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SpaceX Dragon 2 In Flight Abort Test



 
 
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  #1  
Old January 14th 20, 01:04 PM posted to sci.space.policy
Jeff Findley[_6_]
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Posts: 2,034
Default SpaceX Dragon 2 In Flight Abort Test

Currently the SpaceX Dragon 2 In Flight Abort Test is scheduled for this
Saturday at 8:00 a.m. There is a four hour window for the test. The
reason there is a four hour window is that since it's not going into
orbit, it's not critical they launch "on time". I'm sure this will be
live-streamed by people like @EverydayAstronaut
https://everydayastronaut.com/
https://www.youtube.com/channel/UC6u...J1R2HMTY3LIx5Q

Hopefully it will be on NASA TV and possibly a live stream from SpaceX
as well.

Cites:

SpaceNews.com
SpaceX ready for Crew Dragon in-flight abort test by Jeff Foust
https://spacenews.com/spacex-ready-f...ht-abort-test/

SpaceX on final lap in the commercial crew space race
Rachael Joy, Florida Today
https://www.floridatoday.com/story/t.../01/14/spacexs
-flight-abort-test-final-milestone-before-crewed-flight/2835391001/

Jeff
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These posts do not reflect the opinions of my family, friends,
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  #2  
Old January 15th 20, 03:45 AM posted to sci.space.policy
Greg \(Strider\) Moore
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Posts: 674
Default SpaceX Dragon 2 In Flight Abort Test

"JF Mezei" wrote in message ...

On 2020-01-14 07:04, Jeff Findley wrote:
I'm sure this will be
live-streamed by people like @EverydayAstronaut


Wouldn't SpaceX live stream it? I would expect nothing less than views
from many on-board cameras. A good disaster movie :-)


I assume SpaceX will have a feed. But as I recall @EverydayAstronaut often
has better commentary.


I take it the ejection will happen at MaxQ? At that altitude, can
aircraft assets film the event?


Yes, it will happen at MaxQ.



Will Stage1 come back to land?


Only if any pieces wash up on shore.


What is the impact on Stage1 upon Dragon2 popping out? Is it a
survivable event where Stage1 could cut off engines, start falling and
then aim for the drone ship?


No, this is expected to be a "rapid scheduled disassembly event".

If "firing in the whole" (not really) doesn't break it up, atmospheric
disturbances will.

And if it survives that, hitting the water will ensure an RSDE.

Or does separation happening in "thick" atmosphere result in Stage1
hitting atmosphere in the wrong angle and causing breakup and fireworks?

Or are they actually going to detonate Stage1 prior to the abort and
also test the software/sensors that will automatically trigger the
Dragon abort?


No. We've been over this.




--
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IT Disaster Response -
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  #3  
Old January 15th 20, 01:39 PM posted to sci.space.policy
Jeff Findley[_6_]
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Posts: 2,034
Default SpaceX Dragon 2 In Flight Abort Test

In article ,
says...

On 2020-01-14 07:04, Jeff Findley wrote:
I'm sure this will be
live-streamed by people like @EverydayAstronaut


Wouldn't SpaceX live stream it? I would expect nothing less than views
from many on-board cameras. A good disaster movie :-)

I take it the ejection will happen at MaxQ? At that altitude, can
aircraft assets film the event?


I understand that the abort will actually happen at the time of maximum
drag, which isn't exactly maximum aerodynamic pressure. But, the two
are "close enough" that people just keep saying MaxQ.

Will Stage1 come back to land?


Absolutely not. It will be destroyed by the test. The first stage has
no grid fins or landing legs.

The Falcon 9 first stage will be simulating an abort, which means that
its engines will all shut down. So it will have little control
authority when Dragon 2 aborts. This will expose the (blunt) top of the
2nd stage directly to airflow, including exhaust from the Super Dracos.
This will no doubt cause the booster to tumble. It will therefore break
up quite quickly due to aerodynamic forces because launch vehicles that
are very tall and thin (fineness ratio) are simply not designed to fly
sideways through the air near the portion of the flight where it
experiences maximum aerodynamic pressure.

What is the impact on Stage1 upon Dragon2 popping out? Is it a
survivable event where Stage1 could cut off engines, start falling and
then aim for the drone ship?


See above. Or if you like here's a cite:

SpaceX test-fires rocket ahead of Crew Dragon in-flight abort test
January 11, 2020 Stephen Clark
https://spaceflightnow.com/2020/01/1...cket-ahead-of-
crew-dragon-in-flight-abort-test/

Or does separation happening in "thick" atmosphere result in Stage1
hitting atmosphere in the wrong angle and causing breakup and fireworks?


Again, the top of the 2nd stage will be directly exposed to airflow. It
is simply not designed for this.

Or are they actually going to detonate Stage1 prior to the abort and
also test the software/sensors that will automatically trigger the
Dragon abort?


I don't believe they're going to "detonate" stage 1 because it won't
have a chance to do so. On a crewed flight, the detonation would not be
commanded until after the Dragon 2 has time enough to escape. Falcon
will quite likely be torn apart by aerodynamic forces long before it has
a chance to self destruct.

Falcon 9 does have destruct devices. It also has an automated destruct
system that has been used on uncrewd flights. This article describes
that system:

https://www.floridatoday.com/story/t.../03/11/spacex-
autonomous-flight-safety-system-afss-kennedy-space-center-florida-
falcon9-rocket-air-force-military/98539952/

At the time this article was written, NASA had not yet decided if it
would use the aforementioned automated system on crewed flights. From
the article above:

NASA's Commercial Crew Program is reviewing the system and has
not yet accepted it.

"If done correctly, an automated system is actually safer,
more reliable than having a human in the loop," said Kennedy
Space Center Director Bob Cabana. "We've still got some work
to do before Commercial Crew is going to certify that this
is the way to go, but this is the future."

Cabana, a four-time shuttle astronaut, remembered how
shuttle crews before launches would meet with the Range
safety personnel who could decide their fate.

"We used to go visit the guys that sat on console that
would push the button and show them pictures of our kids
and get to know them," he said.

So, it's not clear to me whether or not crewed Dragon 2 flights will use
the automated system, or whether an actual range safety officer will
have to "push the button".

Jeff
--
All opinions posted by me on Usenet News are mine, and mine alone.
These posts do not reflect the opinions of my family, friends,
employer, or any organization that I am a member of.
  #4  
Old January 16th 20, 01:55 PM posted to sci.space.policy
Jeff Findley[_6_]
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Posts: 2,034
Default SpaceX Dragon 2 In Flight Abort Test

In article ,
says...

On 2020-01-15 07:39, Jeff Findley wrote:

I understand that the abort will actually happen at the time of maximum
drag, which isn't exactly maximum aerodynamic pressure.


is drag different because it includes drag alongside the stage whereas
MaxQ only measures pressure at the tip end of rocket ?


Pretty much.

Absolutely not. It will be destroyed by the test. The first stage has
no grid fins or landing legs.
The Falcon 9 first stage will be simulating an abort, which means that
its engines will all shut down.


Thanks. So at the time the Super Dracos lift Dragon off the stack, the
stack will no longer be producing thrust but still get a lot of drag.


Correct.

From the point of view of testing the worse case scenario, shouldn't the
capsule eject be tested at MaxQ while engines still producing thrust?
Or do all failure scenarios conjured up always involve capsule eject at
time of or after loss of thrust from lower stage?


No. In the case of any abort during first stage burn, the Falcon 9
simultaneously shuts down the engines and sends the "GTFO" signal to
Dragon 2 to initiate its abort. That's one advantage of having a liquid
fueled stage rather than SRBs (which are harder to shut down reliably
without a lot of transient forces being sent through the stack).

So it will have little control
authority when Dragon 2 aborts.


I realize this is moot because any actual abort scenario implicitely
means the lower stage has something very wrong with it, but
**theoretically**, could fins located at the top (front) control
trajectory to keep it "flying" until it has slowed enough to flip and
start to descent engine first? (theoretically)


Again, the 2nd stage isn't designed to handle the loads of being in the
atmosphere without *something* on top of it to handle the aerodynamic
forces. It will likely shred. That will make for quite an
"interesting" environment for the first stage.

Also, if something is "horribly wrong" with the first stage, trying to
land it, either on land in Florida or on the ADS, is "not a good idea".

Or is the speed/air density at that point make it impossible to even
deploy the fins ?


That too. The grid fins on the first stage are designed to deploy in
vacuum *before* first stage reentry. No doubt the actuators don't have
the strength to deploy. Also, even if they did deploy, they'd likely
rip right off anyway.

This will expose the (blunt) top of the
2nd stage directly to airflow, including exhaust from the Super Dracos.


Assuming for a second a more or less intact Stage 1, would the exhaust
from the Super Dracos compromise the top of Stage 1's tank and cause
some pretty fireworks? Or is the direction of the escape engines exhaust
such that impingement onto the top of Stage 1's tanks won't happen?


Again, you're forgetting there is a fully fueled *second stage* between
the two. Falcon 9 ain't an SSTO. Remember how Challenger was ripped
apart by aerodynamic forces? That's what's going to happen on this
abort to both the first and second stages of Falcon 9.

I don't believe they're going to "detonate" stage 1 because it won't
have a chance to do so.


If the trigger is shutdown of engines, then there is no need to detonate
it. Hopefully we get nice footage of the stage as it starts to veer off
course and eventually breaks off.


I'd imagine that events will unfold very quickly. Again, remember what
happened to Challenger. It ripped apart in seconds.

In the event of rocket veering off course and aiming for the White
House, when it leaves it cone of normal flight, what order are commands?

Shutdown engines, initiate eject, initiate range safety? (with shutdown
of engines possibly not happening)


First two happen simultaneously. Range safety likely comes later. NASA
and SpaceX would know the details (likely dictated by NASA for crew
safety).

Also, engine shutdown *will* happen. If you rip the engine control
module from a modern car, the engine doesn't keep running. It's a
necessary component to keep it going. A liquid fueled rocket engine
should be much the same. Absent being commanded to "keep going", I'd
imagine valves are designed to "fail safe", which means shutting the
thing down.

NASA's not going to crew rate any vehicle that doesn't have a way to
reliably terminate thrust. For liquids, that's relatively easy to
design into the system.

Shutdown engines, initiate range safety, and initiate capsule eject?


No.

Or would it be just capsule eject and then range safety ?


Yes.

Jeff
--
All opinions posted by me on Usenet News are mine, and mine alone.
These posts do not reflect the opinions of my family, friends,
employer, or any organization that I am a member of.
 




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