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Rocket general questions

Rocket general questions

Rocket general questions

(OP)
From today's launch (nice launch, not so nice flight) of SpaceX ...
1) what gas are they venting ? can't think they've venting methane
2) how do they control pressure in the tanks ? do they have a bladder/balloon where they can add/remove gas/liquid (N2 ?)
3) they made a point of filling the header tanks (which would not be used) ... so they intended to dump a tank (small though it may be) full of methane into the Pacific ??
4) when they chill the plumbing and such before loading fuel, I assume they're only passing N2 through the system, and it doesn't hang around long (as it did when they did the cryo testing)

"Hoffen wir mal, dass alles gut geht !"
General Paulus, Nov 1942, outside Stalingrad after the launch of Operation Uranus.

RE: Rocket general questions

If you are referring to the jets coming out the sides of the rocket, I think those were maneuvering thrusters, trying desperately to regain control of the wobble from not all of the engines firing

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: Rocket general questions

RB... I replied in the SLS thread... earlier.

However here are some of my thoughts on what was visible...

The 1st stage had multiple [5 or 6???] engine failures probably leading to loss of control [cork-screwing] and disintegration before staging could occur, ~3:57 into launch. It appears that SpaceX MAY have allowed the fight to proceed to vehicle 'break-up' and did not initiate self-destruct sequence.

I suspect that with one or more engine failures, there were multiple plumes of uncontroled hot gases venting from the base of the 1st stage. These plumes possibly contributed to instability that could not be controlled by engine gimbling.

On launch, it appears that 3-engines were in-op from lift-off... then 1 other went in-op soon after.

At ~+40 seconds 1-more engine went in-op.

At ~+1:25 another engine went in-op. At this time there were no tramp 'plumes'.
Oddly the figure in the lower left corner of the picture showed 5-engine down... but the image of the base showed 6-engines in-op... most in the outer row and very asymmetric.

At ~+1:45 the nominal plume expansion began to show asymmetry irregularities and instability.

At about +1:50 a noticeable roll develops... and soon after the entire vehicle begins to slowly pitch and roll... corkscrew-wise. At this point failure was inevitable.

At 4:14 the camera in the launch control room pans... and Musk is sitting quietly/stoically. A little later he appears annoyed at the clapping.

This 'commentary' just popped-up on You-Tube... https://www.youtube.com/watch?v=vta1rueCMW0

I wonder how many launch failures will come... and how many will be tolerated by the FAA and Texas?

Regards, Wil Taylor
o Trust - But Verify!
o For those who believe, no proof is required; for those who cannot believe, no proof is possible. [variation, Stuart Chase]
o Unfortunately, in science what You 'believe' is irrelevant. ["Orion", HBA forum]
o Only fools and charlatans know everything and understand everything." -Anton Chekhov

RE: Rocket general questions

(OP)
shame on you Will ... linking SLS and SpaceX !

yeah, you could see it unfolding. Nice launch, shame about the flight ?

I still don't get Starship as a lunar lander; what do you mean the door is all the way up there ??
Much prefer the "Space 1999" Eagle ... landing on 4 legs, close to the ground.

"Hoffen wir mal, dass alles gut geht !"
General Paulus, Nov 1942, outside Stalingrad after the launch of Operation Uranus.

RE: Rocket general questions

Thinking about 30-some odd engines starting simultaneously, at north of 1.7 million pounds of thrust, and where does the exhaust flow go? The shock reflection off the flat concrete launch pad some 10 feet or so below the nozzle bells has GOT to cause problems for ignition and flame development across the swath of engines trying to light off. Would be an interesting plume calculation, though likely futile - was the base structure and fairings near the base designed to prevent full throttle rocket plume from travelling back up along the tanks and engine plumbing? Stupid not to use a flame diverter/bucket on the launch pad, as all rocket launches since the Mercury program have used. And yeah, I'd have been annoyed at all the clapping and cheering going on, it would be like cheering a crash at the Indy 500.

RE: Rocket general questions

Quote (I wonder how many launch failures will come...)


You've heard about the Model A and the Model T... What about the Model B through to Model S?

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

-Dik

RE: Rocket general questions

Dik -

In SpaceX's case, they have taken a page from failures (Energiya) rather than proven designs (Apollo, Shuttle, SLS) for heavy booster designs. So it's going from an F150 or whatever back to the Edsel...

And I agree with Wil, so far SpaceX has gotten lucky and not killed anybody (that I know of?). Drop a million pounds of esplody booster on a small African country and watch what happens to Tesla stock prices.

RE: Rocket general questions

Agree... my attempt at humour was not so good...

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

-Dik

RE: Rocket general questions

(OP)
I think that's a bit harsh on SpaceX. Sure they have a bunch of experiments before they figure things out. How many experiments did NASA have in the 60s ?

Ok, so they've taken a different design approach to achieve different goals. Are solid fuel rockets better than liquid fuel ? IMHO, no, each design has pros, and cons. SpaceX is trying to make a highly reusable design ... is that "wrong" ? is staying with expendable rockets the way of the future ? SpaceX has shown a much higher launch cadence than anyone has done before, and much cheaper. is that "bad" ?

To claim that a SpaceX design is several generations behind SLS is, IMHO, ludicrous.

"Drop a million pounds of esplody booster on a small African country and watch what happens to Tesla stock prices." What happened when NASA did this over Texas ?
Range safety is designed expressly so this doesn't happen. By the time StarShip was over Africa the Booster had already been staged, so it was much lighter and higher ... and would probably burn up on descent.

"Hoffen wir mal, dass alles gut geht !"
General Paulus, Nov 1942, outside Stalingrad after the launch of Operation Uranus.

RE: Rocket general questions

Sorry to poke fun at your hero, Rb. I don't dispute most of what you wrote (my 2nd post was mostly in jest), except the following rebuttals

- why did they not replicate the launch pad designs that NASA developed and proved to work over decades? The damage done to their pad, and the likelihood that the launch pad destruction may have (via debris collisions) contributed to their launch failure (pardon me, "unplanned disassembly") speak to a level of hubris that is common to the startup mentality (move fast and break things). Successful and cheap it may be...until somebody gets hurt.
- NASA has range safety officials that aren't on Musk's payroll, and will destroy a rocket safely over the Atlantic, long before it executes two (or three? I lost count) cartwheel rolls. NASA didn't drop a fuel-heavy booster on Texas, get your facts straight.
- Having 30-plus engines spread across the base of the rocket is a novel, unproven (Energiya blew up on first test launch too, and then Russia gave up on it), and tricky configuration, and worth a lot more testing to verify startup characteristics long before doing a full stack launch. I think they did one brief hot fire of the booster? And had engine failures on that test, which would have made a more conservative outfit repeat the test to get the ignition sequence figured out.

"To claim that a SpaceX design is several generations behind SLS is, IMHO, ludicrous."

Ludicrous is exactly what SpaceX strives for, i.e. development speed at all costs. I've spoken to quite a few engineers who worked there, and all of them left because they were afraid of being sucked into a lawsuit deposition. Acceptance of risk ...ah screw it, it's beer 30 on Friday. Good luck to them.

RE: Rocket general questions

A few random thoughts crossed my mind.

I understand the concept of liquid methane + LOX for the crew stage... propellant of convenience on the Red planet for the return. HOWEVER, the first stage/booster will never leave the surely bonds of earth returning softly or 'splashing'. What bothers me is that the immensely successful Falcon 9 and Falcon-Heavy use conventional RP-1 + LOX for the first stages. Introducing a novel propellant into a novel booster design seems sketchy-at-best... especially 'early in development'... one more thing to count as 'experimental'.

Also... any one else notice that the [4] grid fins on the upper last few feet of the booster were deployed on lift-off... not folded/faired back like the Falcons? In every other stationary photo they were folded/faired-back. I wonder if this was deliberate... or was feature intended for extra control due to booster engine failures?

When it became obvious the booster was beginning to cork screw. Why NOT force the stage separation and light-up the crew stage engines... to see if abort was possible in this bizarre circumstance... or find-out what else might happen???

Also... concept of Starship landing tail first on the Moon or Mars... with extendable legs. The dust/debris kicked-up by even reduced-thrust engines might actually damage the engines/bell-expansion chambers, clog injector-plates, etc. These same engines, I presume, are intended for lift-off and return-maneuvering and ultimately soft landing on earth. Sketchy survival with potentially damaged engines... or insulation or aft thrust structure.

NOTE: The Apollo Grumman-LEMs had the ultimately simple/elegant answers to many problem, including, to a degree, CREW SAFETY. Ditch the landing stage with it's potentially damaged engine/bell/weight and have a compact self-contained, undamaged/fully-fueled upper stage return to orbit from the surface or during a wild-crazy landing abort. OH yeah, conveniently, the maneuvering thrusters were all clustered on/stayed-with the upper-stage [4-quadrants]. KISS.

btrueblood... the STARSHIP booster/upper-stage likely disintegrated-over/crashed-into international waters of the Gulf of Mexico... but it is still practically in Texas's backyard... and certainly well within the USA ADIZ. OR perhaps it will come to light that NASA did 'push-the-terminate-button'... but I sincerely doubt it for this private test-launch from private-land. This incident will likely have an exhaustive mishap investigation to come, BEFORE next flight.

Regards, Wil Taylor
o Trust - But Verify!
o For those who believe, no proof is required; for those who cannot believe, no proof is possible. [variation, Stuart Chase]
o Unfortunately, in science what You 'believe' is irrelevant. ["Orion", HBA forum]
o Only fools and charlatans know everything and understand everything." -Anton Chekhov

RE: Rocket general questions

(OP)
"Also... any one else notice that the [4] grid fins on the upper last few feet of the booster were deployed on lift-off... not folded/faired back like the Falcons? In every other stationary photo they were folded/faired-back. I wonder if this was deliberate... or was feature intended for extra control due to booster engine failures?" ... yes, I noticed that. I think they talked about it some time back. I think the idea is less complexity and less weight and more reliability to have the fins permanently deployed. the fuel penalty is less than the mechanism and system required to make them deployable. I believe they are deployable on Falcon rockets.

"Hoffen wir mal, dass alles gut geht !"
General Paulus, Nov 1942, outside Stalingrad after the launch of Operation Uranus.

RE: Rocket general questions

RB... the extended grid fins so far forward have to affect flight characteristics; IE destabilizing.

This analysis by Scott Manely has a ton of 'good' info on the SpaceX Starship Launch...

SpaceX's Massive Rocket Explodes Due to Rapid Unscheduled Digging [launch pad destruction]
https://www.youtube.com/watch?v=w8q24QLXixo

Also... The South Texas locals are from 'overjoyed' about the 'variety and intensity of the debris'...
SpaceX celebrated Starship's 1st launch. Some locals called it 'truly terrifying'
https://www.space.com/spacex-starship-launch-debri...?

Regards, Wil Taylor
o Trust - But Verify!
o For those who believe, no proof is required; for those who cannot believe, no proof is possible. [variation, Stuart Chase]
o Unfortunately, in science what You 'believe' is irrelevant. ["Orion", HBA forum]
o Only fools and charlatans know everything and understand everything." -Anton Chekhov

RE: Rocket general questions

(OP)
yes, I'm aware of Scott's YT channel.

Whether they are destabliing or not I was answering the question "why?" as best I can think of. I'm "sure" they've accounted for these aero effects. The fins are steerable.

But ... this was the first time these fins flew ... and look what happened ... it was reasonably stable when sub-sonic, but no so much when supersonic ?? I'm sure they guys with the data can figure this out ...
(yes, I like ellipses ...)

"Hoffen wir mal, dass alles gut geht !"
General Paulus, Nov 1942, outside Stalingrad after the launch of Operation Uranus.

RE: Rocket general questions

The grid fins do not fold down on super heavy, that is part of the design, they do twist though.
The grid fins are also support structure for the tower to catch, lift, set
and hold while at the launch stand. My guess adding a pivot weighs more than the performance loss
of having them in the slip stream, and that pivot would need to be strong enough for those other uses.

The use of methane allows the use of full flow staged combustion cycle, the only cycle more efficient is the expander cycle which has a hard limit on size and only works best on H2. RP1 will soot up any partial combustion in a cycle.

side benefit, Methane is significantly lower cost that H2 or RP1

Hydrae

RE: Rocket general questions

(OP)
ok, nice discussion, but back to the original questions ...

what gas are they venting ? there was much "talk" about the liquids boiling off which would imply methane and O2 are being vented. But I can't believe they'd vent methane (or any other fuel) ... so ...

how do they pressurise the tanks ? Do they use a bladder, by which they can control the volume (and therefore pressure) ? Then they could be venting this inert (N2) gas.

"Hoffen wir mal, dass alles gut geht !"
General Paulus, Nov 1942, outside Stalingrad after the launch of Operation Uranus.

RE: Rocket general questions

https://www.popsci.com/technology/spacex-starship-...

... 'last words'...
Update 4/25/23: The Federal Aviation Administration (FAA) confirmed to CNBC on Monday afternoon that it has grounded the company’s Starship Super Heavy launch program pending results of the “mishap investigation” which was “triggered by debris entering adjacent properties.”

Regards, Wil Taylor
o Trust - But Verify!
o For those who believe, no proof is required; for those who cannot believe, no proof is possible. [variation, Stuart Chase]
o Unfortunately, in science what You 'believe' is irrelevant. ["Orion", HBA forum]
o Only fools and charlatans know everything and understand everything." -Anton Chekhov

RE: Rocket general questions

SpaceX Starship launch under FAA investigation after raining potentially hazardous debris on homes and beaches
https://www.space.com/spacex-starship-faa-mishap-i...

"The FAA will oversee the mishap investigation of the Starship/Super Heavy test mission," FAA officials wrote.
SpaceX's Starship has been grounded by the U.S. government following claims that the rocket's explosive first launch spread plumes of potentially hazardous debris over homes and the habitats of endangered animals.
The Federal Aviation Administration (FAA) — the U.S. civil aviation regulator — has stopped SpaceX from conducting any further launches until it has concluded a "mishap investigation" into Starship's April 20 test launch. The massive rocket’s dramatic flight began by punching a crater into the concrete beneath the launchpad and ended when the giant rocket exploded in mid-air around 4 minutes later.

... ...
SpaceX...


Regards, Wil Taylor
o Trust - But Verify!
o For those who believe, no proof is required; for those who cannot believe, no proof is possible. [variation, Stuart Chase]
o Unfortunately, in science what You 'believe' is irrelevant. ["Orion", HBA forum]
o Only fools and charlatans know everything and understand everything." -Anton Chekhov

RE: Rocket general questions

(OP)
surely this is all very standard procedures after such a "mishap" ?
and not something exceptional ...

"Hoffen wir mal, dass alles gut geht !"
General Paulus, Nov 1942, outside Stalingrad after the launch of Operation Uranus.

RE: Rocket general questions

Pretty sure Musk hadn't planned on a 'real mishap investigation'.

Suspect He simply wanted everyone to 'just leave SpaceX alone to do-its thing and everything will work-out just fine'... with the most massive launch vehicle ever made by man.

Regards, Wil Taylor
o Trust - But Verify!
o For those who believe, no proof is required; for those who cannot believe, no proof is possible. [variation, Stuart Chase]
o Unfortunately, in science what You 'believe' is irrelevant. ["Orion", HBA forum]
o Only fools and charlatans know everything and understand everything." -Anton Chekhov

RE: Rocket general questions

(OP)
be fair ... he's played along with FAA licensing his launch, he's had accident investigations in the past. This is "just" another investigation ... which is something he'd do himself, to fix the problem.

"Hoffen wir mal, dass alles gut geht !"
General Paulus, Nov 1942, outside Stalingrad after the launch of Operation Uranus.

RE: Rocket general questions

Falcon 9, Falcon-Heavy flight mishap investigations from launch pads designed for safety, re-usability and no-where-near local populations. In these cases, launch/flight analysis investigation anomalies involve ONLY the launch vehicle/payload.

In Musk's case... it might be wise to remember the following...

"Success is a lousy teacher. It seduces smart people into thinking they can't lose." --Bill Gates, Microsoft Corp. co-founder, philanthropist



Regards, Wil Taylor
o Trust - But Verify!
o For those who believe, no proof is required; for those who cannot believe, no proof is possible. [variation, Stuart Chase]
o Unfortunately, in science what You 'believe' is irrelevant. ["Orion", HBA forum]
o Only fools and charlatans know everything and understand everything." -Anton Chekhov

RE: Rocket general questions

(OP)
is that an example of "the blind leading the blind" ?

why would anyone (particularly an engineer) like that Musk's reaction to the first launch would be "damnit, let's do it again (without any investigation)"

He wants to get the rocket to complete the launch (more than most people). He knows and has demonstrated that his team knows and that he understands his team that the reason for the "unscheduled rapid disassembly" was not the desired outcome and will learn as much as they (and NASA and FAA) can about what caused it (as in any aviation accident) and how to stop it happening again.

But, please, ... venting gases anyone ??

"Hoffen wir mal, dass alles gut geht !"
General Paulus, Nov 1942, outside Stalingrad after the launch of Operation Uranus.

RE: Rocket general questions

RB... I surrender... This is my last posting here...

The Military and NACA/NASA did early test-learn-test-learn-test-learn- on the first IRBM/ICBM missiles... and wound-up with protocol and insight to design Saturn V... which never had a true failure.

OK... so WHY would SpaceX launch Starship from a fixed platform over concrete... without a suitable flame trench and water suppression [water scarce?]... so close to a populated area? OH yes... and lets skip the static full duration firing tests... and just learn-from-tests about the launch pad/area in 'real-time'.

I'm pretty sure that Musk wishes that the surrounding homes/community would just be condemned by Texas... and the land turned-over to SpaceX... That'll take care of the problem!!!

Regards, Wil Taylor
o Trust - But Verify!
o For those who believe, no proof is required; for those who cannot believe, no proof is possible. [variation, Stuart Chase]
o Unfortunately, in science what You 'believe' is irrelevant. ["Orion", HBA forum]
o Only fools and charlatans know everything and understand everything." -Anton Chekhov

RE: Rocket general questions

"so WHY would SpaceX launch Starship from a fixed platform over concrete... without a suitable flame trench and water suppression"

I have seen a Musk fanboi claiming that it was because any launch from another planet would be from an unprepared site. Hmm.

Cheers

Greg Locock


New here? Try reading these, they might help FAQ731-376: Eng-Tips.com Forum Policies http://eng-tips.com/market.cfm?

RE: Rocket general questions

(OP)
will, "and wound-up with protocol and insight to design Saturn V... which never had a true failure" ... really ? except for the first one, eh ? but yes, NASA were laerning things, just as SpaceX is learning things, because they're choosing to do things differently ... prioritising other aspects of the design. I'm no "Musk fanboi", as I've previously posted I thought landing a rocket was farcical ... and the first couple of attempts supported this. But he persevered and now 1) has a system with a launch cadence NASA can't dream of, and 2) is the trailblaser for all the "johnny-come-lately"s who are also landing rockets.

I'm not supporting his decision about the landing pad etc (always wondered about the fuel farm being so close to the launch site). I have no doubt that he'll repair the launch site and we'll be seeing SpaceX rockets launching there in the future.

As for the surrounding houses ... I wonder how Cape Canaveral was set up ... maybe by the US Government buying out property owners ?? and yes, I'm sure he wishes that that PITA would just go away ... but he's no different to anyone else.

but, please, anyone ... venting gases ?

"Hoffen wir mal, dass alles gut geht !"
General Paulus, Nov 1942, outside Stalingrad after the launch of Operation Uranus.

RE: Rocket general questions

(OP)
final word (I hope but doubt) about the launch pad concrete ... some engineer decided what they had was at least "adequate" given some modelling of the launch pressures.

"Hoffen wir mal, dass alles gut geht !"
General Paulus, Nov 1942, outside Stalingrad after the launch of Operation Uranus.

RE: Rocket general questions

"There is a name for those who suppose that doing the same thing will produce different results. That name is ‘Idiot’.” -Albert Einstein

Regards, Wil Taylor
o Trust - But Verify!
o For those who believe, no proof is required; for those who cannot believe, no proof is possible. [variation, Stuart Chase]
o Unfortunately, in science what You 'believe' is irrelevant. ["Orion", HBA forum]
o Only fools and charlatans know everything and understand everything." -Anton Chekhov

RE: Rocket general questions

Becker traced the original back to Rita Mae Brown, the mystery novelist. In her 1983 book "Sudden Death," she attributes the quote to a fictional "Jane Fulton," writing, "Unfortunately, Susan didn’t remember what Jane Fulton once said. 'Insanity is doing the same thing over and over again, but expecting different results.'"

RE: Rocket general questions

RB... question to You...?

Quote (will, "and wound-up with protocol and insight to design Saturn V... which never had a true failure" ... really ? except for the first one, eh ?)


I went thru all Saturn V launches I'm aware of... and there were NO launch failures... a few serious problems, heck-Yes... catastrophic failures, NO.

I cannot count the Apollo 1 CSM interior fire... during dress rehearsal... a launch failure.

Of course, The Space Shuttle program was a completely different 'hot mess'...

Regards, Wil Taylor
o Trust - But Verify!
o For those who believe, no proof is required; for those who cannot believe, no proof is possible. [variation, Stuart Chase]
o Unfortunately, in science what You 'believe' is irrelevant. ["Orion", HBA forum]
o Only fools and charlatans know everything and understand everything." -Anton Chekhov

RE: Rocket general questions

(OP)
without intending to be callous about it ... NASA has killed more people than SpaceX. Rocketry is a hard business and lessons are learnt painfully.

Should we only use the design formulae that NASA learnt ? Is it wrong for SpaceX to try and develop new solutions, that allow us to do amazing new things.

I'm not saying SpaceX is perfect, but they are trying to do new things and they have succeeded (c'mon, even the most grudging critic must see that).
Have they made some bad decisions ? sure, the pad design is being revisited. Sure, some people will say "told you so", and they'd be right.
But some engineer and SpaceX management thought what they were doing had at least a chance of working, or of working with an acceptable amount of rework.
Ok, they've learnt and are doing a redesign. Ok, you can say "it was obvious (given the power of the rocket)" ... I contend that others thought it had a shot, based on some analysis and not on Elon saying "make it so" (or at least I hope not).

But seriously guys, does no one know what gases are venting ?

"Hoffen wir mal, dass alles gut geht !"
General Paulus, Nov 1942, outside Stalingrad after the launch of Operation Uranus.

RE: Rocket general questions

Up-to now, SpaceX has Launched from NASA/DoD launch-sites where superior launch services were established... Duhhh... including flame trenches and water suppression, widely spaced support facilities, etc.

I don't think SpaceX even launched any of the Falcon series from Boca Chica TX... to establish lessons-learned.

Also... let us not forget that NASA accepted SpaceX's moon lander bid 16 April 2021... after the long/short bidding process during the Trump administration. Hmmmmmm.

Also... On the aspect of man-rated launchers.
NASA/DoD has learned hard/painful lesson from all all aspects of space flight. The 'race to the moon' in the 1960s had really smart seasoned staff pressing forward at the speed-of-heat to meet 1969-man-on-the-moon challenges... and HAD to take steps backward after catastrophes.

For SpaceX... NASA/FAA MANDATED a significant level of safety during launch-fight-stay-duration and re-entry... systems and testing... to ensure highest probability of human survival to-from-earth orbit. SpaceX met that challenge and... also... the 'hat-trick' technology of landing boosters for re-use. I wonder how this program would have 'worked-out' if feet hadn't been put to the fire for safety?

Going back to Boca Chica... Every element of that launch site... and the Starship Program... looks like a throw-back to the 1950's... NOT a smart/savvy extension of the Falcon 1/9/heavy... lessons learned.

Like I said prior... in the interests of progress, expect Texas to condemn/buy-out [at ~10-Cents on the dollar] the surrounding 10-to-20-+ miles-radius... homes and villages/communities... possibly to the Mexican Border. That will solve the problem of locals whining about launch damage and eco-system destruction and all the other disruptions that SpaceX has brought to this area. Besides "it will mostly affect Hispanics who could move anywhere and live just as cheaply". YES I just said that.

Regards, Wil Taylor
o Trust - But Verify!
o For those who believe, no proof is required; for those who cannot believe, no proof is possible. [variation, Stuart Chase]
o Unfortunately, in science what You 'believe' is irrelevant. ["Orion", HBA forum]
o Only fools and charlatans know everything and understand everything." -Anton Chekhov

RE: Rocket general questions

"Should we only use the design formulae that NASA learnt ? Is it wrong for SpaceX to try and develop new solutions, that allow us to do amazing new things."

Of course not...but one should proceed with caution when exploring new territory, especially with regard to passerby and surrounding communities. And not ignore the results from your own prior tests - engine out failures in static firings being ignored is a problem with management hubris, much like NASA launching the shuttle boosters in low temperatures.

What gases are venting? Well, it's either oxygen or methane...there would be little to no liquid nitrogen left aboard after launch, no need for it once the rockets are lit. There may be some helium tanks aboard for pressurizing attitude control thrusters, but that is unlikely to create huge visible condensation clouds if it was venting. My guess is it's LOX venting, since the plume(s) does/did not catch fire. Whatever was venting was doing so in fairly voluminous quantities for a long period of time, and led to the engines getting starved of propellant (low velocity and altitude) well before the expected separation point, Manley points it out in his video (I thought)? Seems like the same debris impacts that knocked out engines at launch may also have poked some holes in the tank(s)? Or possibly the engine out failures resulted in enough torque on the missile to strain and rupture the tank walls at some point (unlikely, they should have been stressed for that). I assume the FAA will be conducting a failure investigation, and more details may become available as time goes by.

I have to agree with Wil, and I expect the decisions made for Boca Chica were as much about cost cutting and schedule acceleration as they were about anything else. The idea of using the booster (not the starship, though even that vehicle's weight and size make it iffy) for landings and ascents from the moon or Mars is a bit crazy, why drag all that dead weight along. Maybe it is possible, but will need to be proven. The Mars and lunar lander engines had a lot of design work in plume analysis to reduce scour of the (then unknown but presumed very soft) lunar/Martian soils.

RE: Rocket general questions

(OP)
ok, back to the topic.

For some YT discussion I've had, I think they vent O2 (still a small flame risk ?) but the fuel vent is recovered (and not vent to atmosphere).

Still interested in how they pressurise the tanks (well, control the pressure in the tanks) and how do they separate the N2 used to chill the tank and plumbing) from the O2 (or fuel) ?

"Hoffen wir mal, dass alles gut geht !"
General Paulus, Nov 1942, outside Stalingrad after the launch of Operation Uranus.

RE: Rocket general questions

Somewhere I read a post or video (more Scott Manley?) that claims the venting seen around the time the vehicle goes into its death spiral, and continues for some 40-50 seconds until it explodes...WAS the rupturing of the fuel and oxidizer tanks by the flight safety abort system. The claim is that the tank pressurization took that long to decay until the tanks lost enough structural rigidity to fully collapse.

RE: Rocket general questions

(OP)
yeah, I wasn't meaning about the specific SpaceX launch but rockets in general.

"Hoffen wir mal, dass alles gut geht !"
General Paulus, Nov 1942, outside Stalingrad after the launch of Operation Uranus.

RE: Rocket general questions

Fuel venting is an issue only for cryogenics; they vented the shuttle (H2) prior to launch to a flare tower near the pad, then afterwards yes the fuel "vents" to the turbopump inlet. I would assume similar happens for methane...but SpaceX does not publish a lot of stuff. Shuttle and SLS tanks get helium pressurization, again dunno SpaceX. Filling lox tanks is done by chilling with LN2 first. LN2 eventually boils off, as it boils at lower temp than LOX it leaves the lox behind. Pressure is controlled by venting regulator spilling overboard, I think we see that on SLS, Shuttle, and possibly starship launches - essentially residual LN2 boiling off?

RE: Rocket general questions

(OP)
yes, thx ! yes RT liquid fuels don't need a vent (though there probably is some off-gassing). And yes, the clouds of vented gas are not fuel vapour (as obviously not !). So fuel vapours (like on SpaceX) are AIUI recycled through the quick disconnect.

ok, but what happens to the LN2 (I assume) used to chill the tank and plumbing or do they chill with LO2 ? But you wouldn't chill the fuel tank with LO2 !!

And how do they control the pressure in the tanks ? I mean, I see them filling these vast tanks (I imagine they fill from the bottom ?) Is the tank prefilled with LN2 ? Is there no mixing ?? (because the fuel is heavier than the LN2 ?)

"Hoffen wir mal, dass alles gut geht !"
General Paulus, Nov 1942, outside Stalingrad after the launch of Operation Uranus.

RE: Rocket general questions

Rb1957 it is unclear what venting that you are referring to. The Raptor engines have a second combustion chamber to drive the turbo pumps for the main engine. The exhaust from this may be what you are referring to.
https://youtu.be/LbH1ZDImaI8

RE: Rocket general questions

(OP)
I'm talking about the clouds that surround the rocket on the pad, prior to launch. But I think I've "sussed" that ... O2 is vented overboard and fuel vapour is recovered.

"Hoffen wir mal, dass alles gut geht !"
General Paulus, Nov 1942, outside Stalingrad after the launch of Operation Uranus.

RE: Rocket general questions

I've not spent a lot of time looking at how the flight tanks are filled, but yes, you would probably dump LN2 into the tank and let it boil off through a regulator/pressure control valve. Eventually, when temperatures are low enough, you start pumping in LOX, and taper back on LN2. The lines and storage tanks for LOX likely have a shield layer through which more LN2 can be pumped to keep them cold, but I doubt flight tanks have cooling jackets like that. So...most of the vapor you see on the pad is LN2 boiling off, along with some oxygen as filling progresses. I think LN2 mixes with LOX, but the LN2 again evaporates/boils off at a lower temperature, leaving LOX behind.

When I was a rocket engineer, testing with H2/LOX - we chilled a jacketed tank with LN2 (through external jacket and also by trickling LN2 into the internal tank volume - this initially came through as gaseous N2, which kept the tank purged and dry. After several hours, monitoring tank wall temperature and internal tank temp - when temperature was low enough, we closed the LN2 purge trickling into the tank, and opened a valve and trickled in gaseous oxygen (LN2 jacket flow was maintained throughout) through a jacketed line, so it came into the tank fairly cold already. The tank being at LN2 boiling point would condense some/most of the incoming GOX. The residual LN2 in the tank would boil off pretty quickly. The oxygen would vent - and eventually this would start to spit blobs of LOX, which was how we knew we had a full tank. When ready to fire, we would dial up the pressure on the vent regulator (never cap a bottle of LOX, bad things can happen), and open a helium pressurization valve. Even with all that, it took a long run to finally get liquid oxygen down the pipe, through the injector dome, and into the combustion chamber - we were not running full SSME flow but just testing single injectors.

RE: Rocket general questions

Btrueblood... You are a true 'steely-eyed missileman'.

Regards, Wil Taylor
o Trust - But Verify!
o For those who believe, no proof is required; for those who cannot believe, no proof is possible. [variation, Stuart Chase]
o Unfortunately, in science what You 'believe' is irrelevant. ["Orion", HBA forum]
o Only fools and charlatans know everything and understand everything." -Anton Chekhov

RE: Rocket general questions

Mmm...no, I was a lilly-livered missile man (LOL), then left for more civil pursuits after a decade or so. Lily livered: I preferred to be in a bunker somewhere well back from the business end of the motor doing calculations. Well, actually that's not really true, I just told the wife that so she wouldn't worry (but I doubt she bought that, she being a steely-eyed missile woman working in the stress analysis group). I do have a collection of...rapidly disassembled...test hardware from back in the day. The testing I mentioned before - on one occasion I had to walk back into the bunker to reset some optics that the mechanic had bumped. While doing that I noticed a jacketed LOX line was dripping from a Swagelock connector that joined the central (LOX) connection (a separate loop of tubing joined the outer LN2 jackets). I only discovered it because it was very quiet in there, and I could hear the "pop" as drops of LOX hit the concrete floor in the bunker. Concrete that had probably been there since WW1, and seen a lot of oil and fuel leaks over the decades. The pop sound was the LOX igniting and exploding some of that oil. I told the mechanic when I went back through the blast doors, and he went out and tightened the fitting with a pair of wrenches, and then we went ahead and ran our tests. Nobody died, but I did raise an eyebrow at him.

RE: Rocket general questions

BTW... did I not see any lightning strike/diverter towers around the Starship Launch pad?

Regards, Wil Taylor
o Trust - But Verify!
o For those who believe, no proof is required; for those who cannot believe, no proof is possible. [variation, Stuart Chase]
o Unfortunately, in science what You 'believe' is irrelevant. ["Orion", HBA forum]
o Only fools and charlatans know everything and understand everything." -Anton Chekhov

RE: Rocket general questions

(OP)
thx Jennifer (you've been active today ... just joined up ?)

Thx, yes I figured they weren't venting fuel ... there'd be a "rapid disassembly" if they did !

Ok, so they chill the system with LN2 which boils away ?

How do they control the tank pressure ? I mean the propellants are liquid (yes?)but also boiling off vapour (no?) which would need to be vented ?
And how do they keep the propellent separated from any pressurising gas ?

"Hoffen wir mal, dass alles gut geht !"
General Paulus, Nov 1942, outside Stalingrad after the launch of Operation Uranus.

RE: Rocket general questions

OH, GREAT. SpaceX is cobbling together steel protective plate(s) to protect another launch-pad and concrete foundation. It does NOT seem to be an exhaust-blast-deflector/channel system common to professional launch pads.

I guess fake-it-till-you-make-it is Starship launch crew motto.

I wonder what unintended consequences are coming with the next Boca Chica launch, due to this pad modification...?

from what I can tell the pad sustains ~7+ seconds of rocket engine thrust-blast as engines come-on line... and the about +15 seconds more [diminishing] as the vehicle clears the tower.

I wonder what the pad static/dynamic pressures, thermal-flux and sonic-decibels are during this period. The numbers seem unimaginable.

Regards, Wil Taylor
o Trust - But Verify!
o For those who believe, no proof is required; for those who cannot believe, no proof is possible. [variation, Stuart Chase]
o Unfortunately, in science what You 'believe' is irrelevant. ["Orion", HBA forum]
o Only fools and charlatans know everything and understand everything." -Anton Chekhov

RE: Rocket general questions

(OP)
I have to agree with you Will. It looks like bad solution ... to have the exhaust impact on a flat plate. "All" other pads deflect the exhaust to the horizontal. And I don't see know those water jets will survive against the rocket exhaust. I reckon we'll see just so much molten slag where the plates used to be.

But I don't see this as "fake it till you make it". He has a lot of smart guys (non gender specific) working with him. I'm sure they've done some numbers and convinced themselves it'll work. After the next test we'll know.

I mean, who thought landing rockets was either possible or a good idea ? And now he's shown it can be done nearly everyone ('cept for SLS) is doing it.

"Hoffen wir mal, dass alles gut geht !"
General Paulus, Nov 1942, outside Stalingrad after the launch of Operation Uranus.

RE: Rocket general questions

rb...

Quote (I mean, who thought landing rockets was either possible or a good idea ? And now he's shown it can be done nearly everyone ('cept for SLS) is doing it.)


EXCEPT... SpaceX did proof of concept testing with Falcon booster stages in the Texas desert... to get a grip on the physics and all the unknowns... and worked with the proven [then expended] Falcon9 boosters during real-world launches for learning how to land. However, each of these missions was FROM real LAUNCH PADS AND INSTRUMENTED RANGES... under strict NASA and FAA and DoD oversight.

ALSO, NOTE... NASA is now hedging it's bets by funding development of the Blue Origin Lunar lander designs for SLS.

Regards, Wil Taylor
o Trust - But Verify!
o For those who believe, no proof is required; for those who cannot believe, no proof is possible. [variation, Stuart Chase]
o Unfortunately, in science what You 'believe' is irrelevant. ["Orion", HBA forum]
o Only fools and charlatans know everything and understand everything." -Anton Chekhov

RE: Rocket general questions

I am quite impressed with the Falcon landing and engine re-use (though the landing on rockets has been done before for the lunar and Mars landers). Cleaning up engines and turbopumps that have previously run on kerosene (or RP-1) is pretty messy - fuel used in the cooling passages can coke and form deposits; fuel burned in the turbine drives can soot up the turbine blades (generally the turbine drive is fuel-rich to moderate temperatures). Though, not sure if the Raptor engines are using LOX as coolant like the Russians did?

RE: Rocket general questions

(OP)
"quite impressed" ... damn ! this is a tough crowd !

it was IMHO fricking awesome ! (particularly after a couple of failures)

"Hoffen wir mal, dass alles gut geht !"
General Paulus, Nov 1942, outside Stalingrad after the launch of Operation Uranus.

RE: Rocket general questions

Blue Origin Wins Contract For Second Lunar Lander
https://www.avweb.com/aviation-news/286327/

Regards, Wil Taylor
o Trust - But Verify!
o For those who believe, no proof is required; for those who cannot believe, no proof is possible. [variation, Stuart Chase]
o Unfortunately, in science what You 'believe' is irrelevant. ["Orion", HBA forum]
o Only fools and charlatans know everything and understand everything." -Anton Chekhov

RE: Rocket general questions

I'm still not sure the SpaceX Starship is a viable lunar lander - though if they can throttle the engines to 1/7 of their rated thrust, then maybe they won't scour a pit large enough to bury the lander into? The longer landing legs and more dispersed (larger nozzles) thrust pattern makes it look more "fit for the mission". But I'm just armchair quarterbacking. Glad to know they got funding for more than just one design/contractor.

RE: Rocket general questions

(OP)
don't forget they can bleed off a lot of their velocity somewhat above the moon's surface, and over the last 100ft or so may only have <10 fps to worry about.

and also final descent on only 1 engine ?

"Hoffen wir mal, dass alles gut geht !"
General Paulus, Nov 1942, outside Stalingrad after the launch of Operation Uranus.

RE: Rocket general questions

(OP)
personally I still advocate for the Space 1999 Eagle lander.

"Hoffen wir mal, dass alles gut geht !"
General Paulus, Nov 1942, outside Stalingrad after the launch of Operation Uranus.

RE: Rocket general questions

Quote:

But I don't see this as "fake it till you make it". He has a lot of smart guys (non gender specific) working with him. I'm sure they've done some numbers and convinced themselves it'll work. After the next test we'll know.

I'd worry that this is the same group that ostensibly gave the OK to use the launch pad that got thrashed by the last launch.

Quote:

personally I still advocate for the Space 1999 Eagle lander.

I'd second that winky smile

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: Rocket general questions

IR... a thick steel plate 90-deg to the rocket blast could possibly reflect 'sonic pulses' back to the engines, even with water deluge... As opposed to [one or more] canted steel deflector plates, to blast exhaust and sonics sideways.

All-to-often I seen the law of unintended consequences disrupt the pathway to success.

Regards, Wil Taylor
o Trust - But Verify!
o For those who believe, no proof is required; for those who cannot believe, no proof is possible. [variation, Stuart Chase]
o Unfortunately, in science what You 'believe' is irrelevant. ["Orion", HBA forum]
o Only fools and charlatans know everything and understand everything." -Anton Chekhov

RE: Rocket general questions

Ditto what Wil said, and I've said previously - 30 plus engines igniting and firing onto a 90-degree steel (or previously concrete) platform not very far away is going to create a very noisy environment directly below the engines, which are trying to get the flame lit (and the nozzles are still sub-sonic, so that reflected noise is getting to the combustion chamber). It's a recipe for not getting all the fires lit, and potentially starting fires and/or explosions in the aft structure, due to unburnt propellant gases travelling back up inside the heat shielding.

RE: Rocket general questions

I don't see how a significant reflected noise front can penetrate the flame front exiting the engines at several kilometers per second. Anything will be quickly forced sideward and out across the ground. I'm not espousing the design SpaceX has chosen, but I'm willing to wait and see what happens during the next launch. There is a lot of complex physics going on and SpaceX engineers seem determined that this design is sound.

Brad Waybright

The more you know, the more you know you don't know.

RE: Rocket general questions

"I don't see how a significant reflected noise front can penetrate the flame front exiting the engines at several kilometers per second."

Watch some slow motion film of the shuttle main engine ignition sequence, and look at the swirling flow evident in the nozzle bells at the early moments of ignition. Basic physics: until the engine is ignited and running at a significant fraction of full rated thrust, the nozzle is NOT choked, and the flow exiting the nozzle is sub-sonic, and shock/blast waves can and do propagate upstream to the injector face. Those shocks can mess with the flow of the two propellants into the combustion chamber, and blow out the flame of the ignitors and/or cause mixture ratio excursions that can melt the chamber liner and/or push ignition flames back into the LOX dome where the metal of the injector can light off...basically lots of stuff happens during main engine ignition sequencing. NASA/Rocketdyne did dozens of ignition tests to get the sequence correct (timing of valve openings, etc.), with a lot of the first ones ending in molten/destroyed engines and hardware. These were tests done in proper flame-bucket and water deluge type thrust stands, in single engine and multi engine arrays.

"Anything will be quickly forced sideward and out across the ground."

So you did the plume analysis already? There's a lot of empty space between those 31 motors, and not much space between the motors and that big flat plate; there is no diverter bucket to turn the flow and you see on the last launch the result - a huge swirling cloud of dust and debris that completely obscures the engines for several seconds until the rocket lifts off, and several engines are "out", either not igniting or being shutdown automatically for having "excursions" like those early SSME test. I'm saying it's not an easy analysis, and it's obvious that they arm-waved it on the first go. I'm willing to bet we will see another launch with engines "out" at, or shortly after, liftoff.

"I'm willing to wait and see what happens during the next launch. There is a lot of complex physics going on and SpaceX engineers seem determined that this design is sound."

I'm wiling to wait and see too, 'cause it's not my circus nor my monkeys. I hope you are right, and they have fixed all the issues - but it doesn't look that way to me, and I used to do that job for a living. It smacks to me of hubris and a "damn the torpedos" mentality that can be dangerous. Luckily nobody has been hurt (yet) and it's just Elon's money not mine.

RE: Rocket general questions

it was IMHO fricking awesome ! (particularly after a couple of failures)

It's impressive. Again, the science was done already by earlier engineers, SpaceX just did it with their booster stage, which is a neat concept making them reusable. Awesome was the Apollo lunar lander that did it on the first try (and all the subsequent tries), with much cruder automation (and a manual pilot override on the first one), or the Mariner missions that similarly did it on the first and second tries, fully automated, on a different planet. Granted, NASA didn't have a way to film the landing for us, and they've had some screwups since then...but that doesn't negate the awesomeness of those original landings.

RE: Rocket general questions

(OP)
yes, on the scale of awesomeness not much will beat the Apollo 11 landing

"Hoffen wir mal, dass alles gut geht !"
General Paulus, Nov 1942, outside Stalingrad after the launch of Operation Uranus.

RE: Rocket general questions

This video is a look into the beehive that is SpaceX, Boca Chica... Normally this rapid pace would have to indicate corners cut. Hmmm, yep...

I wonder where the $$$$$$$$$$$$$s are coming from... and how deep the pockets are?

With all this activity, I'll bet a paycheck that the local population living around the launch site has a front-seat view of the end to their community. Progress???

This guy isn't Scott Manely... but definitely enthusiastic and

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

Regards, Wil Taylor
o Trust - But Verify!
o For those who believe, no proof is required; for those who cannot believe, no proof is possible. [variation, Stuart Chase]
o Unfortunately, in science what You 'believe' is irrelevant. ["Orion", HBA forum]
o Only fools and charlatans know everything and understand everything." -Anton Chekhov

RE: Rocket general questions

Quote (btrueblood)

So you did the plume analysis already?
Or you could just say "I disagree because...."

Brad Waybright

The more you know, the more you know you don't know.

RE: Rocket general questions

200th SpaceX Booster landing at Vandenberg AFB. Easy-peasy...

https://www.space.com/spacex-200th-rocket-landing-...

Hmmmmm... looked like one-or-two of the landing legs got 'hung-up' temporarily... and finally deployed/locked... after the other legs were 'down/locked... 'just-in-time'... and somewhat out-of-sync with landing commentary.

Regards, Wil Taylor
o Trust - But Verify!
o For those who believe, no proof is required; for those who cannot believe, no proof is possible. [variation, Stuart Chase]
o Unfortunately, in science what You 'believe' is irrelevant. ["Orion", HBA forum]
o Only fools and charlatans know everything and understand everything." -Anton Chekhov

RE: Rocket general questions

Tonight I am recording [2] PBS NOVA shows... Should be exceptional NOVA episodes... well worth the 2-hours of my time... and related to this thread...

Back to the Moon

Rise of the Rockets

Regards, Wil Taylor
o Trust - But Verify!
o For those who believe, no proof is required; for those who cannot believe, no proof is possible. [variation, Stuart Chase]
o Unfortunately, in science what You 'believe' is irrelevant. ["Orion", HBA forum]
o Only fools and charlatans know everything and understand everything." -Anton Chekhov

RE: Rocket general questions

Quote (WKT)

Hmmmmm... looked like one-or-two of the landing legs got 'hung-up' temporarily... and finally deployed/locked... after the other legs were 'down/locked... 'just-in-time'... and somewhat out-of-sync with landing commentary.

If these legs are hydraulically deployed by a single pump the fluid will flow to whichever moves the most freely. It works a lot like an open differential in a car on a slippery surface. At least when the slippery leg reaches it's stop the fluid will start flowing to the next and keep things moving.

The key here is knowing the volume of fluid required to extend all 4 legs. The pump needs to supply this fluid within the required time. Regardless of how the legs respond individually, once that volume of fluid is pumped all legs will be extended.

RE: Rocket general questions

And for fun...

Videos of the Delta Clipper vertical launch, vertical land demonstrator ~1990s

https://youtube.com/shorts/cDTJ3J8R_wk

https://youtube.com/shorts/8Tmi8eI3WaE

Regards, Wil Taylor
o Trust - But Verify!
o For those who believe, no proof is required; for those who cannot believe, no proof is possible. [variation, Stuart Chase]
o Unfortunately, in science what You 'believe' is irrelevant. ["Orion", HBA forum]
o Only fools and charlatans know everything and understand everything." -Anton Chekhov

RE: Rocket general questions

Interesting article...

NASA offers details on commercial space capabilities agreements
https://spacenews.com/nasa-offers-details-on-comme...

Wealth of NASA knowledge, lessons-learned, etc is open for contractor access... based on individual agreements...
NASA selected seven companies June 15 for its Collaborations for Commercial Space Capabilities-2 (CCSC-2) initiative.
https://spacenews.com/nasa-agreements-to-support-w...

Knowledge/experience = intangible power and cost avoidance...


Regards, Wil Taylor
o Trust - But Verify!
o For those who believe, no proof is required; for those who cannot believe, no proof is possible. [variation, Stuart Chase]
o Unfortunately, in science what You 'believe' is irrelevant. ["Orion", HBA forum]
o Only fools and charlatans know everything and understand everything." -Anton Chekhov

RE: Rocket general questions

SpaceX submits Starship mishap report to the FAA
By Mike Wall published 5 days ago
The agency is reviewing the report now.
https://www.space.com/spacex-submits-starship-mish...

SpaceX and FAA have some 'splainin to do'... hope the report is concise and clear and no 'BS'...

Regards, Wil Taylor
o Trust - But Verify!
o For those who believe, no proof is required; for those who cannot believe, no proof is possible. [variation, Stuart Chase]
o Unfortunately, in science what You 'believe' is irrelevant. ["Orion", HBA forum]
o Only fools and charlatans know everything and understand everything." -Anton Chekhov

RE: Rocket general questions

(OP)
why do you think the FAA has "some 'splainin' to do" ?

"Hoffen wir mal, dass alles gut geht !"
General Paulus, Nov 1942, outside Stalingrad after the launch of Operation Uranus.

RE: Rocket general questions

Rb...

So far the FAA has been 'mum' on this launch mishap... and appears to be allowing SpaceX to write the entire report... with nothing but FAA 'review'. And the FAA appears to be mum on the SpaceX operations and the local community. This process simply does NOT seem kosher.

Regards, Wil Taylor
o Trust - But Verify!
o For those who believe, no proof is required; for those who cannot believe, no proof is possible. [variation, Stuart Chase]
o Unfortunately, in science what You 'believe' is irrelevant. ["Orion", HBA forum]
o Only fools and charlatans know everything and understand everything." -Anton Chekhov

RE: Rocket general questions

(OP)
I'd've thought that NASA had more relevant experience and opinion.

I wonder if they'll change "Aviation" to "Aerospace" ? since the FAA is getting more involved in space.

"Hoffen wir mal, dass alles gut geht !"
General Paulus, Nov 1942, outside Stalingrad after the launch of Operation Uranus.

RE: Rocket general questions

Ya gotta aviate before you get orbital...

But, yeah, why not involve the experts (NASA) in any failure/accident investigation...

And yes, that can be taken ironically or not...NASA certainly has experience in space accident investigations.

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