SpaceX F9 : Crew Dragon In-Flight Abort Test : Jan. 19, 2020 : Discussion

[Alexphysics]

I'm starting to wonder if this is a thread about the in flight abort or a NASA conspiracy thread. It ends up being tiring seeing people complaining about the parachute tests when literally all we know is what is public and no one knows what happens "behind the curtains". If anyone really thinks doing this is easy or that SpaceX is really good to go I suggest y'all to fund your own aerospace company to launch humans into orbit and dock with the ISS and bring them back safely with the highest safety standards ever.

[joek]

Shouldn't self destruct destroy both stages?  At the time of the explosion both stages are in the same place, heading in the same direction, threatening roughly the same point of impact.  If one blows it's difficult to see why the other wouldn't.

I'm sure there are edge cases where the height of the rocket means one stage is inside the corridor and the other outside, but that would require extreme precision from a non-nominal rocket.

Not necessarily.  If the stack is still coupled, probably.  But remember that S2 separates from S1 and SC (Dragon) separates from S2.  So if you look at it from a "command authority" and timing perspective, SC is at the top, followed by S2, followed by S1.

What happens if they disagree when all are coupled is anyone's guess (mine is that SC has ultimate authority).  When S1 separates from S2 does it still have some level of autonomy (at least as to destruct)?  Maybe (probably, at least in nominal cases as IIRC we have heard the S1 AFTS-safe call-out S1 post-separation).  When S2 separates from SC does it still a have similar level of autonomy?  Again, maybe (and again, probably, although I don't recall ever hearing S2 AFTS-safe call-out).

[RotoSequence]

Wow. Look at that. I thought it would be shredded/smashed up! 

There was a piece inside of the trunk that covered the heatshield that's no longer present, so it's shed at least some bits.

[joek]

My understanding was that the command that initiated the abort was a command to the F9 Merlin's to *reduce* thrust.  D2 detected the lost of thrust and commanded engine shut down as part of its abort process.
...

Any such understanding is a questionable interpretation of statements which IMO clearly state otherwise.  All that was stated during the presser Q&A was that SpaceX "tightened parameters".  What parameters were not specified.  What was clarified during the presser Q&A was that F9 engine shutdown was *not* the initiating-causal event.

[su27k]

As to S1 sudden breakup... I am wondering if S1 sensed it had left it's auto self destruct corridor and triggered it's self destruct system... 

Shouldn't self destruct destroy both stages?  At the time of the explosion both stages are in the same place, heading in the same direction, threatening roughly the same point of impact.  If one blows it's difficult to see why the other wouldn't.

Second stage FTS may not even be armed, since it has no engine, it can't fly out of the exclusion zone and endanger the public.

[gongora]

The plan was not to trigger AFTS unless the vehicle went on a bad trajectory.  The environmental assessment said this.  It was said in no uncertain terms at the pre-launch press conference.

But remember, NASA said that the analysis of the Dragon 2 parachute failure showed that the accepted modeling was inadequate despite decades of use and acceptance. Orion and Starliner used those models to do verification of their parachutes. Yet both were allowed to continue without new drop tests.
Did either of those programs have to update their models and recertifications?

Did either of those programs have parachute failures that required a redesign to strengthen the chutes?  Dragon did.

[joek]

But remember, NASA said that the analysis of the Dragon 2 parachute failure showed that the accepted modeling was inadequate despite decades of use and acceptance. Orion and Starliner used those models to do verification of their parachutes. Yet both were allowed to continue without new drop tests.
Did either of those programs have to update their models and recertifications?

How much do we know about this "Mark III" parachute design?  Very little.[1]  How much do we know about the differences between this design and previous, potentially more conventional and well-modeled systems?  Very little.  How much do we know whether the models of this new design accurately reflect what has been observed in testing?  Very little.

Yeah, there may be an overabundance of caution.  But would not be surprised if this new-improved Mark III system held some surprises which caused pause in some quarters.  It's a set of parachutes, right?  We've done this for years, right?  What possible new-and-potentially-radical improvements could SpaceX's Mark II have which might upset the cart and make our old models questionable?

I have no idea what's really in play.  But I think it's safe to say that SpaceX might not have been satisfied with the humdrum well-proven designs (and models) and as typical, gone their own route...and thus the need-desire on NASA's part to perform additional validation.


[1] Speaking for myself.  Have seen little-to-no details.  Anyone?

[Lars-J]

That trunk is pretty sturdy... (see updates thread) - Ready to be reused? 

[joek]

The plan was not to trigger AFTS unless the vehicle went on a bad trajectory.  The environmental assessment said this.  It was said in no uncertain terms at the pre-launch press conference.
...

Yes, but by definition AFTS is autonomous.  Question is: Was it armed?

[su27k]

This is exactly what I’m talking about...haven’t SpaceX successfully completed 10 consecutive Mark 3 parachute tests (11 if you include today’s)...what more does NASA want with SpaceX...??..

Only two system-level tests have been completed, today's being the second.  From comments during the presser today, the other tests have been, e.g., single-chute unit tests or similar, and that they have two (or maybe one?) more system-level tests in-plan based on the relatively recent move to the "Mark III" design.

Are those additional tests unwarranted and a tactic to delay SpaceX?  Don't think so.

We don't know what system-level tests mean in this context, too bad nobody asked about it. We do know SpaceX completed 10 successful multi-chute test in a row of mark 3 design based on this tweet:

https://twitter.com/spacex/status/1209201762596356096

So, no, the other tests are not just single-chute unit tests.

[joek]

So, no, the other tests are not just single-chute unit tests.

As stated "single-chute unit tests or similar".  What is the difference between those and "system" tests?  No idea.  However, during presser Q&A the answer was quite clear: only two "system" level tests have been performed.  So obviously those multi-chute tests were not considered "system" level tests.

[su27k]

So, no, the other tests are not just single-chute unit tests.

As stated "single-chute unit tests or similar".  What is the difference between those and "system" tests?  No idea.  However, during presser Q&A the answer was quite clear: only two "system" level tests have been performed.  So obviously those multi-chute tests were not considered "system" level tests.

I don't think single chute and multi-chute tests are similar, in fact Elon Musk specifically made a clarification  to distinguish them:

https://twitter.com/elonmusk/status/1191475073758064640

You say "only" two system level tests have been performed, but we don't know what is the necessary number of system level tests either. Boeing only did 2 development tests, 5 qualification tests and 3 reliability tests in total. So 2 is not necessarily a small number in this context.

[lonestriker]

My understanding was that the command that initiated the abort was a command to the F9 Merlin's to *reduce* thrust.  D2 detected the lost of thrust and commanded engine shut down as part of its abort process.
...

Any such understanding is a questionable interpretation of statements which IMO clearly state otherwise.  All that was stated during the presser Q&A was that SpaceX "tightened parameters".  What parameters were not specified.  What was clarified during the presser Q&A was that F9 engine shutdown was *not* the initiating-causal event.

There's definitely a bit of conflicting descriptions about the abort sequence.  So it would be great if someone could get the official SpaceX timeline (as Elon hinted at, describing the events down to the ms level.)

From the SpaceX press kit:

For this test, Falcon 9’s ascent trajectory will mimic a Crew Dragon mission to
the International Space Station to best match the physical environments the
rocket and spacecraft will encounter during a normal ascent. However, SpaceX
has configured Crew Dragon to intentionally trigger a launch escape after Max
Q, the moment of peak mechanical stress on the rocket.

That sounds like D2 just triggers the abort without a precipitating event (i.e problem with F9 itelf.)

John describes sequence of events in the web stream:

We'll fly until Falcon 9 reaches a pre-determined velocity... approx 20 km up.  Once we reach the required velocity, Dragon will then trigger an escape.  Now as a reminder, the ground is not commanding this abort. It's up to the onboard computers to determine when to trigger the launch escape, and do all the functions afterward.  Once Dragon does trigger the launch escape, the first event will be commanding Falcon 9 to shutdown its nine Merlin engines.

John says "shutdown and Dragon escape"


So, I'm now on the side of D2 causing the F9 engine shutdown at this point and not the F9 engine shutdown as the precipitating event.  I'll have to dig up earlier SpaceX messages to see if there was a conflicting statement previously, but haven't found anything yet.

[joek]

You say "only" two system level tests have been performed, but we don't know what is the necessary number of system level tests either. Boeing only did 2 development tests, 5 qualification tests and 3 reliability tests in total. So 2 is not necessarily a small number in this context.

IIRC from the presser they have two more system level tests more in-plan; assume that (total of 4 system tests) is the requisite number, assuming results are nominal.

[Vettedrmr]

So, I'm now on the side of D2 causing the F9 engine shutdown at this point and not the F9 engine shutdown as the precipitating event.  I'll have to dig up earlier SpaceX messages to see if there was a conflicting statement previously, but haven't found anything yet.

Question:  Why do we care?  The point of the flight was to demonstrate D2's ability to safely escape a failing Falcon, not to determine various types of failure criteria.  So what if DM-2 shut down the engines?  What does that prove for this flight?

[Nomadd]

So, I'm now on the side of D2 causing the F9 engine shutdown at this point and not the F9 engine shutdown as the precipitating event.  I'll have to dig up earlier SpaceX messages to see if there was a conflicting statement previously, but haven't found anything yet.

Dragon commanding the engine shutdown doesn't mean the abort wasn't triggered by loss of thrust. Engine shutdown and abort thrusters firing are two different things.

[joek]

Question:  Why do we care?  The point of the flight was to demonstrate D2's ability to safely escape a failing Falcon, not to determine various types of failure criteria.  So what if DM-2 shut down the engines?  What does that prove for this flight?

Question for many is: What does this prove?  It proves that in a nominal abort situation, that Dragon performed nominally (if "nominal" and "abort" in the same phrase makes sense).  That said, the difference between Dragon initiating the shut-down of F9, or responding to a loss of thrust by F9--or some other event unrelated to F9 loss of thrust--is important.  (Many things other than loss of F9 thrust might lead to an abort.)

And yes, this did show--at least to some extent--response to "various types of failure criteria".  It showed Dragon detected and responded properly to at least one of them; that is obviously a necessary prerequisite to a safe escape in such situations.  At the risk of stating the obvious: if Dragon cannot detect and respond appropriately, then nothing else matters.

[su27k]

You say "only" two system level tests have been performed, but we don't know what is the necessary number of system level tests either. Boeing only did 2 development tests, 5 qualification tests and 3 reliability tests in total. So 2 is not necessarily a small number in this context.

IIRC from the presser they have two more system level tests more in-plan; assume that (total of 4 system tests) is the requisite number, assuming results are nominal.

Yes, the presser did say they have 2 more system level tests planned, but during the presser Bridenstine also said he and Elon agreed that SpaceX will "get as much [mark 3] testing as we can possibly get done between now and the day we launch crew", so I'm not sure it's correct to say 4 is the requisite number, it's possible the 2 extra tests are nice to haves, not must haves, and that SpaceX is going above and beyond what is required to ensure crew safety.

[joek]

Dragon commanding the engine shutdown doesn't mean the abort wasn't triggered by loss of thrust. Engine shutdown and abort thrusters firing are two different things.

Correct; the abort was *not* triggered by loss of F9 thrust, but by Dragon based on other criteria, as addressed during the presser Q&A (see numerous posts above).

[joek]

Yes, the presser did say they have 2 more system level tests planned, but during the presser Bridenstine also said he and Elon agreed that SpaceX will "get as much [mark 3] testing as we can possibly get done between now and the day we launch crew", so I'm not sure it's correct to say 4 is the requisite number, it's possible the 2 extra tests are nice to haves, not must haves, and that SpaceX is going above and beyond what is required to ensure crew safety.

Good point... so maybe not two more are required but desirable.  Which raises the question of what is "required" vs. "desirable".  I expect at minimum one additional system test unless they got everything they think they need from this test.