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

[lonestriker]

From Spaceflight Now article:

"U.S. military search and rescue teams deployed in the Atlantic Ocean practiced procedures to approach the capsule after splashdown. The teams from Patrick Air Force Base just south of Cape Canaveral would rescue astronauts from the spacecraft after a launch abort."

From NASA Press Release
"Teams of personnel from SpaceX and the U.S. Air Force 45th Operations Group's Detachment-3 out of Patrick Air Force Base will recover the spacecraft for return to SpaceX facilities in Florida and begin the recovery effort of the Falcon 9, which broke apart as planned."

I thought with the commercial space flight the US military (Navy and Air Force) were not to be involved in the recovery - is this only in the case of an abort? Would they be stationed on stand-by in the Atlantic Ocean for each launch? Any other units involved?

Thanks.

article: https://spaceflightnow.com/2020/01/19/spacex-aces-final-major-test-before-first-crew-mission/

As I understand it the "Guardian Angels" are on call if rescue is needed, just as Air Force demolitions specialists are on call to destroy any potentially dangerous rocket fragments.

Air Force has always provided range security, after all.

They wouldn't be used in a normal, planned recovery.  SpaceX and Boeing would have their assets deployed in those situations for nominal recoveries.  AAUI, the Guardian Angels are available world-wide for emergency recoveries.  It makes sense to use this IFA as a training opportunity for them as it's not likely they'll get this chance otherwise given the very low flight rates we're talking about.

[Lars-J]

Is it possible to reuse the trunk, or is it one-use only?

Look at the "nose" of it. it's very crunched up. It's completely missing the bracing arms that stiffen the trunk (see picture from pad abort below), which is also where the bolts for attaching the capsule are.

Some components may be salvageable.

Thanks for posting that... I noticed that the trunk design had evolved since the launch abort test (not surprising), and in this comparison we can see that either the flat structure under the heatshield was simplified, or another smooth layer was added on top for additional protection. (most likely the latter)

Hopefully SpaceX will post higher quality video/stills now that they have Dragon back in their processing center.

EDIT: hard to tell from the bad quality stream, but it looks like the 6 connection points between trunk and capsule might have been reduced to just 4. (hard to see in this image, easier if going frame by frame on video)

[yg1968]

Did Elon said that they would like to catch the Dragon with a net?

Yes he did.

Yes, he discussed this at 18m of this video:

[Rondaz]

She’s back! The #CrewDragon spacecraft that completed the in-flight abort test has arrived back at Cape Canaveral. After splashdown, teams from @SpaceX & the @usairforce 45th Operations Group’s Detachment-3 rehearsed crew recovery ops before bringing the spacecraft back to port.


https://twitter.com/JimBridenstine/status/1219372664298659840

[TheRadicalModerate]

As Elon said in the post-presser, it's more of a fireball than an explosion. Highly unlikely there would be a shockwave that could crush the CrewDragon.  Plus the base heat shield, which is designed to handle heat, as also stated by Elon in the presser.

And the reaction times to these types of abort scenario events are usually in the range of milliseconds, not a couple of seconds.

There are deflagrations that generate shockwaves, and ones that don't.  As an example, the initial Amos 6 explosion probably didn't, but when the core stage blew up a few seconds later, that almost certainly did--you could hear the difference on the video.

Don't confuse the reaction time to initiate the separation with the time require to reach minimum safe distance.  The former is indeed only a few tens of milliseconds, maybe 100 ms.  That later is highly scenario-dependent, but is likely a few seconds--as it was in this case.  However, in all scenarios, engine shutdown telemetry or complete loss of telemetry are both pretty good indicators that it's time to go.  So the test was likely close to worst survivable case, which is what you'd want.

observe fire movement during first stage explosions. Notice plural, because there were numerous COPV explosions. More of it if you will look at the video you would see that Dragon would have chance to survive even in ATMOS-6 variant (static explosion of the second stage).
More of CRS-7 dragon 1 survived  a real "explosion" of the second stage + total destruction even without using super dracos (just thanks to air-dynamic and inertia).
Gas/fuel explosions are slow and take time to build up and happen. There should be leak, the gases should mix in the right proportion etc. It all takes time which can be detected at time and reacted upon.'

Yes Dragon 2 is not going to survive C-300 warhead or anything of a kind. It's not designed for.

Some gas/fuel explosions are slow; others are not so slow.  For example, a semi-contained explosion from a failed LOX/RP-1 bulkhead could generate a pretty big bang.  Compare the initial AMOS-6 S2 explosion to the subsequent S1 explosion.  All deflagrations have some capability to produce an overpressure at a certain distance from the explosion, and that overpressure may be enough to crush or burst the spacecraft.

On Apollo, NASA estimated that the forward and crew compartment heat shields could be crushed with a 6.1 psi overpressure.  That overpressure varied based on what stage exploded, the altitude of the explosion, and the amount of time the CM had to escape before the explosion.  S-1C explosions could be fatal on the pad for escape times less than 2.5 seconds, and almost as dangerous near max-q (where the dynamic pressure is added to the overpressure).  S-II explosions were roughly the same because, while there was less fuel, they were closer to the CM.  S-IVB explosions weren't too bad on the pad, but got progressively worse up to fairly high altitudes.

Now:  The only kerolox stage on the Saturn V was the S-1C, and it had 5x the prop as an F9 core.  I would assume that hydrolox explosions were worse, so it's also possible that the F9 S2 wouldn't generate a sufficient overpressure, even though the F9 S2 actually has a bit more kerolox prop in it than the S-IVB had hydrolox.  In general, I'd say that there were a lot fewer fatal explosion scenarios on the F9, but I'd be a bit surprised if there were no such scenarios.

[woods170]

Is it possible to reuse the trunk, or is it one-use only?

One use only. This trunk may LOOK intact but it is NOT intact. The entire forward end (where the capsule rested on top of it) has taken a major beating. The cross-brace is gone and the whipple shield with it. Dragon Claw (the umbilical between the capsule and the trunk) is completely ripped off. There is visible tearing and cracking of the composite main structure of the trunk at the forward end.

[woods170]

Is it possible to reuse the trunk, or is it one-use only?

Look at the "nose" of it. it's very crunched up. It's completely missing the bracing arms that stiffen the trunk (see picture from pad abort below), which is also where the bolts for attaching the capsule are.

Some components may be salvageable.

Thanks for posting that... I noticed that the trunk design had evolved since the launch abort test (not surprising), and in this comparison we can see that either the flat structure under the heatshield was simplified, or another smooth layer was added on top for additional protection. (most likely the latter)

Hopefully SpaceX will post higher quality video/stills now that they have Dragon back in their processing center.

EDIT: hard to tell from the bad quality stream, but it looks like the 6 connection points between trunk and capsule might have been reduced to just 4. (hard to see in this image, easier if going frame by frame on video)

Correct. The number of attachment points between capsule and trunk has been reduced to four.

The pad abort test used a prototype trunk and capsule sporting six attachment points, similar to what is still used on cargo Dragon.
The pad abort prototype trunk also featured a structural support and cover plate (inside the trunk) only.

The trunk used in the IFA much more resembles a flight trunk. It features the full whipple shield inside the trunk to protect Dragon's heatshield area from MMOD and other high velocity impact events.

[Semmel]

The trunk is on board GO Navigator.

https://twitter.com/Kyle_M_Photo/status/1219062943125508097

Can someone explain why this thing floats?

The obvious answer: Because its less dense than water.

I expect it to contain some non-structural foam to dampen noise levels for the payload inside. Like a fairing. This foam might act like floating helpers when in water. I have no idea if that is the case though.

[CorvusCorax]

I think, the best indication that Dragon would have survived the Stage1 breakup and midair conflagration is that Stage 2 did.

I would argue that, Dragon is very likely bith more protected and shielded and sturdy with its man-rated pressure vessel, reentry heat shields and projectile shield in the trunk than Stage 2 with its thin AlLi propellant tanks. Yet it made it out intact.

Falcon 9 is one durable piece of rocketry

[erv]

Just curious - any speculation on where had that whipple shield go? It is seen on separation and missing in Elon's pic. Torn off by aerodynamic forces during its freefall? On impact in ocean? Or maybe removed by recovery teams?

[whitelancer64]

Just curious - any speculation on where had that whipple shield go? It is seen on separation and missing in Elon's pic. Torn off by aerodynamic forces during its freefall? On impact in ocean? Or maybe removed by recovery teams?

Most likely popped out upon impact with the ocean.

[clongton]

Is it possible to reuse the trunk, or is it one-use only?

One use only. This trunk may LOOK intact but it is NOT intact. The entire forward end (where the capsule rested on top of it) has taken a major beating. The cross-brace is gone and the whipple shield with it. Dragon Claw (the umbilical between the capsule and the trunk) is completely ripped off. There is visible tearing and cracking of the composite main structure of the trunk at the forward end.

And this from a relatively low altitude and velocity in comparison to an orbital reentry.

[woods170]

Is it possible to reuse the trunk, or is it one-use only?

One use only. This trunk may LOOK intact but it is NOT intact. The entire forward end (where the capsule rested on top of it) has taken a major beating. The cross-brace is gone and the whipple shield with it. Dragon Claw (the umbilical between the capsule and the trunk) is completely ripped off. There is visible tearing and cracking of the composite main structure of the trunk at the forward end.

And this from a relatively low altitude and velocity in comparison to an orbital reentry.

It fell down from roughly 40 km up, impacting the ocean at terminal velocity. The fact that the basic structure is still mostly intact goes to show that SpaceX builds its stuff strong.

[clongton]

Is it possible to reuse the trunk, or is it one-use only?

One use only. This trunk may LOOK intact but it is NOT intact. The entire forward end (where the capsule rested on top of it) has taken a major beating. The cross-brace is gone and the whipple shield with it. Dragon Claw (the umbilical between the capsule and the trunk) is completely ripped off. There is visible tearing and cracking of the composite main structure of the trunk at the forward end.

And this from a relatively low altitude and velocity in comparison to an orbital reentry.

It fell down from roughly 20 km up, impacting the ocean at terminal velocity. The fact that the basic structure is still mostly intact goes to show that SpaceX builds its stuff strong.

I didn't realize the impact was at terminal velocity. Doesn't get any faster than that. Wow!
Yea, SpaceX does not build flimsy stuff!

[HVM]

No no. Second stage clearly did not fall with it's terminal velocity, but lot faster in mach numbers e.g. still de-accelerating, same can be true with the trunk. Terminal velocity -> drag = gravity. Did woods170 forget that rockets fly mainly in sideways and not up;P

clongton's sarcasm is too dense for me.

[TheRadicalModerate]

I think, the best indication that Dragon would have survived the Stage1 breakup and midair conflagration is that Stage 2 did.

I would argue that, Dragon is very likely bith more protected and shielded and sturdy with its man-rated pressure vessel, reentry heat shields and projectile shield in the trunk than Stage 2 with its thin AlLi propellant tanks. Yet it made it out intact.

Falcon 9 is one durable piece of rocketry

Even if it turns out that the falling piece really is the S2 (Musk seemed think it might be core thrust structure, although the paint scheme looks more like interstage and S2 to me), I'd point out that there's a huge amount of difference between "intact" and "apparently in one piece".  The D2 needs to be intact enough to be able to jettison the trunk, reenter, and pop the 'chutes.

[ugordan]

No no. Second stage clearly did not fall with it's terminal velocity, but lot faster in mach numbers e.g. still de-accelerating, same can be true with the trunk. Terminal velocity -> drag = gravity. Did woods170 forget that rockets fly mainly in sideways and not up;P

I'm pretty sure the ballistic coefficients of a (pretty much fully) loaded 2nd stage and an empty structural shell are sufficiently different so as to not warrant any mutual comparison. In this respect, I will agree with woods170 in that the Dragon trunk pretty much impacted at terminal velocity.

[envy887]

I think, the best indication that Dragon would have survived the Stage1 breakup and midair conflagration is that Stage 2 did.

I would argue that, Dragon is very likely bith more protected and shielded and sturdy with its man-rated pressure vessel, reentry heat shields and projectile shield in the trunk than Stage 2 with its thin AlLi propellant tanks. Yet it made it out intact.

Falcon 9 is one durable piece of rocketry

Even if it turns out that the falling piece really is the S2 (Musk seemed think it might be core thrust structure, although the paint scheme looks more like interstage and S2 to me), I'd point out that there's a huge amount of difference between "intact" and "apparently in one piece".  The D2 needs to be intact enough to be able to jettison the trunk, reenter, and pop the 'chutes.

"Intact enough" to do those things is a fairly low bar. As long as the pressure vessel hasn't been holed by a huge chunk of shrapnel, it would probably be fine.

[ugordan]

It fell down from roughly 20 km up, impacting the ocean at terminal velocity. The fact that the basic structure is still mostly intact goes to show that SpaceX builds its stuff strong.

I mean, you could make the case that the fins on the trunk made it stabilize in the "prograde" direction on the way down, which is its normal load-bearing configuration so it's not such a surprise that the ring survived, but the whipple shield getting knocked out.

What is intriguing to me is that the S2+interstage managed to stay in one piece just a few (tens of?) meters above sea level, when it let go as well. Evidence that it was still supersonic/highly subsonic near ocean impact that the reflected shockwave is what actually caused it to blow? My gut feeling says that such a shockwave should not be powerful enough compared to what the stage experienced slowing down earlier, but I don't have another plausible explanation other than, say, AFTS triggering in ground proximity. Yet, I'd think AFTS only concerns itself with the 2D launch corridor, not altitude inside that corridor. So many questions...

[HVM]

No no. Second stage clearly did not fall with it's terminal velocity, but lot faster in mach numbers e.g. still de-accelerating, same can be true with the trunk. Terminal velocity -> drag = gravity. Did woods170 forget that rockets fly mainly in sideways and not up;P

I'm pretty sure the ballistic coefficients of a (pretty much fully) loaded 2nd stage and an empty structural shell are sufficiently different so as to not warrant any mutual comparison. In this respect, I will agree with woods170 in that the Dragon trunk pretty much impacted at terminal velocity.

Quick calc for lower atmosphere:
Terminal velocity for 2nd stage: ~1386 km/h (So it can be at terminal v.)
Terminal velocity for trunk:  ~130 to 60 km/h so there's nothing special for trunk's condition, if true.

Abort v ~1648 km/h at last telemetry reading for us. +SuperDrago *kick for the trunk.

*) Yoink coz SD are higher than trunk.