condition stresses for which we don't have enough design details to sort out, but were likely a complicated 3D stress state), then no the pure radial compression stress is not likely a problem. Thru thickness compression strength of carbon/epoxy laminates is ~ 20-25 ksi (tension is much lower).

BUT, this kind of thing would require a very detailed stress analysis of the assembly, and a lot of testing (which Oceangate seems to have not bothered to do). With composites one has to pay attention to stress concentrations, as there is no "yielding" as with metals to save one from design sins. And the apparent presence of fabrication defects complicates things further.

Decades ago I worked a project involving an underwater pressure vessel, for a military application, but the depths were a lot less than the Oceangate submersible, and I (vaguely) recall there were a lot of issues with the end domes and connections to the cylinder sections. However I wouldn't consider myself to have anywhere near sufficient experience to design a composite pressure vessel for the Titanic depths without a lot of fabrication trials and full scale testing; its a completely different loading condition and environment from that which almost all composites people are familiar with.

As far as I can tell, the hull with the noted defects was replaced.

Not a structural engr here, but I have put a fair amount of thought into this.

Some here seem to have a LOT of experience in structural composites, and I certainly respect that knowledge.

But to this generalist, I came up with a few possibilities:

1. Non uniform distribution of stress in the thick casting in compression. Progressive damage with each dive.

2. Water leakage or adhesive extrusion into edge of cylinder where the end caps engaged. Water or adhesive could extrude into the raw edge of the cylinder.

3. Simple osmosis. Water under that pressure will try (and may) ooze through the surface of the cylinder, getting between windings and weakening them.

4 Portal window blew in.

5. No apparent NDT, either pre or post dive, nothing to quantify progressive damage.




But the biggest gripe I have as a non-expert is the lack of testing. You can build something and not fully understand it. I have done so, quite a few times. But I knew what I knew, and I knew there were things I did not know.

What I did was test. Things failed that I sorta expected (cost factors), things I thought were solid failed or wore. Things I thought were iffy held up like champs. Designs were tuned based on the test results.

But I tested the prototypes and tested them hard.

OG did not seem to have any sort of rigorous test protocol. If there is a big enough hyperbaric water tank test rig, they could have put it there and cycled the pressure. Hundreds of times relatively quickly. Do some NDT after so many "dives" (pressure cycles).

If no tank available, the hire a ship and go north of Puerto Rico and repeatedly dunk the thing. 20k ft depth there. Again, NDT every so many cycles.

Last dive, lower to calculated crush depth and see if your modeling is close.

Quote:

OG did not seem to have any sort of rigorous test protocol.

THAT wasn't the issue; Rush didn't want a testing protocol at all, since that would effectively affirm that the naysayers were right and that testing was required to certify safety.

Whatever engineering sense Rush might have, or could have, had was completely subsumed by his, now obviously wrong, ideology that the certification process "stifled innovation."

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My feeling is that when innovation runs up against something like a "certification process", there is generally a good reason.
There are exceptions, but it takes a lot of testing to prove the exceptions.
Advice to the younger engineers:
If you think that the codes or testing protocols are wrong, it may it is often an indication that;
"You don't know what you don't know."
I think it was not knowing what he didn't know that did in Rush.

--------------------
Ohm's law
Not just a good idea;
It's the LAW!

"You can build something and not fully understand it..."

To add to this, you can have all sorts of designs based on over-simplified modeling, theoretical modeling without testing, etc.
But there are a couple of issues.
One is, "If in doubt, make it stout", and you can intentionally overdesign to partly allow for potential inaccuracies in the design process. The problem is, when you're trying to skim every last ounce off so the thing will float, this idea sort of defeats the purpose.
One is, consider the consequences. If it costs $200 to properly analyze a part, but only $50 to make it, and the only consequence of failure is to have to make a new one, then yes, take the shortcut and you're likely good. But if the consequence is "Instant gruesome death for all concerned", by golly, that's not the time for any shortcuts, either.

Quote:

I think it was not knowing what he didn't know that did in Rush.

He really didn't have to know much; his whole contention rested on the fact that almost all accidents were the result of operator error, but he only needed to think about WHY that was. If all were due to operator error, then the testing/certification was what got us to that point; while correlation is not necessarily causation, it's certainly something that has to be considered, even if you know nothing about the testing/certification.

I don't know much about the testing/certification, but I certainly recognize that it's at worst overly stringent by some statistical factor, so at best I could hope for is to nudge that factor down, not ignore it altogether.

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And bear in mind that testing to failure is expensive; Rush would have had to build at least 3 additional hulls to gain even a modicum of confidence in the results; if they failed, then it would have been even more expensive, since that would entail redesign, and even more testing. He saw that extra cost as unnecessary, since that's a cost barrier to entry, but he saw that as a form of stifling competition, and not as being prudent.

As engineers, we have to constantly question our motives and assumptions, because those, and just plain bad engineering, are what gets us into trouble.

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https://www.cnn.com/2023/10/10/us/titan-submersibl...

I guess the remaining debris has been recovered, with additional human remains.

Official press release for the latest debris recovery:

U.S. Coast Guard recovers remaining evidence from Titan submersible

USCG announcement of international agency meeting. The date for the public hearing is still TBD.

Coast-guard-interagency-and-international-partners-conduct-titan-evidence-review

It's been awhile, but this item just popped-up:

'What Could Go Wrong?': Audio Shows OceanGate CEO Joke Before Titan Sub Implosion

A resurfaced clip features the deep sea exploration company's co-founder, who died along with four others as they sought to visit the Titanic wreck.

https://www.huffpost.com/entry/what-could-go-wrong...

An excerpt from the above item:

OceanGate CEO and co-founder Stockton Rush joked “what could go wrong” months ahead of the deadly Titan submersible implosion last year, according to a newly-resurfaced audio clip from a documentary on the disaster.

The clip –– shared by the New York Post –– comes from an April 2023 radio interview about the mission to the Titanic wreck, just two months before Rush along with four others died in the disaster.

John R. Baker, P.E. (ret)
Irvine, CA
Siemens PLM:

The secret of life is not finding someone to live with
It's finding someone you can't live without

Yes, they showed this in the British Channel 5 documentary, “Minute by Minute: The Titan Sub Disaster documentary that aired last night and tonight. I spent too much time last night trying to find apps on my TV like BritBox that would play Channel 5, as it is impossible to get outside of UK without an app, but you have to pay for all these apps. IF anyone can find a link to this documentary online, let u know.

It appears to be available on their website. Might need VPN.

https://www.channel5.com/show/the-titan-sub-disast... I've tried to play it, but it just spins, so not clear who's at fault.

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Just watched this and didn't add much more knowledge apart from one thing.

I looked up more information on Hamish Harding and it turned out I knew him 35 yyrs ago when at 24, he flew 5 of us in a small twin engined plane into what was then semi communist Poland to jump out of various flying machines, mainly helicopters, but also fast jets, gliders and hot air balloons. Lost touch with him a couple of years later. Amazing to realise that.

Has they been any further official reports?

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Also: If you get a response it's polite to respond to it.

https://www.foxbusiness.com/lifestyle/ohio-billion...

"They did it wrong, I'll do it better." Hubris is never the way to start a venture. Hopefully, this one will be properly constructed and TESTED before anybody takes it for a ride.

I'd hesitate to pass judgement on Larry Connor's effort.

He's completed 3 dives to the Marianas Trench, and is paying an industry leader to build, test, and certify the sub (Triton).

He's going about it the right way, at least up to this point. He's not claiming to be a genius engineer that can do it better than everyone else the way Rush did.

Nice glossy website alright. https://tritonsubs.com/subs/gullwing/

acrylic globe!

not much about certification other than it is "commercially certified" whatever that means...

apparently they "intend" to have it classified by an external body.

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All Triton submersibles to this point have been certified by DNV. Including their 36000/2 model which is certified by DNV for operation at full ocean depth, was used to complete the 5 Deeps expedition without incident, has taken people to Challenger Deep multiple times, etc.

I get that because of Stockton Rush there is skepticism surrounding 'billionaire wants to build sub for titanic' but Triton is a legitimate company that is highly successful and has been building commercials submarines for like 25 years.

Rush's approach and what Larry Connor says he's going to do are apples and oranges.

The first comment sums it up, "My prediction: The Titanic isn't done claiming the lives of rich people who should know better."

-----*****-----
So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik

Let's face they still get in helicopters.

Riding a sub will be the billionaire's new Everest. I think it is time for an Onion article.

https://www.theonion.com/world-populace-actually-f...

Triton is quite literally in a different class than Oceangate, that's all that needs to be said.

Since the vehicle is seen only in computer renderings thus far, I had wondered if anyone actually intended to place an order for one.... I suppose we now know.

The idea of that giant acrylic bubble standing in for Alvin's no-expense spared titanium sphere with its small viewports is quite astonishing and I would love to know what just that component alone cost to build and certify.

Good to see some activity on this thread.

I thought of lighting a candle. Then a puff of air blew the idea out of my head.

I've seen a few articles about how he wants to prove the Titanic can be explored safely in a manned sub. Well, it's already been done many, many times so there is not much to prove.

latest article describing what a cluster this thing was: https://www.wired.com/story/titan-submersible-disa...

SWC - A great article - thanks for posting it. The skull and cross bones on the graph sent by the boeing engineer was an incredible find.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

An eerie detail - when Rush was operating a steel hulled sub and got lost, how did he expect an iPhone compass application to help? Steel won't completely screen out the Earth's magnetic field, but it is so easy to magnetize regions in the steel that careful calibration to compensate is required. How did he know so little about materials?

Rush was an arrogant fool with just a bit too much money, and just a tiny bit of knowledge, all of which made him very dangerous. I'm just happy that he was onboard the Titan sub when it imploded, because otherwise he would have blamed (and probably sued) everyone but himself for the catastrophe.

What a depressing story; it's so sad that he took the lives of 4 innocent people with him.

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A Forensic Analysis of the Titan Submersible Implosion | Webinar https://365.sampe.org/events/91134

Whatever the analysis states, the only part of the sub we have seen are the titanium domes. There was ZERO adhesive attached to the domes which means the failure occurred between the adhesive and the titanium. We all saw the video of the gluing process, the surface was not grit blasted immediately before assembly and it was not primed. They were also touching the surface with their bare hands.

I have not seen any of these observations made anywhere.

Quote (TugboatEng)

We all saw the video of the gluing process, the surface was not grit blasted immediately before assembly and it was not primed.

The Wired article contained another revelation about this, that the titanium domes and interface rings were not new to the second (disaster) hull, they were the same ones used with the first hull (the one from the gluing video?) How were they removed and how were the surfaces prepped?

The article also notes that lifting points were added to titanium segments, and that such loading was not a consideration in the original design.

I don't see those things as issues. The dome didn't fail so the lifting points didn't contribute and the face of the dome can be shaved to remove a few thousandth of an inch without compromising strength.

Quote:

The dome didn't fail so the lifting points didn't contribute and the face of the dome can be shaved to remove a few thousandth of an inch without compromising strength.

One cannot tell from long-distance photos whether the flanges/domes were, or were not, compromised by asymmetric lifting forces.

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The load at the lifting point will have pulled the dome into an egg shape in axial view which might compromise the bond between the dome and the tube. I doubt we'll ever know. Metal to composite bonds is one of the few areas I know enough to be dangerous in. Basically it is an impedance mismatch problem. If you imagine a metal plug in a tube, in side view you must taper the metal so that the stresses can gently build up in the tube.

From a very high level the 'system' worked. That is, he was told not to do things he proposed, he did them, and killed 4 other people. The rest of the industry has hence been reassured that the usual standards are useful, if not optimal.

Cheers

Greg Locock


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Oh dear:

Tugboat says: Whatever the analysis states, the only part of the sub we have seen are the titanium domes. There was ZERO adhesive attached to the domes which means the failure occurred between the adhesive and the titanium. We all saw the video of the gluing process, the surface was not grit blasted immediately before assembly and it was not primed. They were also touching the surface with their bare hands.

I implore people to understand that adhesive bonding is a chemical process. Bond strength AND longevity depends totally on the chemical bonds (mainly covalent) that are formed that the interface at the time the bond is formed. THERE IS NO MAGIC PRIMER OR ADHESIVE. Every part of the process requires that the process addresses three things:
1. The surface must be clean and free of contaminants that will inhibit the formation of chemical bonds. Please do not use detergents because surfactants wet the surface well enough to displace the contaminants but they leave a leyer of well attached detergent that prevents adequate reaction.
2. The surface must be chemically active. It is no use applying a primer to a fully oxidised surface. You must remove the exisiting oxide layer.
3. you must IMMEDIATELY apply a primer to stabilise the surface. Of fundamental importance that the primer develops a chemical structure that is resistant to hydration. The most common form of bond failure is because the surface of the metal hydrates, for example titanium oxides hydrate to form hydrated oxides and in the process the chemical bonds between the oxides formed during original bonding processes dissociate leading to interfacial failure. The resulting separation at the surface will exhibit a total absence of adhesive, as described above by Tugboat.

The process described by Tugboat clearly does not sound like a process that would meet any of the basic essentials to produce an adhesive bond that would provide bond durability under severe exposure to a marine environment under pressure.

So sad.

Blakmax

The process my partner in crime developed was an ultrasonic bath in MEK, grit blast, prime, and glue. I may have the order of the first two wrong.

Cheers

Greg Locock


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The OSHA whistleblower got sued and had to sign an NDA?? Either there's more to that angle, or whistleblower protections don't seem to be worth much . . .

The NDA was part of his employment contract

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Blakmax, I am aware of the electron sharing that occurs as materials are bonded. My emphasis is that titanium readily oxidizes in air. That is what gives it it's corrosion resistance. Tbe trouble is that the electrons in titanium oxide would prefer to exchange with water instead of the amides in your typical epoxy. Hydration, the formation of titanium hydrate from exposing titanium oxide to water robs the electrons from the epoxy bond weakening it. I believe this is what has happened in this case from the evidence that I have seen.

Siloxanes are a recent development that are being used to prime surfaces and prevent hydration. I am not an expert on this subject but am very curious about it.

Tugboat

You are exactly like you say. The same oxidisation occurs with aluminium, where this is the exact mechanism that causes interfacial (adhesion) failure in aviation structures. We have experience with epoxy silanes to prevent hydration on aluminium surfaces with very significant results. We have treated titanium alloys with a significant improvement in results, but not to the same extent as for aluminium. The product we use is Dow Corning Z6040, but I would also try a product marketed as Boejel also sold as A C130 in kits. The best test is ASTM D3762 wedge te4st, but due to a stuff up, the upgraded version of the standard did not make it before the cut-off date so ASTM deleted the standard. If you contact me I may put you in the right direction.

Max

Adhesion Associates

Wonder what the substance of the whistleblower complaint was? I believe if NDAs can be enforced to leverage coverups of (engineering) safety problems by suppressing whistleblower reports that is a high priority problem needing a solution. But maybe it's just vague reporting of that detail and the complaint and law suit were coincidental rather than related.

I think the problem was that there was no AHJ in international waters and hence no body to blow the whistle to. If it was to OSHA, did they in fact have jurisdiction?

The information I think was being made available to the deep submersible "community" in the hope that peer pressure would bring Rush to his senses.

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Also: If you get a response it's polite to respond to it.

Quote (LittleInch)

I think the problem was that there was no AHJ in international waters and hence no body to blow the whistle to.

Design/build/testing were all within the US or within territorial waters, i.e. OSHA regs apply

Fair enough - then it doesn't look like OSHAs policy was strong enough?

Remember - More details = better answers
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Or whomever showed up didn't understand what was going on

or they didn't show up prior to the sub entering service

I'm not super clear on the timeline of the OSHA complaint and what happened or didn't happen and when

This looks to be the best explaination.

Longridge basically got bullied into submission with the threat and actualisation of law suits which he realised would make him bankrupt and destroy his life, even with the theoretical protection of whistleblower legislation.

https://www.thedailybeast.com/how-a-bogus-lawsuit-...

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

I don't think OSHA cares until there are actual employees being endangered.
I can sit here and design Mars spaceships with a factor of safety of 1.001, and that is not an OSHA concern at all.

OSHA was involved for the anti-whistleblowing actions ; that retaliation is an endangerment to the employee in particular and all other employees who would hesitate to speak up.

Thanks LittleInch. The conclusion "This tragedy should serve as a wakeup call to state legislatures and Congress alike that they must do more, and soon, to prevent powerful interests from silencing speech they find inconvenient, uncomfortable, or embarrassing through abuse of the legal system." seems well-supported IMO, though expectation much notice will be taken less so.

It's hard to act ethically as an engineer when neither the authorities (or the court of public opinion) seem to have your back.

I haven't been following, so if this is already mentioned, sorry.

Was this the first dive the Titan took to the Titanic wreck, or was it the first dive of substantial depth? If I knew this at some point I've since forgotten. What was the maximum depth this unclassified submersible achieved and returned to atmospheric pressure without rupturing?

I believe they had completed a few successful dives, already with the Titan.

Yeah, LittleInch, the fellow was also "here on the visa from his employer" so it started from a highly awkward situation for the employee. Forget it, Jake, it's Chinatown. Keep in mind the vast numbers of similar visa from the employer folks are in Redmond, WA, and San Jose, CA, for example. Although they aren't likely to get into an OSHA tangle, they are not in a fantastic legal situation to be a whistleblower, similar to that guy.

The bit about "no jurisdiction," there's at least something to that, the thing only operated in international waters, the "passengers" were "crew members", etc. etc. etc. there was a lot going on and lot of nuance as well.

It looks like my question has been answered, there were quite a few dives, the vast majority weren't to that depth. 13 of 90 did not reach the target depth.

Titan sub only reached the depth of the Titanic on 13 out of 90 dives, says the waiver OceanGate passengers had to sign, Jyoti Mann, BusinessInsider.com, July 9, 2023, accessed 6/21/2024.

The OSHA regulations for the construction of the sub would apply to the workers on the site in the building performing any work on the site, it has nothing to do with the safety of the submersible. OSHA regulations apply to workplaces, so and Amazon warehouse, sure, but the regulations do not apply to the contents of the warehouses, because they aren't people.

OSHA regulates the usage of vehicles by employees in the workplace; the Titan was operated by an employee in its usual workplace, ergo, the safety of the Titan should have been under the purview of OSHA

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Does that mean OSHA should have chimed in on the Columbia and Challenger shuttle failures?

Astronauts were not paying customers.

I'm not aware that OSHA regulates employee safety in international waters, though.

If the US has jurisdiction, either through the flag of the mothership or the company operating the sub (or while they are still within 12/24 miles of shore), I believe it falls under the USCG. I believe the sub itself was registered in the Bahamas, to further escape regulation. In the case of the loss of the Titan, the mothership was flying a Canadian flag and owned/operated (not sure of the exact details from memory) by one of the Canadian First Nations.

It's a complicated situation for jurisdiction. Canada seemed to be quite happy to let USCG take the lead on it, which makes sense in terms of the relative resources available. As with aviation, it's normal for multiple nations to have an interest, and they are used to working together on the investigation.

SOLAS is the international safety at sea organization but not all vessels are subject to SOLAS rules. None of my vessels are.

Quote (3DDave)

Does that mean OSHA should have chimed in on the Columbia and Challenger shuttle failures?

.......they did. Astronauts are full time employees and are subject to OSHA regulated conditions. There was even a special ruling concerning astronaut radiation exposure while in flight at high elevations in the 80s that still carries the force of law today.

Quote (TugboatEng)

Astronauts were not paying customers.

OSHA doesn't regulate anything related to paying customers.

They chimed in on ionizing radiation for which NASA got a concession from them because no practical means exist to shield astronauts from ionizing radiation; instead they went to exposure limits.

AFAIK OSHA did not issue any recommendations about solid booster o-ring seals or the ability of ice to damage carbon-carbon heat resistant tiles or the lack of emergency exits or any of the other typical adaptations OSHA requires for dangerous work.

OSHA does not have jurisdiction over federal or state employees, states have the option of creating their own OSHA approved state offices like cal osha. I haven't had the benefit of a osha regulated workplace in 20 years.

Actually, I was googling that very question, and it looks like OSHA rules do apply to federal employees as of 1980 (but not state or local) although OSHA's enforcement authority is curbed in those cases.

A little off topic but I think people should know this. State employees can opt out of social security as well.

Quote (3DDave)

AFAIK OSHA did not issue any recommendations about solid booster o-ring seals or the ability of ice to damage carbon-carbon heat resistant tiles or the lack of emergency exits or any of the other typical adaptations OSHA requires for dangerous work.

They didn't have much to say, considering that astronauts are subject to a lot of hazards with no realistic possible mitigation - but OSHA staff were part of both investigations and NASA files notifications to OSHA about employee injuries/fatalities just like the rest of us do.

We're sort of in the weeds here but... point is, the sub was designed, constructed, and tested on US territory. At least those portions of the process would have been subject to OSHA regulation. US employees working on a US designed platform that's deployed in international waters are outside of OSHA's jurisdiction for enforcement of workplace safety code, but not outside OSHA's jurisdiction of enforcement for whistleblower protection.

It's possible OSHA may have seen a whistleblower complaint concerning the sub and ruled 'it's deployed in international waters, nothing we can do' or something to that effect

OSHA reports they have jurisdiction to investigate complaints of retaliation against employees under 25 different statutes.
To the extent Lochridge could be considered a "seaman", the SPA prohibits retaliation resulting from "the seaman has refused to perform duties ordered by the seaman's employer because the seaman has a reasonable apprehension or expectation that performing such duties would result in serious injury to the seaman, or other seamen, or the public."
Or it might be one of the other 2 dozen statutes.
For all the good it did in this case.

Definitive investigation under way.

https://www.bbc.co.uk/news/articles/cx2kk1g66n7o

Looks like they had some sort of notice as they said they had dropped two weights, but didn't get very far.

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Also: If you get a response it's polite to respond to it.

There's apparently a flurry of new USCG activity in the investigation
https://www.news.uscg.mil/News-by-Region/Headquart...

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Pilot/ex-DoO/whistleblower Lochridge is telling his side publicly to the USCG: https://www.nytimes.com/2024/09/17/us/titan-submer...

There's a lot of interesting newly released info at the link from IRstuff
https://www.news.uscg.mil/News-by-Region/Headquart...

1. Preliminary design report for the carbon fibre sub completed by Boeing (2013)
- Suggests that it is feasible but acknowledges some of the risks inherent in CFRP and challenges due to differential thermal expansion, imperfections in the CFRP, and need for NDE. Suggests a need for further analysis.

2. Design report by the president of Spencer Composites (June 2015)
- Does not appear to give any consideration to the effects of imperfections on the design or any mention of a need for NDE.
- Claims that the design meets ASME BPVC Sec VIII Div 3 requirements.
- Suggests that either a titanium or composite dome could be used.

3. Stakeholder update by Stockton Rush (December 2015)
- The composite domes on the 1/3 scale model failed far below the predicted pressure.
- Claims that "Boeing with all their supercomputer capacity admitted they were unable to analyze such a structure" - Boeing's report didn't say that, but it did mention that "Compound curvatures such as spheres or ellipsoids generate additional discontinuities due to converging or diverging discrete material product forms which create gaps and/or overlaps between adjacent tows of slit tape composite material. These discontinuities can create local stress variations [which] reduce the capability of the structure. In general, composites are very efficient for in-plane loads, but complex loading near hardpoints or load transitions require cautious analysis for pristine and flawed structure. For this reason a hybrid concept was adopted..."
- OceanGate had apparently relied on the Spencer analysis for the composite domes. This analysis did not appear to include "cautious analysis for pristine and flawed structure" - it appeared to assume it was pristine with no gaps, delamination, or overlap.
- States "it is believed that the hemisphere buckled which was the reason our strain gauges did not give us warning of the failure. For the next test we will include acoustic monitoring which should give a better warning of this type of failure."
- Does not appear to recognize that they should not depend on analysis that significantly overestimates pressure at buckling failure (possibly because it did not consider imperfections).
- Also does not appear to recognize that buckling happens very quickly, so acoustic monitoring will likely result in an alarm sounding too late.

4. Quality Inspection Report by David Lochridge (2018)
- Very many significant problems, from those that should be easily avoidable (flammable flooring and internal materials that emit highly toxic gases upon ignition) to fundamental problems (visible significant delamination and porosity in the hull with no NDE to quantify the extent of the defects).

5. Risk Assessment for the ill-fated expedition (2023)
- Did not seem to consider any need for verification of the hull pressure integrity or inspection to find defects well before they led to failure. The only relevant item mentioned is "Monitor Acoustic Emissions system for extra ordinary acoustic hull events" as a "Control Measure" for the "Confined space" hazard during the dive.
- Note that there are items related to the "Pressure energy" hazard of the high-pressure air and low-pressure air systems, including inspecting for wear and damage, but they did not give the same consideration to the pressure vessel that would contain human occupants.
- Relies on the oft-criticized "severity x likelihood = risk" formula, with 5 levels with defined criteria for both of them
- Hazards do not seem to be well-defined
- Looks like somebody just assigned the severity and likelihood numbers based on intuition (and possibly avoiding any "High" risk ratings)
- Highest determined risk is 10 [Medium] - maximum possible on the scale is 25.

So far no design analysis performed after June 2015 has been released. I think the June 2023 failure was on a hull built by another manufacturer after there were some significant issues with the Spencer hull, but they reused the end rings, so they might have continued to rely on the same design analysis.

Thanks jmec87.

I quickly scanned the Boeing and Spencer reports.

As a former Boeing composites engineer, I'm not impressed by the Boeing report, even for a quick feasibility study.

The Spencer report is troubling. This statement "Defining the ultimate allowable for flexure as 85% of the mean as before results in an allowable strain of 12010. It is probably realistic to use this allowable where high strain is isolated and surrounded by lower strain material" is just IMO insane, as designing to that level of strain is just crazy. And it appears that most of the material design properties are based on assumptions and limited data. Such as:

"A compressive strain database is not available and a design allowable was derived based on available data in Mil-HDBK-17 (Ref. 2). This data is for ~34 msi carbon fiber/epoxy, for eleven fiber/resin systems. The compressive stress data for these eleven unidirectional laminate types were combined into a single data base consisting of 323 total test specimens with a mean compressive strength of 214 ksi (normalized to 60% fiber volume). The data in Mil-HDBK-17 is pre-1990. Fiber tensile strength for 37-800 has increased by more than 20% over the fibers used at that time, so it was assumed that the mean unidirectional compressive strength for 37-800 is at least 1.15x214 ksi = 246 ksi (60% fiber volume). The design allowable was defined as 85% of this mean value = 209 ksi. The compressive strain allowable corresponding to this stress in a unidirectional 37-800 laminate is 9400." This is just rubbish. Assuming compressive strength increases when fiber tensile strength increases is just wrong.

I'm not going to comment on the FEM analysis, other than to say the meshing looks terrible in some locations.

From the Quality Inspection report, showing the hull laminate "quality":



Just horrible.

LittleInch's post 17 Sep 24 07:37 woulda been a great time to start Part 3 :)

The problem with sloppy work is that the supply FAR EXCEEDS the demand

Quote:

From the Quality Inspection report, showing the hull laminate "quality":

Surely this picture is a joke???

----------------------------------------------------------------------

Why yes, I do in fact have no idea what I'm talking about

Quote (Just Some Nerd (Structural))

Surely this picture is a joke???

David Lochridge (OG's former Director of Operations and author of the notorious inspection report of Titan that got him sacked) discussed this photo as it pertains to his report during today's board hearing, it's at the 1:50:37 mark of the video:

https://www.youtube.com/live/SNrs8VA963w?si=PbwNbL...

Yesterday's testimonies from Tony Nissen (former Director of Eng.) and Tym Catterson (contractor, experienced sub pilot, was topside on Polar Prince during the disaster), and today's from Lochridge are well worth listening to in full for anyone interested in this case. The sessions are 7-8 hours but I wait until after the live feed ends, speed up the video to 2x and skip through the breaks which reduces it to 2-3 hours.

From this article, it appears that the weights could have been dropped to minimize the impact with the ocean floor, not because they were trying to return to the surface.

Quote (ABC NEWS)

Tym Catterson, a former contractor for OceanGate, testified during Monday's hearing that there were "no red flags" on the day of the incident. He said he believes the intention of shedding the two 35-pound weights was to slow the vessel down as it approached the ocean floor. He thought the weight was dropped a little early than is typical -- not due to any emergency but to ensure a smooth landing, he said.

"Considering who was in the cab with Stockton at that particular time -- there are two billionaires in there with him -- I would absolutely guarantee that he's trying to make sure that this just goes as absolutely perfect and spot-on as he can," Catterson said.

https://abcnews.go.com/US/titan-submersible-implos...


Also that pic of the hull material looks like the stuff they use to protect loading docks from truck impacts.

The only part of the sub that we have seen post failure is one of the titanium domes. There was zero carbon fiber attached to it. I read that as the bond between the carbon tube and the titanium dome failing. Remember, this sub had made 13? dives to full depth. Is carbon fiber laminate so sensitive to fatigue? Meanwhile, metal to epoxy bonds are very sensitive to degradation from water exposure.

TugboatEng,

One of the reasons for using titanium is that it is chemically very stable. How well do adhesives stick to it?

--
JHG

The issue that most people have noted and also brought up again recently is that the record of the vessel actually works against it.

So saying it's ok, it's been to depth 13 times already, is actually a bad thing. Any failure of a fibre is non repairing and hence every dive probably lobbed a few percent off its capacity to resist external pressure, which wasn't much above 1 anyway. So in this case sooner rather than later they just ran out of life. Not really fatigue, but more operating far too close to the margin and not having any way to NDT the vessel after each dive. Or indeed NDT it to start with.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

Quote (drawoh)

....titanium is that it is chemically very stable. How well do adhesives stick to it?

Bonding titanium components is not ground breaking - it's very common in certain parts of the aerospace world - but getting a high quality, high strength adhesive bond to titanium parts is still a non-trivial process. You can't just buy a product off the shelf and slather it on and get good results. Similar to adhesive bonding of stainless steels and to a lesser degree certain aluminum alloys, material types/surface cleanliness/surface preparation by chemical or mechanical means are very critical. To design a process for a bonded titanium component with a service depth of 4,000m, you'd need to invest serious time and capital into a true bonding engineering design. Which it doesn't seem oceangate ever did. And based on the videos of them setting the ring and hull joints, they don't appear to have been following any sort of meticulous or detailed process controls.

Just thinking out loud here, but I wonder if Rush got the thought in his head that because these adhesive joints were always in compression in service, investing the time to develop and fully understand the bonding process between those components was not necessary. That obviously isn't the case.

"but I wonder if Rush got the thought in his head that because these adhesive joints were always in compression in service, investing the time to develop and fully understand the bonding process between those components was not necessary."
Well, that thought certainly entered my head, but then again, I'm not building my own submarine, either.
I'm not aware that you COULD bond carbon-fiber edgewise to a ring of metal and develop anything like the strength of the carbon fibers. If the glue was that strong, you wouldn't need the carbon fibers.
But one reason for thinking this joint was not so critical- if I recall correctly, on the old bathyspheres, they were actually forged in two or three pieces, then simply slapped together with no weld or glue. Of course, that was a spherical shell, which theoretically had no bending. Attaching metal hemispheres to a plastic cylinder, you'd get shear forces and bending moments at that joint, but it still seems very reasonable that the compressive stress and resulting shear friction could very well be higher than the bending or the developed shear at the joint. At any rate, I don't remember anyone claiming that was what failed, but rather just the cylinder itself.

Video of the carbon fiber wreckage and domes on the seafloor has been released:

https://www.youtube.com/watch?v=eEThkm0Dih8

Drawoh, titanium, aluminum, and stainless steel all have a similar challenge when the bond is going to be exposed to a wet environment. All of the metals rapidly form a thin oxide layer on their surface in air. Adhering to this oxide layer is problematic because the electrons in the bond have a higher affinity for water than the epoxy. The metal oxides form hydrated and the bone is lost. We've all seen the way paint flakes off aluminum in large chunks.

In the advertising videos they show the joint being bonded. The joint is as machined. I assume there was some time elapsed between machining and assembly which means oxides are present. The joint should have been abrasive blasted immediately before bonding. If that is not possible there are primers available to extend the time between blasting and bonding. Silane based primers are the cutting edge.

I've just watched the video and it's notable to see that nearly all of the craft is packed into the forward done and the hinged connection on the forward dome is blown open. This makes me think that the connection at the rear dome failed first which cause everything to get pushed forward into the forward dome.

Quote (JStephen)

if I recall correctly, on the old bathyspheres, they were actually forged in two or three pieces, then simply slapped together with no weld or glue

I have my doubts about that.. you would need to hold them together somehow. The first bathysphere ever constructed was a 1" thick steel casting, 5' diameter and cast in one piece.

Even if the 'bathyspheres were multiple pieces with no seals between' thing is true, there's one factor that would aid that approach, which didn't aid Titan; two halves of a sphere made from the same material would have the same stiffness in response to service pressure, and would have the same expansion and contraction rate when undergoing temperature changes.

Titan's hull was made from multiple materials and assembled at or near room temperature. For metal parts that big, 40 degree negative delta at the service depth would cause non-trivial dimensional changes, which would not be exactly matched by the CFRP tube. You're putting a fair amount of direct shear stress on that adhesive joint from the temperature change alone.

Metal scraping is a very old school technique that did enable gasketless flanges. I don't know if this applies to your comment but there are ways to assemble joints with no weld or glue but they are absolutely not slapped together. They may be lapped together.

Perhaps this video has already been posted - if so, sorry for the repeat.

https://youtu.be/ciZHwe-9ago?si=KFDswnhbm-xjPpaG

Ignoring what is alluded to be a digi-creation voice for narration and some in-video ads, the presentation makes some interesting analysis of the design and CFR hull and its implementation and the preferred test regimen it should have been subjected to prior to use with human passengers.

Additionally, an analogy to TNT force is presented as many others on this thread have already provided and calculated. Seeing a visual representation really highlights the force and rapidity of the implosion.

Brian,

No there's a raft of videos coming out now which are very interesting.

From yours this is an interesting graph and his calcs basically show that their predicted collapse pressure new was about 56MPa, with a dive depth of 4000m (40 Mpa). So at best a FOS from operating to COLLAPSE of 1.4. As the commentary says, this only works when you have full knowledge and reliability of the data used in the analysis.

Then as the number of deep dives increased that FOS reduced until it failed. But 1.4 FOS is absolutely nuts.



The second set of photos and analysis seems to indicate that the failure point was at the entrance end where the titanium ring met the CF hull and has been speculated on here previously as being a crucial and likely source of the failure point. The photo below shows the far end with all of the CF material basically compressed into the end shell. The other end cap and the dome blew out in the collapse.



Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

Littleinch - yes, the simulation appears to have chosen/calculated an initiation of implosion at the front dome interface. The actual evidence contradicts that mechanism. After seeing the photos of the actual debris site, I understand why no CFR hull components were present in the sea surface recovery photos - there is no hull remaining! The hull suffered a complete shattering. Quite sobering. I have to wonder if the lack of a precedent implosion wreckage of a CFR hull caused the OceanGate team (as guided by Stockton Rush) to underplay/downgrade the severity of an implosion event? Any engineering effort to develop a similar vessel will now have explicit evidence of the enormous risk involved.

Since the OceanGate team never sent an actual unmanned Titan to full Titanic depth until failure, each of the manned dives probably increased their confidence level with the hardware and caused a normalization of implosion risk. All the creaks and snaps of the hull became accepted - similar to the acceptance of the sounds of an old but trusted vintage automobile. Unfortunately, their risk analysis apparently discounted buckling failure is instantaneous and testing to failure with a full size vehicle would have provided much insight into the safety of the design.

That material that is sticking out of the front ring and dome looks to be where the high-pressure air cylinders were stored under the floor.

The testimony of Tym (forgot last name) indicates his belief that the hull was being squeezed in a way that local bending at the interface with the wring was being resisted by the tension in the adhesive, but that the adhesive was, dive after dive, coming loose circumfentially until it could no longer resist the shear load from the differential squeeze between the carbon fiber hull and the titanium ring, leaving only the small step in the ring. When it reached a point of critical damage the remaining adhesive failed, momentarily transferred the load to the small step, which he observed had been completely sheared, indicating an event so rapid the failure could not have started at one location and progressed.

He observed that at the rear the progressive shear of the ring was observed as a curlicue of metal that remained attached, indicating a secondary and slower failure.

This isn't an initial buckling failure, it appears that the diameter of the carbon fiber hull was being elastically squeezed to a smaller diameter than the elastic squeezing of the titanium end caps followed by the inability of the eventually unsupported open end of the tube to remain stable after the connection was sheared off.

3DDave - is Tym's testimony part of the MBI? So he is saying the failure was caused by the inner wall of the end ring that formed the engagement channel for the CFR tube sheared off (collapsing radially inward)? This would mean the predictive modeling did not account for a failure mode that is well understood. Cyclical stress to the titanium hoop of the engagement ring should have been seen. (I am assuming OG used an analysis program more involved than something like Solidworks Simulation or Autocad Inventor's built-in). Of course, the model may have been influenced by expectation of continuous adhesive bonding to provide control of the bending moments created at the engagement grooves of the end rings. But the fault analysis should have included evaluation of loss of adhesive bonding.

And the failure modes missed in the computer modeling would been more likely recognized if a full size vehicle had been tested to failure with repeated dives to Titanic depth.

Does the computer modeling account for hydration of the adhesive joint? We saw the assembly video. The joint was not properly prepared. The design may have been sound, all of the computer modeling may have confirmed this. It doesn't matter how strong the design is if you don't tighten the bolts.

Why did the USCG allow so much effort to be wasted on speculation and misdirected studies before releasing these images?

Why would / how could a computer model include that?

As to testing a full sized vehicle - they did, and it lasted for a largish number of cycles, n-1, as it turned out.

What they didn't do was perform any inspections of the joint to see if it remained OK. That testing could be done on a smaller sample that applied similar amount of tension and then put that under the same sort of pressure to simulate infiltration into the matrix. One can generate conditions more severe than a full size test in order to discover failure modes for the bond.

Certainly scale testing could have been done (and may have been done to some level) to develop guidance but I don't think OG had any feel for fatigue failure modes of the hull. Had they tested a full size hull to failure at Titanic depth, the n= 14 limit might have been recognized.

"Piccard's original pressure sphere was built by Acciaierie, Terni of steel forged in two hemispheres and welded to form a sphere 2.4 metres (7.9 ft) in diameter and 89 millimetres (3.5 in) thick,[7] This pressure sphere was replaced in December 1958 with another cast by the Krupp Steel Works[8] of Essen, Germany in three sections; an equatorial ring and two caps, which were finely machined and joined by the Ateliers de Constructions Mécaniques de Vevey. The new sphere was also steel, but smaller at 2.16 metres (7.1 ft) diameter and with thicker walls, at 127 millimetres (5.0 in),[5] calculated to withstand the 1,250 kilograms per square centimetre (123 MPa) pressure at the bottom of Challenger Deep plus a substantial factor of safety."

From: https://en.wikipedia.org/wiki/Trieste_(bathyscaphe)

And, quoth:
"On 15 November 1959, as the Trieste with Piccard and Project Nektron director Andreas B. “Andy” Rechnitzer on board completed a record dive of 18,150 feet, a glue joint on the bathyscaphe’s pressure sphere failed because of unequal expansion during the temperature change from the frigid depths to the tropical surface. Its center section was offset at one end by about 1/8-inch. The sphere's components needed to be realigned, rejoined, and resealed, but the mission's forward base at Guam did not have the necessary facilities."
From: https://www.usni.org/magazines/naval-history-magaz...

And again,
"A preliminary dive to 4,900 feet was satisfactory, but the next dive to 18,150 feet was marked by water leaking into the sphere. The sphere had been made in three parts, a center ring with a cap on each end. The joint between the parts was machined perfectly and then bonded together. Upon arrival at the surface, the epoxy bond was damaged, however, and emergency measures were employed in order to enable the project to continue safely. The three sections were held in place by steel bands, and a new sealing system was imposed on the joints. Several more test and practice dives were made, and the sphere was considered satisfactory. The next stop was the Challenger Deep."
https://www.usni.org/magazines/proceedings/1964/au...

So not "slapped" together, rather "machined perfectly and then glued together".

Scott Manley's video shows the other dome, with some hint of the window flange, so that should be the front dome.



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New documents have been added to the Marine Board of Investigation website, including a very interesting transcript of the meeting between David Lochridge, his boss, and Stockton Rush.
https://www.news.uscg.mil/News-by-Region/Headquart...

A few points:
1. Rush wouldn't even give Lochridge some of the certification / documentation that he did have, possibly because he thought they would have scared him even more than not being able to see them.
2. Rush claims emphatically that everybody else is wrong and carbon fibre is actually better in compression.
3. Rush is sure that he won't die on the sub because any failure will be gradual and he'll have enough time to surface before any implosion. Rush stated "It doesn't just implode. It screams like a mother before it implodes." He claims that other experts have also told him that he'll hear it before it fails.
4. Rush claims that "everything [the Spencer PhD engineer] has told us has been wrong", but he still insisted on using the hull designed and built by Spencer.
5. Rush admitted that he had no idea what depth the hull would actually be good for.
6. Rush doesn't seem to have given much consideration to the possibility of the bond between the hull and end caps failing, or that this would likely be a quick failure without much warning from the acoustic monitoring system (i.e. it probably won't "scream like a mother" before this type of catastrophic failure).
7. Rush seems to think that voids don't really matter and are unlikely to grow in a significant way because he has the right glue between the layers.
8. Rush doesn't value traditional NDE because he doesn't know what to do with the data. He thought the acoustic monitoring data would be useful for preventing failure, but as pointed out by Lochridge, Rush had no baseline for the acoustic monitoring data, and thus no way to tell if a sound means impending doom or is just a "whale fart". Rush claimed they hired a PhD in statistics to help them figure out the meaning of the sounds, but there doesn't seem to be any plan for this, and they won't know what sounds are indicative of failure until after a failure has occurred.

Admittedly I haven't been following all the docs super closely, but they didn't even take a replica to failure as some sort of baseline "training" of the acoustic monitoring program that they were basically swearing to?

Quote:

Admittedly I haven't been following all the docs super closely, but they didn't even take a replica to failure as some sort of baseline "training" of the acoustic monitoring program that they were basically swearing to?

Rush believed that testing to failure was detrimental to the advancement of the state of the art, i.e., the rigorousness of testing prevented innovation.

Obviously, he was an idiot in that regard, and killed 4 other people in his insanity.

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Quote (TUGBOAT)

Does the computer modeling account for hydration of the adhesive joint?

Quote (3DDave)

Why would / how could a computer model include that?

Tugboat, it is not possible to model interfacial degradation due to hydration.

3DDave. The reason for addressing hydration is that it results in one of the most common forms of bond failure.

ALL adhesive bond design methods inherently assume that the bond is sound and the processes are reliable enough to prevent hydration. This assumption is further weakened by a widespread belief as proposed elsewhere here, that demonstration of strength by testing of samples or full scale tests will provide assurance of ongoing structural integrity. If a surface that is susceptible to hydration driven interfacial failure (adhesion failure) any demonstration of strength will only assure structural integrity at that given time. It will NOT guarantee future strength because hydration is dependent on TIME since manufacture, as well as secondary factors such as exposure to water, temperature and possibly even exposure pressures.

The best way to manage this form of failure is to avoid it altogether by demonstration that your surface preparation processes can provide adequate resistance to hydration based on test results from wedge testing using ASTM D3762.

I note SWComposites posting of 24 Sep. Is that a photo of a sample from the manufacturing process...really? Are you saying that this sample was taken from the rubble, or was it from a previous test article? If it was from the rubble, then I am not surprised it failed. If it was from a previous test article, then they knew about how bad their processes were and should have had the sense to halt production until they sorted out the mess.

Does anyone know how the laminate was cured? Was it cured at room temperature, or did they use autoclave processing at elevated temperature?

Regards

Blakmax

Hull was cured in an autoclave after every 1" of fiber wound. Strain and acoustic sensors, and their wires, being wound between layers.

Quote (blakmax)

3DDave. The reason for addressing hydration is that it results in one of the most common forms of bond failure.

I didn't say it should not be considered, I'm saying that there aren't any individual molecule level FEA programs to do it; even multiphysics programs require someone to pre-determine the exact effect. It also doesn't help anything because if hydration is a problem it should not be used at all for the submersible application.

Which is why

Quote (3DDave)

That testing could be done on a smaller sample that applied similar amount of tension and then put that under the same sort of pressure to simulate infiltration into the matrix. One can generate conditions more severe than a full size test in order to discover failure modes for the bond.

was suggested rather than FEA.

"I note SWComposites posting of 24 Sep. Is that a photo of a sample from the manufacturing process...really?"
I understand they wound the whole hull, then trimmed the ends to bring it to exact length, and that was one of the trimmed pieces. I think the guy-that-was-fired said he had taken that picture, but that the sample had been disposed of in the meantime.

The photo is of a piece trimmed off the end of the fabricated cylinder.

I think it was oven cured; typical of a lot of filament wound cylinders.

Concerning this document in the Coast Guard investigation files:



Some of you appear to have figured out who is in the discussion, and I think have a grasp of part of it but the title of the document, and the redactions, and transcription errors leave me somewhat baffled.

1. This appears to be a transcription of a recording of a phone discussion between David Lochridge, Stockton Rush, and maybe Tony Nissen, and two other unknown OceanGate personnel? The title says "Interview" but that is a misnomer. The conversation is from January 2018 so presumably before OceanGate fired David. Stockton Rush pretty well just bulldozed every aspect of the report David presented, and the other attendees don't seem to support David's position in any manner or the transcription is not clear to me. ,
2. There are surprising typos in the document with homophones I would not expect in a 'court reporting transcription' - I have not seen many, so maybe this normal.
3. Any clue on is this from a phone recording? OceanGate recorded all office meetings?
4. Stockton Rush seems highly confident of the data and analysis for his belief of the safety of the hull yet says he won't provide data and analysis for review or he uses some type of obsfucation to deny access, but none of the other attendees seem to push back. Very odd review/discussion dynamic for the report David submitted and rather calmly defended.

I find the dynamic indicated to be odd for the presumably technical attendees not seem to have access to the analysis Stockton said he had, and no one but David asked to review the data. So, were the others in agreement with Stockton? Were they just numbed to questioning Stockton's logic and passion? I have seen that dynamic before with a strong-willed CEO, so I get it slightly. But there seemed to be a definite one-sidedness to the interactions of the attendees.

Quote:

I find the dynamic indicated to be odd for the presumably technical attendees not seem to have access to the analysis Stockton said he had, and no one but David asked to review the data. So, were the others in agreement with Stockton?

It would seem to be wholly consistent with Lockridge's assertiona that everyone else either sucked up to Rush or were kowtowing to Rush. Also, Lochridge has asserted that OG basically hired babes in the woods to do engineering, so Rush's ego wouldn't get bruised, presumably, and only he would hold sway over the design, design process, fabrication, and validation.

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Could be wrong here, but I don't believe Rush had access to a lot of what he was claiming to. It seems to me he had blind trust in the whole thing because the Navy had good results with an old CF hull sub test bed they later retired, and his design was basically a modified version of what they did. Had access to public research docs, but thats about it.

Their dive/maintenance log also paints a picture of inexperience, multiple collisions, and bad hulls. First hull failed after 4 dives and was only caught because the rino lining was being redone. 2nd hull, among other issues, a loud band was heard when surfacing from the 4th dive, and seems no documented instances of inspection exist. That was right around the time OG was hurting for money and were delaying things time and time again.

Quote:

It seems to me he had blind trust in the whole thing because the Navy had good results with an old CF hull sub test bed they later retired, and his design was basically a modified version of what they did. Had access to public research docs, but thats about it.

That's machts nichts; he REFUSED to test ANYTHING to validate his approach. Ronald Reagan already laid down what should be done, "Trust, but verify."

Rush deliberatedly hired inexperienced staff, even though he had tons of experts offering to help, but he rejected all of them because they all wanted testing to be done.

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Testing did get done, just the bare minimum to satisfy what Rush wanted, and no more. Failures of carbon domes is what led him to titanium domes as well as what led to the idea of acoustically monitoring it for cracking. Being told they would have heard the failure creeping up on the 1/3rd scale had they been listening and not just using strain sensors cemented his thinking that they'd hear it before it is too late.

Testing the full size to failure is the only thing they didn't do unmannned.

Rushing the build and blocking inspections most likely meant he knew there were issues, just wanted to hide them and let those who don't know any better cover it up. Is full NDT of 5" thick carbon fiber even possible?

Not that I don't think full destructive testing needed to be done and CF was a poor material choice, but there's a wholye lot more to the failure than just that.
Poorly documented modifications to critical structures, a series of collisions, dropped and sanded viewports, and assembly issues before dives so bad that the front dome fell off. The maintenance history of that sub paints an interesting picture of both hulls.

None of those things contributed to this failure. A CF failure would have pinched the structure in the middle. The domes were intact so they didn't fail. A viewport failure would not have crushed the CF tube. It is apparent that the sub failed at the connection between the CF tube and Ti dome. The sub had made several dives to depths so the joint was strong enough. The question now is what caused it to weaken?

A fundamental CF failure would have been in the middle. A localized failure would have produced torn metal on both the rings in an asymmetric manner, not just on the rear.

Ideally the adhesive joint should not have been the place where the failure initiated but I think the underlying problem was a design failure to have an elastic match between the titanium dome and the carbon fiber to eliminate the shear and local bending load on that adhesive joint.

The joint survived a few dives. I think it was several years old when it failed. We saw the video of the joint assembly. The surface was as machined. I doubt the dome went straight from the lathe to assembly. That means titanium oxide formed on the surface. That means the joint was sensitive to hydration. Hydration is a time sensitive failure mode.

Quote (Tugbosteng)

It is apparent that the sub failed at the connection between the CF tube and Ti dome

Not so fast... It's not nearly that simple.

Any failure would result in water filling the passenger space at supersonic speeds - effectively a gigantic water hammer - which would be difficult to model and would break all sorts of things.

The adhesive joint as initial failure point is certainly one of the likely possibilities, but we don't know that yet to a certainty.

The fact that the entire hull of the submarine was packed into one dome indicates that the failure initiated on the opposite end.

You're right to not make assumptions. I'm just frustrated because I saw the errors made in the adhesive joint a year ago in the advertising video.

Tug, the ring setting video we saw was of the first dome that was discarded in 2019/2020. A new hull was installed in house reusing the original rings and components with an even worse adhesive job.

The frame/skids were also bolted directly to the hull with steel fasteners. Many impacts to the front skids from hitting bottom, launch deck, and crane mishaps on support boats that lead to skids bending and bolts working their way out of the carbon fiber. . I'm sure drilling into the hull

The frame/skids were also bolted directly to the hull with steel fasteners. > where did you find this info? if they drilled holes into the composite hull then they were really stupid.

Quote:

The fact that the entire hull of the submarine was packed into one dome indicates that the failure initiated on the opposite end.

It's not obvious how much of the hull was packed into the back; there was a large piece of internal structure, the platform that passengers sat on that would have survived the implosion.

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I understand the 'Interview' document a little better now: this is David Lochridge defending his inspection report to Stockton Rush and three other OceanGate employees after the major disagreement on safety of the Titan submersible. The January 2018 date of the interview matches with the claims in the whistle-blower litigation:
https://www.documentcloud.org/documents/23854184-o...

So Stockton's antagonistic demeanor and the silence of the other OceanGate technical team is understandable now - this meeting wasn't a technical review. David Lochridge was already out the door at OceanGate, or soon to be.

SWComposits, I had read it in the maintenance and repair log posted by the USCG in some liks above. I'm away from my PC, but I'll look through it agaín real quick and try to copy and paste some of that info.

Edit:
Direct link to log: https://media.defense.gov/2024/Sep/20/2003550785/-...

Mobile screenshot of mention of Hull to frame fastening via bolts.
Thread inserts into the hull. (This was the old hull just around when they found the crack and a month before it was decided to replace it. Modification was likely carried over to the new hull)



Dives and dive notes are the top few pages. Repair logs are below. Dates, dive numbers, etc available to cross reference damage with dives, dive depths, and dive locations.
The closer you look to some of the photos they've released in their shop you can indeed see they've used fasteners to attach directly to the hull, as well as some other modifications that have been done to the hull and domes.

I'm sure more detailed drawings/photos exist but those are not public at the moment.

In the lower portion on the interior of the hulls, they had also drilled for and installed strain and acoustic sensors. Some were surface moint, but one photo of their monitoring system was released during assembly that does show sensors mounted into the hull

Edit 2: Attached document of maint log.

https://files.engineering.com/getfile.aspx?folder=...

Quote:

The fact that the entire hull of the submarine was packed into one dome indicates that the failure initiated on the opposite end.

I don't think it was. There was a substantial structure beneath the floor to hold the high-pressure air tanks. It's about the same size as the material shown in the photo. Even Rush would appreciate the problems that the tanks would cause if they were loose and the sub rolled onto its side with him in it.

I don't believe anything was bolted to the carbon fiber nor any holes drilled into it. AFAIK mounting was only to the titanium rings or the domes.

I need to hit the Submit Post faster to avoid being overtaken.

Brian Malone: Agreed. In my scanning of the 'Interview' document I think I recall the phrase "exit interview" somewhere. With redactions it's hard to keep up with who may be saying what (other than Rush), but I gathered someone from HR called a final meeting to try and stave off Lochridge's dismissal. And the purpose of the recording was CYA for OG to justify cause for the firing. There's a detailed rehashing of the technical disagreement (with a lot of Rush rationalizing his technical bases for dismissing Lochridge's concerns- consciously 'for the record' in tone), and at the end Lochridge(?) agrees there's no 'path forward' for him with the organization, which would be a key outcome for HR's files. If it was an HR meeting that could color the technical team's participation because they were presumably included only to clarify the circumstances surrounding the Rush/Lochridge dispute rather than adjudicate it in that forum.

What struck me is Rush's conviction he had designed around ANY possibility for catastrophic failure modes, along with his utter contempt for conventional subject matter expertise. So the hubris of Rush met its nemesis in the similarly unsinkable Titanic- if this story appeared as a modern techno-Greek-tragedy the critics would probably dismiss it as far-fetched or derivative.

drwebb - yes, the confidence and conviction Stockton Rush had for the hull safety and design /testing method(s) is on one hand admirable: he is all-in with the design and believes in it and is the principal pilot of the vehicle, but on the other hand: this is tragic due to the known failure and loss of life of Stockton and those on board who trusted the vehicle and Stockton. Definitely a reminder that engineering requires confidence and some level of swagger but when faced with multiple inputs for caution maybe a step back for reassessment is warranted.

I wouldn't call blind arrogance admirable at all. Yes he put his money (and life) where his mouth was but his absolute disdain for other opinions or erring on the side of caution for such a dangerous environment is nothing to parade. He's just another rich person who, due to their money, thought they were the smartest person in every room and killed people because of that delusion.

RVAmeche yes, your analysis is true. And I believe others have posted similar.

The NTSB has presented its materials analysis report of both Titan hulls, they tested the cut-offs as well as the wreckage.

https://media.defense.gov/2024/Sep/25/2003553505/-...

This may have already been known/discussed, but the NTSB showed that the two hulls were of completely different design: the v1 hull was monolithic (?) while the v2 hull was a series of shells bonded to each other with adhesive. Evidently these adhesive joints mostly failed during the implosion and the debris therefore consisted of the fragmented individual layers.

Interested to hear from those of you with CF experience regarding these findings.

Karl Stanley summed up the problem with Stockton Rush's reliance on acoustic monitoring in one of the emails he sent to Rush in 2019 (after hearing sounds in the original hull that OceanGate eventually removed from service):

Quote (Karl Stanley)

I also think you are relying too much on all the data, experts, testing etc that you cite. If the hull has a defect (which I believe strongly it does, as indicated by the sounds being concentrated in one area) the value you are placing on your "terabytes of data" goes out the window. If your next dive confirms that the sounds are concentrated in one area, is there any other conclusion than that one area has some sort of defect ?? Short of cutting the hull apart or testing it in a chamber to failure, how will you know what that defect is? If you don't know what the defect is, how can anyone predict how the hull will behave?

https://media.defense.gov/2024/Sep/25/2003553429/-...

The 'V2' hull was wrapped and cured in stagess a direct response to the large amount of internal delamination/porosity seen in the first hulls constructed (both full scale and test) which were wrapped and cured in one go, using a wet layup. This decision is covered in other documents released as part of the hearing.

I would think that obtaining the same strength as a monolithic part would be possible, given sufficient/correct prep of the in-place cured surface... but I've only ever dipped my toe in the composite design pond, I wouldn't call myself an expert.

Oh my, it gets worse:



Not only are there nasty wrinkles that significantly reduce the compression strength, but some idiot decided it would be a good idea to machine them flat, thereby cutting the very fibers they are counting on to carry the load. UGH.

And then this gem:



A "nice" planar disbond along the adhesive line. Great.

The hull fragment photos later in the doc show the hull clearly disbonded along the adhesive layers. Probably too complicated to tell if that was the initial fracture or not.

The fabrication methods shown were machine-controlled layup systems over a metal mandrel by companies that seem to be specializing in fiber-reinforced fabrication. What causes the wrinkles and delaminations and air pockets? Is it heat effects due to the exotherm of the binding resin or heat used during curing? Is air trapped within the wetted fibers during winding? Is the 5-inch thickness difficult to cure evenly?

Quote (Brian Malone)

Is the 5-inch thickness difficult to cure evenly?

Most definitely. That's why they changed to the multi-cure approach in the first place.

The fabricator of the hull was definitely experienced in CFRP mandrel-wound fabrication, but I'm not sure they (or potentially, anyone on planet earth) were experienced in mandrel wound composite structures of this thickness. A lot of these problems are directly due to the difficulty in winding a part with walls this thick and getting a very low void result.

I think this is compounded by the fact that the overwhelming majority of mandrel wound CFRP pressure vessels are subjected to internal pressure in service. You would never want there to be voids in the layup, but if the assembly is under tension, voids are going to have much less negative impact on performance.

This appears to me in order to limit air entrapment and voids the layup should have been done in a vacuum chamber. The resin obviously would be degassed and the fiber stock would be allowed to outgas before starting the wrapping. The continuious feed-stock would have to be degassed and passed into the fab chamber. And the layup process would have to be fully automated; which it appears this is already the case for FRP-type cylinders. There are large vacuum facilities available. Are any CFRP structures fabbed in a vacuum environment?

That's a great way to make an already expensive process more expensive by a factor of probably at least 3.

That also wouldn't solve the problem. Epoxy outgasses when it cures. Control of negative pressure on the parts is a critical aspect of making composite parts successfully. This isn't an issue on smaller components because the outgas products can migrate through the matrix as the part cures- but the thicker the parts are, the longer that takes, and it is possible to cook CFRP parts for too long and negatively impact net properties.

There is an upper limit to how thick you can make CFRP parts.

SWC, I see only 4 fibers of many cut by the machining. Do you think the cutting of the 4 fibers compromised the strength more than allowing the defect to continue through the rest of the layup?

The cut fibers,
- cause a local stress concentration in the laminate as load has to shift to adjacent layers,
- cause a stress concentration in the adhesive bondline, which is already compromised by porosity, voids and general poor quality

How much the cut fibers degrade the overall strength is near impossible to predict, without some test data to calibrate the prediction.

The fiber waviness thru the thickness results in reduced compression strength (like a pre bent column with a axial compression load). This is also hard to predict.

And they apparently designed the laminate to wildly optimistic ultimate strain levels (that essentially assume perfect laminates with no defects or variations).

Then they essentially fatigue loaded the hull to very high strain levels by repeated trips to depth. A hull that had lots of defects in it.

So OG was iterating the hull design and using the only hull for missions. And they had changed hull manufacturer from Spencer Composites to either ElectroImpact or Janicki. Has the manufacturer been determined? Without testing an actual hull to implosive failure with full instrumentation I do not see how they could have confidently had an acoustic and strain signature that could be used in a predictive manner. I think if the design team had video, acoustic and strain data of a full size hull implosion, the speed and totality of such an event would have been real and not theoretical. The apparent normalization of implosion risk might not have occurred and more caution would have been used for proceeding to manned missions to full depth.

Have any photos of the interface rings been presented? I have zoomed in on the wreckage photos and rhe limited view of the hull interface recess in the rear ring is pretty obscure. The front ring hasn't been shown, has it?

@TugboatEng in addition to SWC's comments above - that's not 4 fibers cut; that's millions of cut fibers.

Published docs show they were using roughly 133 layers per inch. Each layer is a wrap of whatever tow they used - that's an unknown, 18k or 24k tows that are 25mm or so wide would a typical choice for a fiber pressure vessel. That means 24,000 fibers per layer x 8 layers cut x depth of that discontinuity in the thirds axis. It's a lot of fibers.

The two reports on the NTSB website go into more detail than the summary on the USCG MBI website. The outer surface was very wavy and there were very many locations where the wrinkles had been ground to allow the next layer to start without wrinkles.
https://data.ntsb.gov/Docket/?NTSBNumber=DCA23FM03...

The NTSB report noted a loud bang at the end of dive 80 (after the sub had surfaced), which resulted in a noticeable change in the strain response of the hull (including a new nonlinearity that was shown at the start of the next dives). The NTSB report also noted that the adhesive surface between the end of the hull and the ring had a rubbed beginning near the base of layer 4 and continuing radially inward. This may indicate that about 3/5 of the adhesive had disbonded long before the failure.

Failure sequence guess:
1. Event at the end of dive 80 causes significant damage, either to the adhesive or hull itself.
2. Dives 81-83 show signs of this damage and might slightly increase it, but not enough for failure.
3. Sub is store outdoors for the winter and then handled roughly (towed on LARS behind the ship; at least 3 upset events while towing in addition to the banging of the waves) - this exacerbates the damage so the sub is no longer suitable for full depth.
4. Sudden implosion without warning on dive 84, due to adhesive disbonding between the hull and end rings and/or buckling of the hull (which had voids, delaminations, waviness, and cut fibers to begin with, and some of these weak points had likely grown due to the cyclic load and impacts suffered by the hull).

Carbon fibre flaws...

https://www.design-engineering.com/engineers-testi...

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-Dik

From jmec87's link:



The inner location flange failed in shear as the bond between the hull and some failed which is expected. But the outer flange failed in bending and bent outwards.

Having the two flanges is a terrible design as it traps air and doesn't let excess adhesive flow out.

Wouldn't the flanged design be a benefit if the relative compressive response of the hull cylinder ends and the interface rings can be matched. I believe the necessity for this behavior was discussed by 3DDave at 9//2024. The inner flange would limit the shear load on the adhesive. Mechanical interlock of the hull ends to the interface rings would be a necessity. Regardless of any 'bang' that may have been heard, the acoustic monitor location diagrams don't show any strain instrumentation at the interface surfaces or on the interface rings. The sensor are along axial lines of the hull and arcs of the end domes, and at the circumference of the inner edge of the viewport. Mechanical failure at the interface zones was not being monitored. The epoxy is wiped clean off the forward interface ring.

Quote (Brian Malone)

And they had changed hull manufacturer from Spencer Composites to either ElectroImpact or Janicki. Has the manufacturer been determined?

According to Factual Report 24-011, ElectoImpact[sic?] did the winding and Janicki did the curing.

The cross-sectional photos showing the fiber waves was not filament wound. You can see that unidirectional prepreg tape was used because the fiber layers are very uniform thickness with no visible tow structure. ElectroImpact makes fiber placement machines, which can use slit tape. But even there you will generally see some variable gapping between slits within the tape layer.

However, thick-walled cylinders are one of the most challenging structures to make from prepregs because prepregs are usually about 5 to 10 percent thicker than the final cured ply thickness. This means that any compaction that occurs during cure will result in wrinkles and waves in the fiber. Compacting a cylinder means reducing its outer diameter, and thus circumference. Carbon fibers are among the stiffest material known. They don't compress anymore than about 1% to failure at max load. Wet filament winding uses low viscosity resins so that full compaction occurs during winding (due to fiber tension), so wrinkling is generally not an issue.

The more I see of it the more I become convinced that the hull layers could just as well be slathered with mold release between each step and seen no difference in performance. It appears little better than friction was carrying the shear loads.

I think I see why the outer flange failed in tension. Notice that it's still attached in two locations roughly 180 degrees apart. The green circle represents the dome and the red oval is the shape of the CF tube as it failed. Sorry for the crude drawing, in the shipyard killing time.

In the shorter report (55 pages) on the ntsb site, this image is presented:


Further images zoom in closer, but the bottom line: a shift in the strain gage vs. load (load=depth which is analogous to external pressure) occurs on a number of the gages recorded (and still functional) across dive 75. Dives 81 through 83 seem to show a nonlinear "hysteresis loop" in the strain vs. load curve, i.e. the strain response follows a different line depending on whether the craft is ascending versus descending. Which would be a major red flag, you'd think? Except, according to testimony, nobody at OG thought to plot strain vs. depth, nor to overlay the traces...they just plotted strain and depth vs. time over the duration of each dive.

Everywhere you look, you see ignorance, hubris and outright negligence.

edit: oh, and failed strain gages were brushed off, no attempt made to figure out why they were no longer working.

Remember that the failure did not occur with the CF tube collapsing in the middle. It seems that Stockton Rush was not incorrect about the factors he spoke about. Instead, there were other factors that doomed the tube. Specifically, in my opinion, this was the bond between the tube and domes.

btrueblood Dive 80 exhibits hysteresis so the effect does not appear to have happened exclusively at Dives 81 thru 83. Wouldn't more info (temperature, system electrical stability, etc.) and analysis be required to determine significance of any offset? Does the NTSB report state why the strain response of these last dives is presented?

Edit - Now I see the differing load/unload offset of the Dives 81 thru 83. Dive 80 has offset similar to Dive 75. So possibly Dives 76 thru 79 were not to 1000 meters, thus not included in the analysis?

If the tube had the integrity of a wet noodle so all loads were held by local bending at the interface with the rings then the glue joint there would be the sole cause of the failure. OTOH, had the tube remained fully rigid, as the rings appear to be, then no more glue would have been required than was used to hold the domes to the ring.

I think the actual failure is somewhere in between with failure of the tube to retain stiffness due to inter-layer mold release putting unnecessary loads on the glue, much like a weak flooring system allows enough flex to pull away from the edge supports.


---

Dives 81-83 are interesting because the hull response is no longer a straight line at the start of the dive above 300-400 meters (nice of them to use fat dots.)

The hysteresis on all dives is likely because the hull changed temperature during the dive.

Quote (Brian Malone)

Edit - Now I see the differing load/unload offset of the Dives 81 thru 83. Dive 80 has offset similar to Dive 75. So possibly Dives 76 thru 79 were not to 1000 meters, thus not included in the analysis?

OG did not restart counts on dives between V1 and V2. Only dives 2000m and below on V2 were 63, 65-70, 73, 75-76, 79-83, and the implosion dive 88.V2 began its diving with dive 50. V2 dives were mostly 200m or less test dives, mostly at depths of 1-10m. Two aborted dives around 1300m and 1700m thanks to thruster failures. v2 made ONE system test to under 2000m before paying passangers were taken to 3840m.


Thruster, drop weight(lots of manual rocking of sub to get weights to fall off), collisions, fires, and sensor failures were plentiful on deep dives, so the data is not great to begin with.


Edited to correct grammar.

There is much more evidence against adhesive failure as primary root cause that there is for it at the moment.

None of the adhesive bond line faces documented thus far exhibit the signs of an adhesive failure in shear; all indicate failures in tension.

Tension failure of the adhesive can't be the first point of failure.

There are areas where the failure isn't in the adhesive layer but at the bond to either the carbon fiber or the titanium. It's not possible to tell if that is tension or shear.

Were any traces of adhesive found on the OD of the outer most layer and ID of the inner? A few of the photos of the recovered wreckage made it look like they did bot have complete coverage of adhesive. I think one photo showed a clean line right up to only about half of the outer layer. V1 had "unsightly" adhesive ground off wherr it squeezed out at the rings to cylinder interface. Rush's mindset of not worrying about the sealing surfaces because the pressure will be keeping the domes and flange squeezed on only makes me wonder if they would have taken steps to prevent adhesive squeezeout when fitting the flanges to the V2 hull.

If there was a lack of adhesive there, I wonder if water slowly worked its way to inbetween layers of the cylinder from the machined end. The sensors with acoustic events were right there near the interface.

Short of gaps allowing water intrusion, how could the adhesive bond fail under pressure and lead to the implosion?

If you watch the video of the assembly, the adhesive joint was clearly not properly prepared. The surface was as machined. Metals that form passive layers such as aluminum, stainless steel, and titanium need to be grit blasted immediately before bonding to remove the passive oxide layer.

Photos of the rings show that where the adhesive actually made contact with the titanium, it stuck pretty well, whereas there are other areas that are devoid of adhesive, indicating either poor surface prep, or no actual contact with adhesive was made at all.

I'd vote the latter, even though they obviously didn't prep the surfaces well, since they also didn't exactly do a meticulous job of ensuring proper adhesive contact with the entirety of the ring either, given Rush's presumption that everything was in compression, at depth, so one could play loosey-goosey with things like fasteners.

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Tug, the video of the ring being set was of V1 hull. As far as I am aware, no video exists of the rings being cleaned of old adhesive and set on the V2 hull.
It wasn't just as machined either. The VTL the rings were machined on is a few feet away in the background. It probably just got some acetone or contact cleaner spray downs right off the chuck before they began to adhere it and was filthier than a mofo.

Some of the marks on the failed adhesive look like old adhesive that was not completely wire wheeled off as well, so there could also have been adhesive to adhesive bonds. I cannot find those images on the uscg site anymore however. They still have the 55 page materials test up, but not the 70+ page; likely down for more redactions.


Edit: Well well.

Quote (USCG hearing)

The trimmed hull was then bonded to the forward and aft segments. The
segments (and domes) were forged and machined from commercially pure (CP)
Grade 3 titanium (UNS R50550). Illustrations of the aft segment are shown in figures 4
and 5. The hull-facing side of both segments contained an annular C-shaped channel
into which the hull was inserted and butt-joined using an epoxy paste adhesive
(Loctite EA 9394 AERO, also known as Hysol EA9394). The segments and domes
were originally used with the first full-scale iteration of the Titan hull. After that hull
was retired, the remnants of the hull were removed from the segments by machining.

According to a former director of engineering and a written OceanGate
process specification, the segments and hull surfaces were prepared for bonding by
degreasing with methyl ethyl ketone (MEK) and roughening with stearate-free
sandpaper. Contact angle measurements were taken between steps to ensure active
(i.e., non-contaminated) surfaces and particulates were blown away using filtered
shop air (tested by contact angle to ensure it did not introduce contamination). The
adhesive was mixed and applied to both the segment and hull bonding surfaces. The
hull was then inserted into the C-channel. The aft joint was formed by lowering the
hull down onto the segment and the forward joint was formed by lowering the
segment down onto the hull, the entire assembly oriented vertically. Spacers within
the joint controlled the bond line thickness.

Quote:

Most of the adhesive originally used to bond the hull to the titanium segment
had disbonded from the machined end of the hull piece, but there was an
approximately 3.5-inch-long patch where some adhesive bits were still attached,
shown in figures 25a and b. Most of the patch was between 0.030 inch and 0.034 inch
thick. In a smaller region, the adhesive measured between 0.055 inch and 0.064 inch
thick, all measurements performed by caliper. As previously described, the process
for bonding the hull to the segments involved applying excess epoxy adhesive to
both the end of the carbon fiber hull and the flat face of the titanium segment’s Cchannel. The appearance and thickness of the thinner adhesive region was consistent
with a separation at the interface between the adhesive applied to the hull and the
adhesive applied the titanium. The appearance of the thicker patch was consistent
with a separation at the interface between the adhesive and the titanium.

It just gets better and better...

https://www.cnn.com/2024/09/27/us/former-oceangate...

-----*****-----
So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik

From the NTSB reports in the NTSB docket files, Chair's Factual Report 24-012:
https://data.ntsb.gov/Docket/?NTSBNumber=DCA23FM03...

NTSB exhibits an apparent change in stiffness of the hull in their Fig. 35



I believe the 5A sensor group was on an axial line at the mid point of the hull. Refer to page 8 of the sensor layout shown in 'CG-058 Titan AE and Strain Sensor Locations_Redacted:
https://www.news.uscg.mil/News-by-Region/Headquart...

In the CG files there is the early structural analysis by Spenser Composites for the first hull. It has some FEA for the hull but appears not to analyze the titanium interface rings in detail. Has any interface ring analysis been presented?

Edit - missed the image on page 5 in the CG-058 Titan AE and Strain Sensor Locations_Redacted document. FEA of the front dome and interface ring, done by Collier Research. It indicates 29 to 39 ksi for the inner lip of the C channel. For forged titanium component this pretty low. The loading conditions of the FEA would need to be presented.

Quote (Brian Malone)

indicates 29 to 39 ksi for the inner lip of the C channel

For Gr 3 titanium in shear, that window is right on the money

Yes, SwinnyGG, my wording was imprecise. I meant the stress was predicted to be low, well under the yield for titanium.

What's amusing and distressing is that no one at OG had even considered to graph the strain gage data vs. depth, which would have made it obvious that something drastic had occurred on dive 80(?), i.e., the loud "bang"

Potentially worse yet, someone might have suggested the same graph, but Rush might have nixed it.

TTFN (ta ta for now)
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IRstuff,

If by "nixed it," you mean, fired the person, I agree. Rush didn't want to know about any safety issue as he was drowning in debt and needed to get paying passengers, err, crew, to offset the losses. Crew, because it was illegal for him to sell trips to passengers.

It's likely he had fired everyone who would think to make such a graph. I saw a snippit from the HR person; just as maddening what she did.

@TugboatEng, @IRstuff, @3DDave, @SWC, @Swinny, etc. Referencing "Figures 45 and 46" of the "Materials Laboratory Factual Report 24-011_Redacted-Rel.pdf" on page 73 of 79 (at least on the copy I downloaded over the weekend):

I am interested to hear/read others' interpretation of the possible causes of dis-bonding on the forward titanium ring in light of this photographic evidence of the adhesive conditions between the aft section of the cylinder and the aft titanium ring. More specifically, there is evidence (from the visible lines of the various pre-preg winding layers) that the adhesive contacted both the Ti ring and the CFRP cylinder on the outer two 1" co-bonded layers (layers 4 and 5). To put my following questions in context, I have very little experience with epoxy/fibre composites at all let alone being an expert on CF components bonded to Titanium components.

Questions:
1) It is my understanding that a properly spec'd and manufactured cured epoxy joint should fail through the epoxy or through the base material(s) rather than failing at the bonding layer(s) - in what circumstances / under what general conditions would a cured epoxy adhesive joint exhibit areas of failure as shown in Figures 45 b) and 46 a) i.e. failing at either bond layer and through the epoxy?
2) Looking at the fracture regions of the Ti flanges (specifically Fig 45 b) and Fig 46 a)) where the inner flange (i.e. the flange on the ID of the Ti ring) appears to have failed in shear as evidenced by the radial lines or "scratch" marks while the outer flange appears to have failed in a tearing or ripping mode as evidenced by the irregular surface of the outer flange (@TugboatEng has diagrammed above one possible failure geometry) on both the aft and forward rings - there are areas on a single radial cross section (see my red line on Fig 45 b) below, starting at the point the upper part of the ruler intersects the inner edge of the Ti Ring then drawing a radial line outwards to the outer edge of the Ti ring) where there appear to be regions of i) failure between Adhesive and Ti, ii) failure within the Adhesive, iii) failure between the Adhesive and CFRP hull, and iv) again between Adhesive and Ti; the only failure mode I can think of is de-lamination between co-bonded layers 3 and 4 as layers 1 through 3 travel inward during the rapid failure while the rapid release of energy somehow rips layers 4 and 5 outwards but I can't yet conceive of any free-body diagram that would account for the required forces - the only thing I am reasonably convinced of is that the failure could not have started through this specific radial cross section. Does this type of failure look familiar to anyone and if so, would you be so kind as to explain it?

- NOTE: red line and text markup is mine.

@DirteJoe, (for other readers) The first quote in your recent post from Sept 29, 2024 is from Pgs 5 & 6 (of 79) of Factual Report 24-011 and the second quote is from Pg 9 (of 79).

To any engineers with experience in acoustic monitoring (ideally with experience in measuring localized acoustic energy in rigid structures) - in the event of any acoustic-energy/emission-producing event in a rigid structure, would/should we expect to see that event measured at every measuring point (i.e. any Acoustic Emissions(AE) sensor) attached to the rigid structure? I assume that the event's signature would be attenuated and delayed as a function of the distance the AE sensor was from the location of the event and the medium(s) through which the energy was propagated but the bottom line is that I would expect to see that signature in all sensors. I am specifically referring to the testimony of Phil Brooks (Dir of Engineering at Oceangate (OG) from ~Jan 2021 to the accident **Edit: some time in 2023 after which time he resigned according to his testimony** whose focus was ostensibly on the electrical/electronic systems which included the RTM system) related to his explanation of the "strange" AE signatures (see https://www.youtube.com/live/fQc_9sNzx3k?si=B45uKH... around timestamp 6:25 and forward) across multiple sensors - specifically the AE Sensors 1, 3 and 5. In my opinion, his testimony in this regard generated more questions than answers. From the sensor location diagrams found at https://media.defense.gov/2024/Sep/23/2003552110/-... , Sensor groups 1 and 2 (details are apparently on File-0001097 which I can't find) are located very close to each other on the forward Ti dome. Groups 3 and 5 are on the same side of the hull but group 4 is closer to group 1 and group 3 is closer to group 2 and groups 4 and 2 record similar AE events - I don't have enough information on which to base a conclusion but I can't find a coherent theory that would explain this large of a discrepancy of AE measurements by ostensibly the same spec sensors without the AE sensors at locations 1, 3 and 5 to be damaged/out-of-spec/improperly-installed. I hope the NTSB's full investigation will shed more light on these discrepancies.

GF -
(I haven't dug deep into all the reports, but)
- the bond between the end of the composite hull and the Ti ring (the surface shown in the photos above) is completely useless structurally; trying to transfer load onto the end of a thick laminate is just not done by anyone with a clue; it could only be useful to seal the joint from water intrusion.
- the only bond joint that will have any structural purpose is between the Ti ring flanges and the surfaces of the composite hull; this is a typical shear joint. However, if there is differential radial displacement between the composite hull tube and the Ti ring that will introduce through thickness tensile stresses with are not desirable in a bonded joint.
- they claim to have used "spacers" to try to control the adhesive thickness; given all of the other poor fabrication practices shown in the various reports, I have no confidence that they properly used the spacers nor does it appear they actually inspected the bond lines.

AE just records internal "sounds".
It can sort of sometimes be used to triangulate the location of the sound.
It cannot indicate what created the sound. Relying on it for this application is just IMO foolish.

Quote (GreenFields)

1) It is my understanding that a properly spec'd and manufactured cured epoxy joint should fail through the epoxy or through the base material(s) rather than failing at the bonding layer(s) - in what circumstances / under what general conditions would a cured epoxy adhesive joint exhibit areas of failure as shown in Figures 45 b) and 46 a) i.e. failing at either bond layer and through the epoxy?

There are three primary modes of failure for any adhesive joint:

1) Failure of the base bonded material. In this case, the adhesive itself does not fail; the base material(s) being bonded by the adhesive fail. This is easy to spot, as you wind up with one part having a perfect layer of adhesive still stuck to it, with a layer of material from the other bonded part still stuck to the adhesive on the far side. The failure happened when the surface of one of the parts was ripped off, without the adhesive coming apart.

2) 'Cohesive' failure, ie failure of the adhesive itself. This manifests as two parts separated, with each having a thin layer of remaining adhesive bonded to the surface at the joint.

3) 'Adhesive' failure, ie failure of the joint at the interface between the layer of adhesive and one of the parts.

These failure modes can be, and in fact almost always are, mixed. It would be very rare to test a joint to failure and have only a single one of these failure modes appear, unless certain conditions apply (very small parts, selected adhesive much, much stronger than base bonded materials, etc).

In the pictures we have of the failed bonded joints between the Ti rings and the composite hull section, we can see many large areas of adhesive failure, and a few areas appear to be cohesive failure as well. There do not appear to be any areas (at least none that I've seen so far) which exhibit failure of the base bonded materials. It is possible that some of the adhesive surfaces visible on the titanium rings (remember, if it's adhesive on the ring, the surface we can see was bonded to the CFRP shell) have a very thin layer of the composite resin still bonded to them. That resin is effectively transparent when it's very very thin, and it's possible there is a layer a few thousandths thick still bonded to the adhesive itself. So we can't completely eliminate base bonded material failure in these areas. All we can do at this point is, based on what we see elsewhere, state that it's unlikely.

There are whole engineering PhD thesis written on why and how adhesives fail, but in short:

Adhesive failure is really bad. It almost always indicates one of two possibilities; either the wrong adhesive product was selected (every adhesive can't properly bond every material, obviously) or the bonding faces were not properly prepared prior to bonding.

Based on the available information about the process used, those of us that have been following this for a while are not shocked that there are large areas of adhesive failure visible on both the titanium and CFRP parts of the assembly. All signs indicate that the surfaces were not well prepped when they were assembled.

Quote (GreenFields)

2) Looking at the fracture regions of the Ti flanges (specifically Fig 45 b) and Fig 46 a)) where the inner flange (i.e. the flange on the ID of the Ti ring) appears to have failed in shear as evidenced by the radial lines or "scratch" marks while the outer flange appears to have failed in a tearing or ripping mode as evidenced by the irregular surface of the outer flange (@TugboatEng has diagrammed above one possible failure geometry) on both the aft and forward rings - there are areas on a single radial cross section (see my red line on Fig 45 b) below, starting at the point the upper part of the ruler intersects the inner edge of the Ti Ring then drawing a radial line outwards to the outer edge of the Ti ring) where there appear to be regions of i) failure between Adhesive and Ti, ii) failure within the Adhesive, iii) failure between the Adhesive and CFRP hull, and iv) again between Adhesive and Ti; the only failure mode I can think of is de-lamination between co-bonded layers 3 and 4 as layers 1 through 3 travel inward during the rapid failure while the rapid release of energy somehow rips layers 4 and 5 outwards but I can't yet conceive of any free-body diagram that would account for the required forces - the only thing I am reasonably convinced of is that the failure could not have started through this specific radial cross section. Does this type of failure look familiar to anyone and if so, would you be so kind as to explain it?

Before you do down the rabbit hole of trying to explain every mark or striation you see on the surfaces of these parts you have to keep in mind the external conditions the assembly was subjected to at the time of the failure.

At the time the hull imploded, the sub was at a depth of approximately 11,000 feet. At that depth, the water pressure is roughly 4900 psi. The OD of the hull was 66 inches, giving us about 3400 in² of cross sectional area. Do the math... the force pressing the end ring onto the hull was in the neighborhood of 16.5 million pounds. 8,300 tons.

The entire assembly was under an extreme amount of static load, with no structural redundancy of any kind. As soon as any component reaches a point where it can't support that extreme load, the resulting implosion happens extremely fast. We're talking about an event that was over in milliseconds.

The point is - an event involving the near-instantaneous release of that much potential energy is very, very chaotic. Modeling this failure with the best tools we have available would still be very difficult, and would likely leave a lot of unanswered questions.

In other words, we probably all agree that all the flanges being ripped off is peculiar, but an event this energetic is very difficult to model and why exactly the flanges failed the way they did is something we will potentially never know.

Quote (SwinnyGG)

The entire assembly was under an extreme amount of static load, with no structural redundancy of any kind. As soon as any component reaches a point where it can't support that extreme load, the resulting implosion happens extremely fast. We're talking about an event that was over in milliseconds

This where I think Stockton Rush lost some of the necessary caution: it appears to me he normalized the very real totality of an implosion because no test to failure was done on the full size vehicle. Early, the 1/3 scale with CF domes was tested but the failure was a punch thru of one of the domes and not a total hull crush. The V1 hull was replaced due to cracks. It did not implode. It appears to me the relative success of the V1 and rebuilt V2, and OG FEA strengthened the over confidence Stockton had in the design factor/margin of the system.

I agree, that was one of the major failures.

The real root cause in my estimation is something I see in junior engineers A LOT.

His entire safety process was based on the idea that you can manufacture a critical component using edge-of-envelope techniques and materials, and end up with a result that has net design properties on the first try, with nearly zero process development.

I don't disagree that they would have been well served to much more thoroughly test the end product itself- but in my estimation, the fact that they were using the filament winding process right to the upper limit of what can be done with existing equipment was never even acknowledged, let alone evaluated as something that needed to be tested.

Rush just assumed that his hull would have net properties equivalent to much thinner, easier-to-fabricate structures, and never did any process eval to figure out if that was true.

Quote:

It cannot indicate what created the sound. Relying on it for this application is just IMO foolish.

The one thing that Rush did semi-correctly was the inclusion of the strain gages, but, for whatever reason, no one did any real analysis with the data. Otherwise, both the hystersis in the strain and the changes after dive 80 would have rung alarm bells. This was possible consequence of hiring only junior engineers, who are open to new ideas, but don't know what the bad ideas learned through experience are.

Quote:

Rush just assumed that his hull would have net properties equivalent to much thinner, easier-to-fabricate structures, and never did any process eval to figure out if that was true.

I think that was part of it, but there was a deep disdain of "conventional" design and verification, coupled with possibly different massive misunderstanding of why there are no other failures of DSVs, which was due to the massive amount of testing that he disdained, that he interpreted as being extremely overly cautious to the point of stifling "innovation."

Even smart people have massive blind spots.

TTFN (ta ta for now)
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I have been watching the MBI session(s) in the links in Greenfield's post above, and realize I was wrong about OG testing to implosive failure. Phil Brooks, Dir. Of Eng. for a time, testifies OG tested the 1/3 scale hull #1 to implosive failure. The suddenness and totality was fully understood by all at the test. The resounding ringing in their ears left no doubt what had happened in the test chamber. The following 1/3 scales were tested to failure but did not implode. He indicates somewhat clumsily OG did plot strain data verses depth and not just time and he, Stockton and other OG staff reviewed the data. He said he is/was not an expert at interpretation of strain data but he/they looked for non-linear behaviors, shifts and offsets and could see in the 1/3 scale data definite, clear indications of impending failure.

I have become a stuck record with thinking the OG team had normalized the risk of implosion due to a lack of representative events and data; I have to reconsider this. It appears to me they did do testing (certainly, some of it was sloppy and incomplete), they had analysis but either the data and analysis does not scale with the final hull fabrication or the failure mode was not captured by the testing done.

Phil Brook's testimony is interesting.

Quote (Brian Malone)

they looked for non-linear behaviors, shifts and offsets and could see in the 1/3 scale data definite, clear indications of impending failure.

This is an interesting revelation.

But it seems the next step for Rush et. al. was to just assume that since they had heard some noises from the scale hull prior to failure, they should just listen for those same noises in the full scale hull and everything would be fine unless they heard the same 'signature'.

If that's the logical path they took there definitely seems to be a scale model to full scale correlation/characterization step missing here.

Phil Brooks does say OG went straight to the "multi-cure" hull for the V2 hull and did not build a 1/3 scale test hull of this construction. I am pretty sure he confirms none of the 1/3 scale hulls were successful at reaching "Titanic" depth.

Quote:

But it seems the next step for Rush et. al. was to just assume that since they had heard some noises from the scale hull prior to failure, they should just listen for those same noises in the full scale hull and everything would be fine unless they heard the same 'signature'.

But, they did hear a massive bang on Dive 80 (?), correlated to the change in the strain gage data, both of which they ignored. Both should have been indications that the hull was compromised in some way.

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Fully agree.

The only conclusion I can find (this is 100% conjecture) is the the 'loud bang' heard during dive 80 was assumed to not be a major problem because it didn't precisely match some 'ideal' sound signature they were looking for based on the test results from the 1/3rd scale tests to failure.

This whole thing reads to me as 'we heard a very specific thing during 1/3rd scale testing, as long as we don't hear that specific thing again we're good' as opposed to 'any signal above a certain threshold should trigger some sort of re-evaluation of the hull'.

https://www.youtube.com/live/0FckuxRInJI?si=z_xF0M...

Dr. Kramer of NTSB in his presentation, states what has been pointed out already: he did not receive data plotted strain vs. depth and tactfully states " it is a matter of opinion " whether OG's analysis method would have allowed for proper evaluation of hull behavior.

Phil Brooks states Electroimpact dictated the multi-cure hull fabrication method. Stockton was not keen on the method but acquiesced because Electroimpact would not take on the project if not a multi-cure design. I have not seen any Electroimpact personnnel testifying in the MBI videos.

webinar: A Forensic Analysis of the Titan Submersible Implosion

https://us02web.zoom.us/webinar/register/WN_wtagFx...

Quote:

The only conclusion I can find (this is 100% conjecture) is the the 'loud bang' heard during dive 80 was assumed to not be a major problem because it didn't precisely match some 'ideal' sound signature they were looking for based on the test results from the 1/3rd scale tests to failure.

That just makes everything even more moronic. Since when did a sample of one determine any sort of behavior?

I had a long drive today, and was thinking about Rush's gleeful exposition about "breaking the rules" and "progress" and I think that Rush had rushed to associate correlation with causation. While progress often does entail "breaking the rules," breaking the rules does not always entail progress, in most cases, in fact, it results in death or severe injury.

You would think that someone trained in engineering ought to know better, but apparently he was a legend in his own mind. Although, I suppose, he did, in fact, turn into a legend, albeit of a cautionary tale type.

TTFN (ta ta for now)
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There is nothing cavalier about his actions.

-----*****-----
So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik

Quote:

There is nothing cavalier about his actions.

Five people dead in a preventable incident; cavalier

TTFN (ta ta for now)
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cavalier: marked by or given to offhand and often disdainful dismissal of important matters.

IRS... just in case some people thought his actions were positive, or admirable in any fashion.

-----*****-----
So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik

My company once leased a boat. It was so bad I decided to view their website. The website had a story about the architect claiming that he was so good he could design a tugboat on a napkin. I could tell that is exactly what he had done. That architect somehow found a winch manufacturer that was even worse than he was. Low quality engineers attract low quality vendors. It creates a perfect storm.

Quote:

cavalier: marked by or given to offhand and often disdainful dismissal of important matters.

I think that describes my opinion of Rush to a T; he absolutely disdainfully dismissed all the experts that told him he was full of crap and needed to prove his concept with test to failure. His dogged pursuit of "breaking" rules, because he failed to recognize that while advances often came from breaking the rules, arbitrarily breaking the rules often does not confer advances, merely death or dismemberment.

TTFN (ta ta for now)
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