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Tourist submersible visiting the Titanic is missing Part 2
45

Tourist submersible visiting the Titanic is missing Part 2

RE: Tourist submersible visiting the Titanic is missing Part 2

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

RE: Tourist submersible visiting the Titanic is missing Part 2

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.

RE: Tourist submersible visiting the Titanic is missing Part 2

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!

RE: Tourist submersible visiting the Titanic is missing Part 2

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

RE: Tourist submersible visiting the Titanic is missing Part 2

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!

RE: Tourist submersible visiting the Titanic is missing Part 2

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.

RE: Tourist submersible visiting the Titanic is missing Part 2

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."

RE: Tourist submersible visiting the Titanic is missing Part 2

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

RE: Tourist submersible visiting the Titanic is missing Part 2

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.

RE: Tourist submersible visiting the Titanic is missing Part 2

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

RE: Tourist submersible visiting the Titanic is missing Part 2

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


RE: Tourist submersible visiting the Titanic is missing Part 2

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!

RE: Tourist submersible visiting the Titanic is missing Part 2

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

RE: Tourist submersible visiting the Titanic is missing Part 2

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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RE: Tourist submersible visiting the Titanic is missing Part 2

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.

RE: Tourist submersible visiting the Titanic is missing Part 2

"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>

RE: Tourist submersible visiting the Titanic is missing Part 2



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.

RE: Tourist submersible visiting the Titanic is missing Part 2

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?

RE: Tourist submersible visiting the Titanic is missing Part 2

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".

RE: Tourist submersible visiting the Titanic is missing Part 2

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

RE: Tourist submersible visiting the Titanic is missing Part 2

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

RE: Tourist submersible visiting the Titanic is missing Part 2

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

RE: Tourist submersible visiting the Titanic is missing Part 2

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

RE: Tourist submersible visiting the Titanic is missing Part 2

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.

RE: Tourist submersible visiting the Titanic is missing Part 2

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

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

RE: Tourist submersible visiting the Titanic is missing Part 2

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

RE: Tourist submersible visiting the Titanic is missing Part 2

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.

RE: Tourist submersible visiting the Titanic is missing Part 2

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!

RE: Tourist submersible visiting the Titanic is missing Part 2

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.

RE: Tourist submersible visiting the Titanic is missing Part 2

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...

RE: Tourist submersible visiting the Titanic is missing Part 2

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.

RE: Tourist submersible visiting the Titanic is missing Part 2

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

RE: Tourist submersible visiting the Titanic is missing Part 2

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

RE: Tourist submersible visiting the Titanic is missing Part 2

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.

RE: Tourist submersible visiting the Titanic is missing Part 2

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."

RE: Tourist submersible visiting the Titanic is missing Part 2

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

RE: Tourist submersible visiting the Titanic is missing Part 2

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

RE: Tourist submersible visiting the Titanic is missing Part 2

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.

RE: Tourist submersible visiting the Titanic is missing Part 2

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

RE: Tourist submersible visiting the Titanic is missing Part 2

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.

RE: Tourist submersible visiting the Titanic is missing Part 2

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.

RE: Tourist submersible visiting the Titanic is missing Part 2

^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

RE: Tourist submersible visiting the Titanic is missing Part 2

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.

RE: Tourist submersible visiting the Titanic is missing Part 2

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.

RE: Tourist submersible visiting the Titanic is missing Part 2

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.

RE: Tourist submersible visiting the Titanic is missing Part 2

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.

RE: Tourist submersible visiting the Titanic is missing Part 2

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!

RE: Tourist submersible visiting the Titanic is missing Part 2

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."

RE: Tourist submersible visiting the Titanic is missing Part 2

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.

RE: Tourist submersible visiting the Titanic is missing Part 2

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.

RE: Tourist submersible visiting the Titanic is missing Part 2

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

RE: Tourist submersible visiting the Titanic is missing Part 2

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)
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RE: Tourist submersible visiting the Titanic is missing Part 2

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

RE: Tourist submersible visiting the Titanic is missing Part 2

@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?

RE: Tourist submersible visiting the Titanic is missing Part 2

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

RE: Tourist submersible visiting the Titanic is missing Part 2

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?

RE: Tourist submersible visiting the Titanic is missing Part 2

@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.

RE: Tourist submersible visiting the Titanic is missing Part 2

@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.

RE: Tourist submersible visiting the Titanic is missing Part 2

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

RE: Tourist submersible visiting the Titanic is missing Part 2

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.

RE: Tourist submersible visiting the Titanic is missing Part 2

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!

RE: Tourist submersible visiting the Titanic is missing Part 2

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.

RE: Tourist submersible visiting the Titanic is missing Part 2

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

RE: Tourist submersible visiting the Titanic is missing Part 2

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.

RE: Tourist submersible visiting the Titanic is missing Part 2

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."

RE: Tourist submersible visiting the Titanic is missing Part 2

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

RE: Tourist submersible visiting the Titanic is missing Part 2

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.

RE: Tourist submersible visiting the Titanic is missing Part 2

You are right. I divided 720 by 1.98 slugs, not 720kips, lost 000 there blush 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."

RE: Tourist submersible visiting the Titanic is missing Part 2

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.



RE: Tourist submersible visiting the Titanic is missing Part 2

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.

RE: Tourist submersible visiting the Titanic is missing Part 2

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?

RE: Tourist submersible visiting the Titanic is missing Part 2

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

RE: Tourist submersible visiting the Titanic is missing Part 2

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

RE: Tourist submersible visiting the Titanic is missing Part 2

2

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.

RE: Tourist submersible visiting the Titanic is missing Part 2

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

RE: Tourist submersible visiting the Titanic is missing Part 2

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)
I can do absolutely anything. I'm an expert! https://www.youtube.com/watch?v=BKorP55Aqvg
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RE: Tourist submersible visiting the Titanic is missing Part 2

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

RE: Tourist submersible visiting the Titanic is missing Part 2

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

RE: Tourist submersible visiting the Titanic is missing Part 2

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."

RE: Tourist submersible visiting the Titanic is missing Part 2

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.

RE: Tourist submersible visiting the Titanic is missing Part 2

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.

RE: Tourist submersible visiting the Titanic is missing Part 2

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!

RE: Tourist submersible visiting the Titanic is missing Part 2

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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RE: Tourist submersible visiting the Titanic is missing Part 2

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."

RE: Tourist submersible visiting the Titanic is missing Part 2

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.

RE: Tourist submersible visiting the Titanic is missing Part 2

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.



RE: Tourist submersible visiting the Titanic is missing Part 2

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

RE: Tourist submersible visiting the Titanic is missing Part 2

As was everything else :)

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

RE: Tourist submersible visiting the Titanic is missing Part 2

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."

RE: Tourist submersible visiting the Titanic is missing Part 2

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.

RE: Tourist submersible visiting the Titanic is missing Part 2

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.

RE: Tourist submersible visiting the Titanic is missing Part 2

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."

RE: Tourist submersible visiting the Titanic is missing Part 2

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

RE: Tourist submersible visiting the Titanic is missing Part 2

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.

RE: Tourist submersible visiting the Titanic is missing Part 2

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!

RE: Tourist submersible visiting the Titanic is missing Part 2

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."

RE: Tourist submersible visiting the Titanic is missing Part 2

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

RE: Tourist submersible visiting the Titanic is missing Part 2

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.

VH = πr2L + (4πr3)/3
VH = 3.14159 * 0.842 * 2.54 + (4*3.14159*0.843)/3
VH = 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.

RE: Tourist submersible visiting the Titanic is missing Part 2

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.

RE: Tourist submersible visiting the Titanic is missing Part 2

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.

RE: Tourist submersible visiting the Titanic is missing Part 2

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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RE: Tourist submersible visiting the Titanic is missing Part 2

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.

RE: Tourist submersible visiting the Titanic is missing Part 2

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.

RE: Tourist submersible visiting the Titanic is missing Part 2

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: Tourist submersible visiting the Titanic is missing Part 2

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.

RE: Tourist submersible visiting the Titanic is missing Part 2

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.

RE: Tourist submersible visiting the Titanic is missing Part 2

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.

RE: Tourist submersible visiting the Titanic is missing Part 2

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.

TTFN (ta ta for now)
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RE: Tourist submersible visiting the Titanic is missing Part 2

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."

RE: Tourist submersible visiting the Titanic is missing Part 2

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.

RE: Tourist submersible visiting the Titanic is missing Part 2

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."

RE: Tourist submersible visiting the Titanic is missing Part 2

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.

RE: Tourist submersible visiting the Titanic is missing Part 2

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

RE: Tourist submersible visiting the Titanic is missing Part 2

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."

RE: Tourist submersible visiting the Titanic is missing Part 2

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!

RE: Tourist submersible visiting the Titanic is missing Part 2

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

RE: Tourist submersible visiting the Titanic is missing Part 2

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.

RE: Tourist submersible visiting the Titanic is missing Part 2

Thanks...

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

-Dik

RE: Tourist submersible visiting the Titanic is missing Part 2

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.

RE: Tourist submersible visiting the Titanic is missing Part 2

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.

RE: Tourist submersible visiting the Titanic is missing Part 2

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!!!

RE: Tourist submersible visiting the Titanic is missing Part 2

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?,

RE: Tourist submersible visiting the Titanic is missing Part 2

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.

RE: Tourist submersible visiting the Titanic is missing Part 2

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!

RE: Tourist submersible visiting the Titanic is missing Part 2

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."

RE: Tourist submersible visiting the Titanic is missing Part 2

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

RE: Tourist submersible visiting the Titanic is missing Part 2

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

RE: Tourist submersible visiting the Titanic is missing Part 2

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

RE: Tourist submersible visiting the Titanic is missing Part 2

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!

RE: Tourist submersible visiting the Titanic is missing Part 2

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.

TTFN (ta ta for now)
I can do absolutely anything. I'm an expert! https://www.youtube.com/watch?v=BKorP55Aqvg
FAQ731-376: Eng-Tips.com Forum Policies forum1529: Translation Assistance for Engineers Entire Forum list http://www.eng-tips.com/forumlist.cfm

RE: Tourist submersible visiting the Titanic is missing Part 2

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!

RE: Tourist submersible visiting the Titanic is missing Part 2

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

RE: Tourist submersible visiting the Titanic is missing Part 2

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."

RE: Tourist submersible visiting the Titanic is missing Part 2

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

RE: Tourist submersible visiting the Titanic is missing Part 2

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."

RE: Tourist submersible visiting the Titanic is missing Part 2

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

RE: Tourist submersible visiting the Titanic is missing Part 2

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

RE: Tourist submersible visiting the Titanic is missing Part 2

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? ponder

RE: Tourist submersible visiting the Titanic is missing Part 2

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."

RE: Tourist submersible visiting the Titanic is missing Part 2

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.

RE: Tourist submersible visiting the Titanic is missing Part 2

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.

RE: Tourist submersible visiting the Titanic is missing Part 2

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

RE: Tourist submersible visiting the Titanic is missing Part 2

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

RE: Tourist submersible visiting the Titanic is missing Part 2

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





RE: Tourist submersible visiting the Titanic is missing Part 2

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.

RE: Tourist submersible visiting the Titanic is missing Part 2

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.

RE: Tourist submersible visiting the Titanic is missing Part 2

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

RE: Tourist submersible visiting the Titanic is missing Part 2

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

RE: Tourist submersible visiting the Titanic is missing Part 2

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."

RE: Tourist submersible visiting the Titanic is missing Part 2

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

RE: Tourist submersible visiting the Titanic is missing Part 2

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.

RE: Tourist submersible visiting the Titanic is missing Part 2

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

RE: Tourist submersible visiting the Titanic is missing Part 2

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?

RE: Tourist submersible visiting the Titanic is missing Part 2

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!

RE: Tourist submersible visiting the Titanic is missing Part 2

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.

RE: Tourist submersible visiting the Titanic is missing Part 2

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.

RE: Tourist submersible visiting the Titanic is missing Part 2

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.

RE: Tourist submersible visiting the Titanic is missing Part 2

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.

RE: Tourist submersible visiting the Titanic is missing Part 2

(OP)
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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RE: Tourist submersible visiting the Titanic is missing Part 2

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?

RE: Tourist submersible visiting the Titanic is missing Part 2

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.

RE: Tourist submersible visiting the Titanic is missing Part 2

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

RE: Tourist submersible visiting the Titanic is missing Part 2

I'm thinking more like this.

RE: Tourist submersible visiting the Titanic is missing Part 2

@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.

RE: Tourist submersible visiting the Titanic is missing Part 2

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.

RE: Tourist submersible visiting the Titanic is missing Part 2

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.

TTFN (ta ta for now)
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RE: Tourist submersible visiting the Titanic is missing Part 2

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.



TTFN (ta ta for now)
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RE: Tourist submersible visiting the Titanic is missing Part 2

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=...

RE: Tourist submersible visiting the Titanic is missing Part 2

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

RE: Tourist submersible visiting the Titanic is missing Part 2

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.

RE: Tourist submersible visiting the Titanic is missing Part 2

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.

RE: Tourist submersible visiting the Titanic is missing Part 2

hpaircraft what are some of the techniques used?

RE: Tourist submersible visiting the Titanic is missing Part 2

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.

RE: Tourist submersible visiting the Titanic is missing Part 2

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

RE: Tourist submersible visiting the Titanic is missing Part 2

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?

RE: Tourist submersible visiting the Titanic is missing Part 2

(OP)
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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RE: Tourist submersible visiting the Titanic is missing Part 2

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.

RE: Tourist submersible visiting the Titanic is missing Part 2

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.

RE: Tourist submersible visiting the Titanic is missing Part 2

(OP)
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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RE: Tourist submersible visiting the Titanic is missing Part 2

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.

RE: Tourist submersible visiting the Titanic is missing Part 2

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

RE: Tourist submersible visiting the Titanic is missing Part 2

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.

RE: Tourist submersible visiting the Titanic is missing Part 2

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.

RE: Tourist submersible visiting the Titanic is missing Part 2

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.

RE: Tourist submersible visiting the Titanic is missing Part 2

2
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.

RE: Tourist submersible visiting the Titanic is missing Part 2

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.

RE: Tourist submersible visiting the Titanic is missing Part 2

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!

RE: Tourist submersible visiting the Titanic is missing Part 2

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."

RE: Tourist submersible visiting the Titanic is missing Part 2

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...

RE: Tourist submersible visiting the Titanic is missing Part 2

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."

RE: Tourist submersible visiting the Titanic is missing Part 2

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

"Schiefgehen wird, was schiefgehen kann" - das Murphygesetz

RE: Tourist submersible visiting the Titanic is missing Part 2

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.

RE: Tourist submersible visiting the Titanic is missing Part 2

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

RE: Tourist submersible visiting the Titanic is missing Part 2

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.

RE: Tourist submersible visiting the Titanic is missing Part 2

3
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

RE: Tourist submersible visiting the Titanic is missing Part 2

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

RE: Tourist submersible visiting the Titanic is missing Part 2

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.

RE: Tourist submersible visiting the Titanic is missing Part 2

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.

RE: Tourist submersible visiting the Titanic is missing Part 2

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.

RE: Tourist submersible visiting the Titanic is missing Part 2

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)
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RE: Tourist submersible visiting the Titanic is missing Part 2

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.

RE: Tourist submersible visiting the Titanic is missing Part 2

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 . . .

RE: Tourist submersible visiting the Titanic is missing Part 2

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.

RE: Tourist submersible visiting the Titanic is missing Part 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

RE: Tourist submersible visiting the Titanic is missing Part 2

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.

RE: Tourist submersible visiting the Titanic is missing Part 2

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

RE: Tourist submersible visiting the Titanic is missing Part 2

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

RE: Tourist submersible visiting the Titanic is missing Part 2

What a crap post, dik. Reported.

RE: Tourist submersible visiting the Titanic is missing Part 2

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

RE: Tourist submersible visiting the Titanic is missing Part 2

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.

RE: Tourist submersible visiting the Titanic is missing Part 2

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.

RE: Tourist submersible visiting the Titanic is missing Part 2

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!

RE: Tourist submersible visiting the Titanic is missing Part 2

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."

RE: Tourist submersible visiting the Titanic is missing Part 2

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...

RE: Tourist submersible visiting the Titanic is missing Part 2

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.

RE: Tourist submersible visiting the Titanic is missing Part 2

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.

RE: Tourist submersible visiting the Titanic is missing Part 2

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.

RE: Tourist submersible visiting the Titanic is missing Part 2

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.

RE: Tourist submersible visiting the Titanic is missing Part 2

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.

RE: Tourist submersible visiting the Titanic is missing Part 2

Has ANY of the composite structure been recovered?

Blax

RE: Tourist submersible visiting the Titanic is missing Part 2

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.

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RE: Tourist submersible visiting the Titanic is missing Part 2

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...

RE: Tourist submersible visiting the Titanic is missing Part 2

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.

RE: Tourist submersible visiting the Titanic is missing Part 2

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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RE: Tourist submersible visiting the Titanic is missing Part 2

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.

RE: Tourist submersible visiting the Titanic is missing Part 2

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.

TTFN (ta ta for now)
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RE: Tourist submersible visiting the Titanic is missing Part 2

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.

RE: Tourist submersible visiting the Titanic is missing Part 2

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.

RE: Tourist submersible visiting the Titanic is missing Part 2

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.

TTFN (ta ta for now)
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RE: Tourist submersible visiting the Titanic is missing Part 2

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.

RE: Tourist submersible visiting the Titanic is missing Part 2

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.

RE: Tourist submersible visiting the Titanic is missing Part 2

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.

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

-Dik

RE: Tourist submersible visiting the Titanic is missing Part 2

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

RE: Tourist submersible visiting the Titanic is missing Part 2

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

RE: Tourist submersible visiting the Titanic is missing Part 2

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.

RE: Tourist submersible visiting the Titanic is missing Part 2

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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RE: Tourist submersible visiting the Titanic is missing Part 2

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.

RE: Tourist submersible visiting the Titanic is missing Part 2

2
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.

RE: Tourist submersible visiting the Titanic is missing Part 2

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.

RE: Tourist submersible visiting the Titanic is missing Part 2

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

RE: Tourist submersible visiting the Titanic is missing Part 2

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.

RE: Tourist submersible visiting the Titanic is missing Part 2

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.

RE: Tourist submersible visiting the Titanic is missing Part 2

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...

RE: Tourist submersible visiting the Titanic is missing Part 2

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

RE: Tourist submersible visiting the Titanic is missing Part 2

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.

RE: Tourist submersible visiting the Titanic is missing Part 2

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

RE: Tourist submersible visiting the Titanic is missing Part 2

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

RE: Tourist submersible visiting the Titanic is missing Part 2

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

RE: Tourist submersible visiting the Titanic is missing Part 2

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

RE: Tourist submersible visiting the Titanic is missing Part 2

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

RE: Tourist submersible visiting the Titanic is missing Part 2

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...

RE: Tourist submersible visiting the Titanic is missing Part 2

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.

RE: Tourist submersible visiting the Titanic is missing Part 2

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.

RE: Tourist submersible visiting the Titanic is missing Part 2

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

RE: Tourist submersible visiting the Titanic is missing Part 2

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.

RE: Tourist submersible visiting the Titanic is missing Part 2

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.

RE: Tourist submersible visiting the Titanic is missing Part 2

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

TTFN (ta ta for now)
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RE: Tourist submersible visiting the Titanic is missing Part 2

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?

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

-Dik

RE: Tourist submersible visiting the Titanic is missing Part 2

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.

RE: Tourist submersible visiting the Titanic is missing Part 2

Thanks, Tug...

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

-Dik

RE: Tourist submersible visiting the Titanic is missing Part 2

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.

RE: Tourist submersible visiting the Titanic is missing Part 2

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.

RE: Tourist submersible visiting the Titanic is missing Part 2

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").

RE: Tourist submersible visiting the Titanic is missing Part 2

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.

RE: Tourist submersible visiting the Titanic is missing Part 2

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

RE: Tourist submersible visiting the Titanic is missing Part 2

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.

RE: Tourist submersible visiting the Titanic is missing Part 2

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.

RE: Tourist submersible visiting the Titanic is missing Part 2

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.

RE: Tourist submersible visiting the Titanic is missing Part 2

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

RE: Tourist submersible visiting the Titanic is missing Part 2

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

RE: Tourist submersible visiting the Titanic is missing Part 2

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.

RE: Tourist submersible visiting the Titanic is missing Part 2

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.

RE: Tourist submersible visiting the Titanic is missing Part 2

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.

RE: Tourist submersible visiting the Titanic is missing Part 2

2
TugboatEng

SwinnyGG's comments about yield/ultimate are correct, if a little blunt (a bit like my responses at times bigglasses). 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

RE: Tourist submersible visiting the Titanic is missing Part 2

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.

RE: Tourist submersible visiting the Titanic is missing Part 2

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.

RE: Tourist submersible visiting the Titanic is missing Part 2

"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.

RE: Tourist submersible visiting the Titanic is missing Part 2

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?

RE: Tourist submersible visiting the Titanic is missing Part 2

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.

RE: Tourist submersible visiting the Titanic is missing Part 2

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.

RE: Tourist submersible visiting the Titanic is missing Part 2

"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.


RE: Tourist submersible visiting the Titanic is missing Part 2

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

RE: Tourist submersible visiting the Titanic is missing Part 2

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.

RE: Tourist submersible visiting the Titanic is missing Part 2

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."

TTFN (ta ta for now)
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RE: Tourist submersible visiting the Titanic is missing Part 2

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!

RE: Tourist submersible visiting the Titanic is missing Part 2

"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.

RE: Tourist submersible visiting the Titanic is missing Part 2

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.

TTFN (ta ta for now)
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RE: Tourist submersible visiting the Titanic is missing Part 2

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.

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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RE: Tourist submersible visiting the Titanic is missing Part 2

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

RE: Tourist submersible visiting the Titanic is missing Part 2

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.

RE: Tourist submersible visiting the Titanic is missing Part 2

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.

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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RE: Tourist submersible visiting the Titanic is missing Part 2

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?

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

RE: Tourist submersible visiting the Titanic is missing Part 2

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.

RE: Tourist submersible visiting the Titanic is missing Part 2

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.

RE: Tourist submersible visiting the Titanic is missing Part 2

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.

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

RE: Tourist submersible visiting the Titanic is missing Part 2

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.

RE: Tourist submersible visiting the Titanic is missing Part 2

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

RE: Tourist submersible visiting the Titanic is missing Part 2

Let's face they still get in helicopters.

RE: Tourist submersible visiting the Titanic is missing Part 2

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.

RE: Tourist submersible visiting the Titanic is missing Part 2

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

RE: Tourist submersible visiting the Titanic is missing Part 2

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.

RE: Tourist submersible visiting the Titanic is missing Part 2

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.

RE: Tourist submersible visiting the Titanic is missing Part 2

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?

RE: Tourist submersible visiting the Titanic is missing Part 2

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.

RE: Tourist submersible visiting the Titanic is missing Part 2

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.

RE: Tourist submersible visiting the Titanic is missing Part 2

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.

RE: Tourist submersible visiting the Titanic is missing Part 2

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.

RE: Tourist submersible visiting the Titanic is missing Part 2

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.

TTFN (ta ta for now)
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RE: Tourist submersible visiting the Titanic is missing Part 2

(OP)
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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RE: Tourist submersible visiting the Titanic is missing Part 2

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

RE: Tourist submersible visiting the Titanic is missing Part 2

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 . . .

RE: Tourist submersible visiting the Titanic is missing Part 2

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.

RE: Tourist submersible visiting the Titanic is missing Part 2

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

RE: Tourist submersible visiting the Titanic is missing Part 2

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.

RE: Tourist submersible visiting the Titanic is missing Part 2

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.

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

RE: Tourist submersible visiting the Titanic is missing Part 2

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

RE: Tourist submersible visiting the Titanic is missing Part 2

Fair enough - then it doesn't look like OSHAs policy was strong enough?

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

RE: Tourist submersible visiting the Titanic is missing Part 2

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

RE: Tourist submersible visiting the Titanic is missing Part 2

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.

RE: Tourist submersible visiting the Titanic is missing Part 2

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.

RE: Tourist submersible visiting the Titanic is missing Part 2

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.

RE: Tourist submersible visiting the Titanic is missing Part 2

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.

RE: Tourist submersible visiting the Titanic is missing Part 2

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?

RE: Tourist submersible visiting the Titanic is missing Part 2

I believe they had completed a few successful dives, already with the Titan.

RE: Tourist submersible visiting the Titanic is missing Part 2

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.

RE: Tourist submersible visiting the Titanic is missing Part 2

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

TTFN (ta ta for now)
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RE: Tourist submersible visiting the Titanic is missing Part 2

Does that mean OSHA should have chimed in on the Columbia and Challenger shuttle failures?

RE: Tourist submersible visiting the Titanic is missing Part 2

Astronauts were not paying customers.

RE: Tourist submersible visiting the Titanic is missing Part 2

I'm not aware that OSHA regulates employee safety in international waters, though.

RE: Tourist submersible visiting the Titanic is missing Part 2

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.

RE: Tourist submersible visiting the Titanic is missing Part 2

SOLAS is the international safety at sea organization but not all vessels are subject to SOLAS rules. None of my vessels are.

RE: Tourist submersible visiting the Titanic is missing Part 2

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.

RE: Tourist submersible visiting the Titanic is missing Part 2

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.

RE: Tourist submersible visiting the Titanic is missing Part 2

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.

RE: Tourist submersible visiting the Titanic is missing Part 2

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.

RE: Tourist submersible visiting the Titanic is missing Part 2

A little off topic but I think people should know this. State employees can opt out of social security as well.

RE: Tourist submersible visiting the Titanic is missing Part 2

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

RE: Tourist submersible visiting the Titanic is missing Part 2

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.

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