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

[HVM]

Is it just me, or do these two official pictures of SpX-IFA look a bit fake?

I think it looks like someone made a detailed painting of the abort.

Someone is hit them with strong Noise Reduction...

> indaco1
With extra +800 km/h horizontal velocity; deacceleration of the drag chute opening would kill him, rip that drag chute apart, and later mains apart. And make him triple dead at impact. It's just same right.

> JamesH65
I don't write about second stage on those quotes.

[niwax]

Also noteworthy in those images: There was still flame coming out of the Merlins when the Dracos were already firing. With the capsule already taking off, this might be as late as t+1s after the abort was initiated.

[woods170]

What will become of this particular Dragon? Refurb?

I'm guessing it will end up as a museum piece.

Possibly will be hung from the ceiling at SpaceX Hawthorne.

I'm willing to bet that between the time they finish inspecting it and when it finds its final rest, it gets used for parachute system tests.

They don't need to because SpaceX has got another dedicated Crew Dragon built for exactly that purpose. It has already performed multiple all-up parachute drop tests.

[JamesH65]

> JamesH65
I don't write about second stage on those quotes.

Irrelevant to the point being made, which is whatever is falling from this height would have lost almost all horizontal velocity due to drag, and would be falling at approximately terminal velocity, due to drag. The velocity it had at height, either horizontal or vertical, is irrelevant* to the velocity it hit the water as it has passed through so much atmosphere.

* Note, irrelevant at the sort of velocities involved. Something going very very very fast (e.g. meteor, orbital vehicle) may well still maintain some of its original kinetic energy - not enough atmosphere to slow it down to terminal velocity

[joseph.a.navin]

What will become of this particular Dragon? Refurb?

I'm guessing it will end up as an museum piece.

I think the Smithsonian Udvar Hazy would be a good place, but then again I am biased. They could put it next to Discovery.

[woods170]

What will become of this particular Dragon? Refurb?

I'm guessing it will end up as an museum piece.

I think the Smithsonian Udvar Hazy would be a good place, but then again I am biased. They could put it next to Discovery.

Had the DM-1 vehicle not blown up and had it performed the IFA it still would have ended up at SpaceX headquarters in Hawthorne.

[clongton]

Also noteworthy in those images: There was still flame coming out of the Merlins when the Dracos were already firing. With the capsule already taking off, this might be as late as t+1s after the abort was initiated.

1. At the expected time of MaxQ, the F9 flight avionics, located in the upper stage, commands F9 engine shutdown by shutting down the propellant turbo pumps and closing the propellant feed valves.
2. The Dragon abort computer, located inside Dragon, detects the loss of thrust and commands abort execution.
That is the sequence of events afaik.

Even though the F9 engines are completely shut down with all propellant valves closed, there is still residual propellant in the feed lines, under residual and rapidly diminishing pressure. That residual propellant is burning on its way out the nozzles, even though the Merlins are not operating at all. That's the plume we see behind the F9 while the Dragon's SD begin firing. The entire sequence took only 700 milliseconds. The frames that showed the burning residual propellant and the Dragon's SD firing at the same time occupied only 2-3 milliseconds. It's amazing that an event that occupied such an incredibly short span of time was actually captured on camera. The chances of that happening are pretty small. It's an awesome photo, one for the record books.

[indaco1]

...
> indaco1
With extra +800 km/h horizontal velocity; deacceleration of the drag chute opening would kill him, rip that drag chute apart, and later mains apart. And make him triple dead at impact. It's just same right.
..

Baumgartner achieved a top speed of 1357 km/h during the jump, when he still was in the upper layers of the atmosphere.

Even simply composing the vectors, if you add an horizontal component of 800 km/h you get an absolute speed of 1575 km/h.  This is an upper limit, because par of horizontal speed is lost during the fall.

If a human body can withstand falling at 1357km/h at high quote, perhaps the trunk, designed to be exposed during a space launch, can fall at 1575 km/h and stay unaffected.

Drag/weight ratio of them is not so similar, of course. But when out of most of the atmosphere their fall from 40km should not be that different except for the horizontal component.

https://en.wikipedia.org/wiki/Red_Bull_Stratos

[envy887]

Also noteworthy in those images: There was still flame coming out of the Merlins when the Dracos were already firing. With the capsule already taking off, this might be as late as t+1s after the abort was initiated.

1. At the expected time of MaxQ, the F9 flight avionics, located in the upper stage, commands F9 engine shutdown by shutting down the propellant turbo pumps and closing the propellant feed valves.
2. The Dragon abort computer, located inside Dragon, detects the loss of thrust and commands abort execution.
That is the sequence of events afaik.

Even though the F9 engines are completely shut down with all propellant valves closed, there is still residual propellant in the feed lines, under residual and rapidly diminishing pressure. That residual propellant is burning on its way out the nozzles, even though the Merlins are not operating at all. That's the plume we see behind the F9 while the Dragon's SD begin firing. The entire sequence took only 700 milliseconds. The frames that showed the burning residual propellant and the Dragon's SD firing at the same time occupied only 2-3 milliseconds. It's amazing that an event that occupied such an incredibly short span of time was actually captured on camera. The chances of that happening are pretty small. It's an awesome photo, one for the record books.

The video SpaceX released has at least 20 distinct frames which all show both smoke/flames from the SDs and a significant flame still coming from the Merlins.

You can go frame by frame through the high-res sequence at 5:27 in the video by Scott Manley here:



Use the "," and "." keys to advance to go back one frame at a time.

That might be a high framerate video, buy I don't think so. The 20 frames or so appears to be realtime in 2/3rds of a second, at least to my eye. That would mean that full Merlin shutdown took at least 600 milliseconds after the SuperDracos started firing. Edit: as ugordan notes it's probably 60 fps video. Still ~100x longer than "2-3 ms" for shutdown, though.

And while the beginning of the sequence isn't very clear, it appears that the SDs start emitting smoke before there is any visible change in the Merlin plume, indicating that Falcon is still at full thrust when the abort decision has already been made and is being actively executed by the SDs.

[mn]

Also noteworthy in those images: There was still flame coming out of the Merlins when the Dracos were already firing. With the capsule already taking off, this might be as late as t+1s after the abort was initiated.

1. At the expected time of MaxQ, the F9 flight avionics, located in the upper stage, commands F9 engine shutdown by shutting down the propellant turbo pumps and closing the propellant feed valves.
2. The Dragon abort computer, located inside Dragon, detects the loss of thrust and commands abort execution.
That is the sequence of events afaik.

Even though the F9 engines are completely shut down with all propellant valves closed, there is still residual propellant in the feed lines, under residual and rapidly diminishing pressure. That residual propellant is burning on its way out the nozzles, even though the Merlins are not operating at all. That's the plume we see behind the F9 while the Dragon's SD begin firing. The entire sequence took only 700 milliseconds. The frames that showed the burning residual propellant and the Dragon's SD firing at the same time occupied only 2-3 milliseconds. It's amazing that an event that occupied such an incredibly short span of time was actually captured on camera. The chances of that happening are pretty small. It's an awesome photo, one for the record books.

The video SpaceX released has at least 20 distinct frames which all show both smoke/flames from the SDs and a significant flame still coming from the Merlins.

You can go frame by frame through the high-res sequence in the video by Scott Manley here:

https://www.youtube.com/watch?v=R-HOQrinzlY?t=327

Use the "," and "." keys to advance to go back one frame at a time.

That might be a high framerate video, buy I don't think so. The 20 frames or so appears to be realtime in 2/3rds of a second, at least to my eye. That would mean that full Merlin shutdown took at least 600 milliseconds after the SuperDracos started firing.

And while the beginning of the sequence isn't very clear, it appears that the SDs start emitting smoke before there is any visible change in the Merlin plume, indicating that Falcon is still at full thrust when the abort decision has already been made and is being actively executed by the SDs.

How long would we expect it take to shutdown the merlins from when command is issued? (do we have any other examples or info)

Edit: based on more recent info, it does seem that the abort was initiated by reaching a set speed (and not by detecting loss of thrust as had been speculated), which would mean the commands to start the SD's and to shut the merlins were issued at nearly the same time.

[billh]

Yes, I thought Elon made this very clear at the post flight press conference. They simply adjusted the limit on one of the abort parameters so that it would trigger at around 84 seconds into the mission. After that, everything that happened is part of the normal abort sequence: Dragon sends a shutdown message to Falcon, separates, and fires its SuperDracos. It doesn't wait for F9 thrust to decay after sending the shutdown message. It leaves immediately.

It makes sense that you would want to minimize alterations to the programming when you test it. Changing a fixed constant like an abort limit is the least intrusive thing you could do. After that, everything happens according to the standard abort logic.

[ugordan]

That might be a high framerate video, buy I don't think so.

I think it's virtually certain that it's higher rate than normal, some of the Cape trackers are certainly capable of high rate video, at least 60 fps. The vehicle is moving too slowly against the cloud backdrop compared to the live webcast video, Dragon is accelerating away too slowly (it takes it roughly 3sec to pull away 1 more F9 length in the tweet video), the time it takes for the base of 2nd stage to begin venting is 2x longer in the Twitter video than in the webcast.

My money is it's 60 fps footage played back at 30 fps.

[TheRadicalModerate]

1. At the expected time of MaxQ, the F9 flight avionics, located in the upper stage, commands F9 engine shutdown by shutting down the propellant turbo pumps and closing the propellant feed valves.
2. The Dragon abort computer, located inside Dragon, detects the loss of thrust and commands abort execution.
That is the sequence of events afaik.

Even though the F9 engines are completely shut down with all propellant valves closed, there is still residual propellant in the feed lines, under residual and rapidly diminishing pressure. That residual propellant is burning on its way out the nozzles, even though the Merlins are not operating at all. That's the plume we see behind the F9 while the Dragon's SD begin firing. The entire sequence took only 700 milliseconds. The frames that showed the burning residual propellant and the Dragon's SD firing at the same time occupied only 2-3 milliseconds. It's amazing that an event that occupied such an incredibly short span of time was actually captured on camera. The chances of that happening are pretty small. It's an awesome photo, one for the record books.

While I'm sure that simultaneous shutdown of multiple engines is indeed an abort criterion, it's also part of the abort procedure, so disentangling this is kinda tricky.  Based on what Musk said at the press conference, the abort criterion was loaded to trigger the abort based on altitude and/or dynamic pressure data, and the engines were shutdown due to the abort, not the other way around.  Here's the relevant answer in the press conference:

https://www.youtube.com/watch?v=RgPZIwNX7PM?t=4367

I also think you're a bit off on how long the overlap is between the SDs firing and residual thrust from the core.
Just looking at the macro shot of the abort and counting 33 ms video frames (the YouTube version is 1080p), I get the following:

000 ms: First indication that thrust has been cut.
231 ms: First indication of SuperDracos firing.
561 ms: No thrust from F9 core.
825 ms: First motion of D2 away from S2 detectable.

https://www.youtube.com/watch?v=mhrkdHshb3E?t=1163

Finally, it appears that the abort occurs a few seconds after max-q.  That seems weird to me, but maybe you can have the combination of dynamic pressure and wave drag can create more total drag than at max-q.

[envy887]

If these velocities are correct, Falcon accelerated by 4 m/s between abort initiation and separation.

https://twitter.com/Free_Space/status/1220394820574818304

https://twitter.com/Free_Space/status/1220394898937040897

[snotis]

https://twitter.com/Free_Space/status/1220394820574818304

Flight specs from @SpaceX Jan. 18 Crew Dragon Inflight Abort Test: 

Launch escape initiated by special configuration of min-acceleration trigger at 536 m/s, as designed 85 seconds into the flight at 10:31:25 EST

Flawless superdraco burn performance. Peak instantaneous sensed acceleration of 3.3 g, accelerating dragon from 540 m/s (1180 mph) to 675 m/s (1500 mph) in approximately 7 seconds

Falcon telemetry halted at about 11 s after burn, suggesting a comfortable separation distance of about 1500 m (4900 ft) or nearly 1 mile

Peak mach of 2.3
Peak altitude over 40 km (131,000 ft)
Drogue deployment at 5.8 km.
Mains deployment at 2 km.

Final splashdown distance about 42 km east of KSC LC39  at 10:38:54 EST

Does anyone know where this info came from?  Was there a press call earlier today going over this?

[Comga]

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

NASA has now released a higher res version

https://www.flickr.com/photos/nasakennedy/49430129116/

What is all that plumbing sticking out of the SuperDracos?
Post recovery safety, flushing, detanking plumbing?
They have to have something for nominal flights to off-load the propellants that are not used.
That those attach to the engine bells of the SuperDracos seems surprising.

[CorvusCorax]

What is all that plumbing sticking out of the SuperDracos?
Post recovery safety, flushing, detanking plumbing?
They have to have something for nominal flights to off-load the propellants that are not used.
That those attach to the engine bells of the SuperDracos seems surprising.

The SDs are normally covered with a protective cap during handling & launch, which gets ejected when they fire. This would allow potential toxic propellant residue, fumes  or contaminated seawater leak from the engines and attached piping and is a potential risk for ground handling.

Easiest solution: Put plugs in, that prevent foreign objects from getting into, and toxic leftovers from coming out of the nozzles.

I don't have a source for this, though, other than common sense.

[Vettedrmr]

Easiest solution: Put plugs in, that prevent foreign objects from getting into, and toxic leftovers from coming out of the nozzles.

Agreed.  The hi-resolution photo from NASA looks like plugs.

[clongton]

Edit: based on more recent info, it does seem that the abort was initiated by reaching a set speed (and not by detecting loss of thrust as had been speculated),

It's not speculation. The 2 astronauts were interviewed (posted elsewhere on this site) after Elon and Jim and the sequence was discussed as one of the questions. I think it was Bob who said that the detection of loss of thrust was what triggered the abort. And Dragon did not command the Merlins to shut down. That was programmed into the flight computer, located on the upper stage of the Falcon 9.

Edit: It was Doug that said it (8:00 into the interview. Thanks Raul).

[penguin44]

Plug but also kind of look like mounts for a lifting strap