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

[joek]

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.

[gongora]

[According to Kathy there are still some parachute tests to do.  I think she mentioned they are waiting on another set.

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...??..

Again, i ask the question, after today’s test, which of the first Commercial Crews would fly on their respective spacecraft tomorrow...my bet would be with Dragon 2...

They've only done 2 tests of the full parachute system.

[John Alan]

My opinion... the safest way to get people to orbit ever... just passed it's final exam (worst case abort)

Sure... cross the T's and dot them I's NASA... but leave politics out of this... PLEASE!!

The Chicago (sorry, need to stop here for a second and just say that I have to use stupid words to get my point across. I know that means I must have a weak argument, but that's why I use bad words). (Boeing) and the Alabama (sorry, need to stop here for a second and just say that I have to use stupid words to get my point across. I know that means I must have a weak argument, but that's why I use bad words). (ULA,Sen. Shelby) need to now realize they should be #2 now to fly humans to ISS... but they will have their day to shine soon enough...

If Doug and Bob (or heaven forbid Mike and/or Vic) do NOT fly on Demo-2 before July 4th 2020... there SHOULD be a public outcry and congressional investigation why it's taking so long...

IMHO... 

https://en.wikipedia.org/wiki/Crew_Dragon_Demo-2

On edit...
I like the fact the website will not let me use the M word (auto corrects to as it reads above).. fair enough... that's Kewl... 

[CJ]

I've watched the stabilized and enhanced vid posted upthread (thank you!) and IMHO, the pieces exiting the fireball heading forward are not the Merlins; the relative velocity is too high.

That fireball was pretty violent to be able to accelerate components like we saw (this looked a lot more violent than CRS-7 IMHO). My guess is that the partially-empty tanks failed structurally, resulting in compromising at least one S1 COPV, creating a pressure pulse. Or... was this a deliberate triggering (via internal overpressure) of the kind we saw when Grasshopper II (I forget the real name) destructed over McGreggor?

In the video, it looks to me as if there was some structural deformation (bending) right before the kaboom, but I am not sure.

I hope they got good data from the F9 up until the kaboom, because it might hold valuable data on breakup, structural issues, etc.   

[joek]

My opinion... the safest way to get people to orbit ever... just passed it's final exam (worst case abort)
...

That was not a worst case abort.  A worst case abort would be if the commanded F9 engine shutdown did not happen and F9 continued boosting.  Or if separation between Dragon and the LV during abort did not occur in a timely manner.  As mentioned during the presser, those should be survivable--but that is not what we saw today.  (And would likely involve multiple safety system related failures.)  So "worst case"?  No.  But enough to demonstrate nominal abort capability and crew suitability; pretty much best that can be done and demonstrably better than most.

[Tommyboy]

Wow, John Kraus got a photo of the part that hit the water.

The actual part before impact:
https://twitter.com/thejackbeyer/status/1218927117443969025/

Looks like S2+Interstage.

To me it looks like the first stage and interstage, like Jarnis said.

You are most definitely wrong. The black piece is too long to be the octaweb, so it must be the interstage. There was a BIG fireball on impact with the ocean, so there must have been RP1. Considering there is a lox tank between the S1 RP1 tank and the interstage, and that the falling debree was too short for an entire S1+interstage, there is no other option than S2+interstage.

[John Alan]

My opinion... the safest way to get people to orbit ever... just passed it's final exam (worst case abort)...

That was not a worst case abort.  A worst case abort would be if the commanded F9 engine shutdown did not happen and F9 continued boosting.  Or if separation between Dragon and the LV during abort did not occur in a timely manner.  As mentioned during the presser, those should be survivable--but that is not what we saw today.  (And would likely involve multiple safety system related failures.)  So "worst case"?  No.  But enough to demonstrate nominal abort capability and crew suitability; pretty much best that can be done and demonstrably better than most.

Fair enough... I should have said worst case as far as aerodynamic loads ...

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... 
And I agree with others that S2, (with the inter-stage attached, full of LOX and RP-1), made it to the ocean surface intact where it blew up on impact...  That's one tough structure it seems...

[Rondaz]

Crew Dragon separating from Falcon 9 during today’s test, which verified the spacecraft’s ability to carry astronauts to safety in the unlikely event of an emergency on ascent

https://twitter.com/SpaceX/status/1218976479150858241

[TheRadicalModerate]

I've watched the stabilized and enhanced vid posted upthread (thank you!) and IMHO, the pieces exiting the fireball heading forward are not the Merlins; the relative velocity is too high.

That fireball was pretty violent to be able to accelerate components like we saw (this looked a lot more violent than CRS-7 IMHO). My guess is that the partially-empty tanks failed structurally, resulting in compromising at least one S1 COPV, creating a pressure pulse. Or... was this a deliberate triggering (via internal overpressure) of the kind we saw when Grasshopper II (I forget the real name) destructed over McGreggor?

In the video, it looks to me as if there was some structural deformation (bending) right before the kaboom, but I am not sure.

I hope they got good data from the F9 up until the kaboom, because it might hold valuable data on breakup, structural issues, etc.

I don't understand how you could get RP-1 and LOX to mix efficiently enough to generate that kind of a deflagration.  Seems like you'd need both tanks to rupture at almost the same time and vent enough aerosol into an interior space to get that kind of energy.

[joek]

...
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... 
...

Bet multiple systems were in play but that Dragon-commanded abort was the causal factor... "boss says abort, I abort... that means... engine shutdown, then unzip, ..." vs. "no word from the boss but I think we are way off... tell boss... no response from boss... engine shutdown, unzip, ..." Or something like that.

[CorvusCorax]

I've watched the stabilized and enhanced vid posted upthread (thank you!) and IMHO, the pieces exiting the fireball heading forward are not the Merlins; the relative velocity is too high.

That fireball was pretty violent to be able to accelerate components like we saw (this looked a lot more violent than CRS-7 IMHO). My guess is that the partially-empty tanks failed structurally, resulting in compromising at least one S1 COPV, creating a pressure pulse. Or... was this a deliberate triggering (via internal overpressure) of the kind we saw when Grasshopper II (I forget the real name) destructed over McGreggor?

In the video, it looks to me as if there was some structural deformation (bending) right before the kaboom, but I am not sure.

I hope they got good data from the F9 up until the kaboom, because it might hold valuable data on breakup, structural issues, etc.

I don't understand how you could get RP-1 and LOX to mix efficiently enough to generate that kind of a deflagration.  Seems like you'd need both tanks to rupture at almost the same time and vent enough aerosol into an interior space to get that kind of energy.

In that context it has been suggested that - considering a shared bulkhead between RP1 and LOX tanks - rupture of one tank might cause the bulkhead to invert/rupture, with the effect that one tank losing pressure will automatically fail the other.
This will also create a vent, exactly where the tanks join, and cause the still-at-full-pressure tank to vent into the lower pressure venting tank. So the only way for the Lox to get out - at this point - is through the RP1

If you look at the 4k boom-footage frame by frame, you can see exactly that. a first, yellow flame, creating a fireball, that is then followed by a much more violent and larger fireball shortly after.

I can't tell which tank burst first, Lox or Rp1, but it definitely made a nice big BOOM!

This one:   single step - available from different angles - 25 seconds in

[Zpoxy]

Has anyone compared the Orion AA2 to the Dragon-2 IFA?

Boeing Orion Ascent Abort
https://www.youtube.com/watch?v=zrq71ocWMcg?t=124

Comments on the apparent booster to capsule separation speeds between the 2?

Lockheed Martin, not Boeing.

[JeffreyLind]

So this is unrelated to the current discussion happening in chat but will recovery vehicles like GO Searcher still be deployed during every crew dragon launch in case of an abort or will they just be on standby in port

[eriblo]

...
Comments on the apparent booster to capsule separation speeds between the 2?

Hard to compare based on that video.  Also questionable apples-oranges comparison.  Too many differences in the environments, LV's and LAS systems.  For example, Orion LAS is essentially full-out once they light it up.  Have not seen information on what kind of G's that imparts.  Dragon LAS can be modulated--and apparently was during this test with 3.5G limit.

Per comments during the presser, Dragon LAS can push 6+ G's; how Dragon might determine if-when that is necessary or how it might change the SC-LV distance is unknown.  Maybe it is capable of determining effectiveness of booster shutdown command before deciding?  Maybe it has a way of knowing nominal distance from LV in the initial phase before deciding?  And if it is not sure, maybe it puts pedal-to-the-metal (which we did not see today)?

Not to mention other differences, such as Orion LAS is jettisoned relatively early in flight; whereas Dragon LAS is available all the way to orbit.  How does that change the equation?

An interesting comparison and probably worthy of its own thread (not this one).

It does not make much sense to abort at less than maximum thrust since even the maximum acceleration is fairly benign (compared to other aborts). Remember that the 3.5 Gs is what is left after overcoming air resistance at max Q.

[eriblo]

I have seen some comments regarding whether the AFTS activated (or should have) so I will just post my speculation. The primary task of the AFTS is to ensure that the instantaneous impact point of the Falcon 9 never leaves the approved corridor. Which by definition will not happen if the thrust is cut...*

The only caveat is that they could have a secondary function of the AFTS to minimize collateral damage and environmental impact at ground level by dispersing the stage and its contents, but I do not think that they would have said that it had a (very small) chance of impacting intact in that case.

*One could consider that the Falcon 9 S1 could in theory maneuver aerodynamically at which point AFTS activation would be motivated.

[TorenAltair]

about the 700ms response time: it is a huge difference between actions and REactions per minute. A human reaction needs about 100-200 ms.

about the press conference: intended or slip of the tongue by Bridenstine? "this spacecraft knows precisely where it is in space [...] it constantly knows where it is supposed to be"

[Barley]

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.

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.

[joek]

It does not make much sense to abort at less than maximum thrust since even the maximum acceleration is fairly benign (compared to other aborts). Remember that the 3.5 Gs is what is left after overcoming air resistance at max Q.

Assuming that "It does not make much sense to abort at less than maximum thrust..." refers to purposes of testing, and specifically this test... the SpaceX test was at "max drag" (their words)--a bit later than max Q as the noted during the test call-outs.

So did it abort at max F9 thrust?  Maybe for a short period, until the F9 engine shutdown took effect.  But separation between Dragon-F9 is more than what happens in that instant.  Suppose that the F9 engine shutdown failed and that F9 kept boosting?

To achieve sufficient Dragon-F9 distance in a timely manner means more than simply overcoming residual aerodynamic resistance.  It also means (in a worst case) that Dragon can sufficiently outrun F9 should F9 keep boosting.

We did not see that situation today, although it was touched upon during the presser--and the answer was that Dragon could still outrun F9 in that situation to achieve sufficient separation.  That would likely require more than 3.5G boost by Dragon, as it would also require overcoming F9's continuing boost (again, worst case).

The details as to how Dragon might make the decision to increase boost in that situation was not discussed during the presser.

[Comga]

[According to Kathy there are still some parachute tests to do.  I think she mentioned they are waiting on another set.

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...??..

Again, i ask the question, after today’s test, which of the first Commercial Crews would fly on their respective spacecraft tomorrow...my bet would be with Dragon 2...

They've only done 2 tests of the full parachute system.

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?

[cbarnes199]

Apologies if this has been asked...

In this test ALL of the Merlins shutdown, and then the abort initiated...

I imagine there is a constantly evolving algorithm that would evaluate all the variables, and then relative to one, two, four engines out when to proceed to abort.

Thinking of the Falcon9 & CRS flight that lost one engine on the climb would not merit pulling the lever and aborting...

Thoughts and or informed opinions, maybe even facts about abort criteria parameters?

In the press conference, Elon seemed to say that they deliberately tightened the parameters for an automatic abort so that they would trigger at a certain part of the flight.  Once the Dragon decided an abort was necessary, it commanded the Merlins to shut down.  Without waiting for confirmation that that had happened, it then released itself from the Falcon second stage, armed and fired the super-Dracos.  All in the space of less than a second.

So the trigger for the abort was not any malfunction of the Falcon, but rather the Falcon behaving normally and the Dragon being overly picky about that behavior.  On purpose.  For the sake of the test.

Now they simply have to return the definition of "normal" back to the real normal.

I don't think this is correct.  From the SpaceX webcast, John said that they would command the F9 S1 engines to shutdown to start the sequence of events.  D2 would have detected the off-nominal condition and initiated the abort.  Elon mentioned that they did tighten up the parameters, but I think that just meant that instead of aborting at x% thrust out of band, they aborted at (x - delta)% thrust loss.  So a just make it abort more easily.

But, the abort is all in the hands of D2 itself. It wouldn't be much of an abort test if they also commanded D2 to abort.  That decision has to be made by the computers themselves, not humans.  The confusion comes from the fact that as D2 aborts, it ALSO commands the F9 S1 to cut thrust (but that was already done since that was what triggered everything to start with.)

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.

What I think Elon said was that they reduced the sensitivity of D2 to how much thrust could be lost before an abort was trigger thereby making D2 very sensitive to any loss of thrust.  It is possible that the loss of thrust that triggered the abort today was less than what might happen during an engine out event.  Hopefully in a normal flight D2 would not be triggered by an engine out if the orbit could still be achieved.

This might be why D2 was able to pressurize and ignite its Super Dracos before the F9 Merlin's had even come close to shutting down.