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SpaceX Dragon 2 capsule destroyed in abort motor ground test



 
 
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  #1  
Old April 22nd 19, 12:05 PM posted to sci.space.policy
Jeff Findley[_6_]
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Default SpaceX Dragon 2 capsule destroyed in abort motor ground test


Accident Claims SpaceX Dragon Abort Test Capsule
Apr 21, 2019 Irene Klotz - Aerospace Daily & Defense Report
https://aviationweek.com/space/accid...on-abort-test-
capsule

This is bad. My guess is at least a year delay for SpaceX commercial
crew. Here is hoping that Boeing gets its act together because we need
something to replace Soyuz for US crew.

Jeff
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  #2  
Old April 22nd 19, 09:06 PM posted to sci.space.policy
Fred J. McCall[_3_]
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Default SpaceX Dragon 2 capsule destroyed in abort motor ground test

Jeff Findley wrote on Mon, 22 Apr 2019
07:05:42 -0400:


Accident Claims SpaceX Dragon Abort Test Capsule
Apr 21, 2019 Irene Klotz - Aerospace Daily & Defense Report
https://aviationweek.com/space/accid...t-test-capsule

This is bad. My guess is at least a year delay for SpaceX commercial
crew. Here is hoping that Boeing gets its act together because we need
something to replace Soyuz for US crew.


I don't know if we know enough to be talking about how much delay this
would inject. The headline makes it sound like the capsule is a dead
loss but I don't think we even know that for sure.


--
"Insisting on perfect safety is for people who don't have the balls to
live in the real world."
-- Mary Shafer, NASA Dryden
  #3  
Old April 23rd 19, 05:55 PM posted to sci.space.policy
Rocket Man[_2_]
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Posts: 8
Default SpaceX Dragon 2 capsule destroyed in abort motor ground test


"Fred J. McCall" wrote in message
...
Jeff Findley wrote on Mon, 22 Apr 2019
07:05:42 -0400:


Accident Claims SpaceX Dragon Abort Test Capsule
Apr 21, 2019 Irene Klotz - Aerospace Daily & Defense Report
https://aviationweek.com/space/accid...t-test-capsule

This is bad. My guess is at least a year delay for SpaceX commercial
crew. Here is hoping that Boeing gets its act together because we need
something to replace Soyuz for US crew.


I don't know if we know enough to be talking about how much delay this
would inject. The headline makes it sound like the capsule is a dead
loss but I don't think we even know that for sure.


It looked to me that the capsule had dissappeared after the explosion. Not
good. Not good at all.

I agree with OP that this could take a year to fix, not to mention the loss
of goodwill. I can imagine the knifes are being drawn in Congress. I'm sure
this is exactly the thing Boeing / LockMart / ULA have been waiting for.

OTOH it would've been infinitely worse if it had happened during a manned
test flight.


  #4  
Old April 23rd 19, 10:36 PM posted to sci.space.policy
Fred J. McCall[_3_]
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Posts: 10,018
Default SpaceX Dragon 2 capsule destroyed in abort motor ground test

JF Mezei wrote on Mon, 22 Apr 2019
20:34:34 -0400:

On 2019-04-22 07:05, Jeff Findley wrote:

Accident Claims SpaceX Dragon Abort Test Capsule
Apr 21, 2019 Irene Klotz - Aerospace Daily & Defense Report
https://aviationweek.com/space/accid...on-abort-test-
capsule


(sorry, it won't allow me to read that article).


You have to take the line break out so that it ends with '-capsule'.


Saw pictures of people on a beach with the big orange cloud at a
distance. How dangerous is burned hydrazine ? or would that cloud
contain unburned toxig hypergolics ?


Hydrazine burns to nitrogen and water. The color sounds to me like
nitrogen dioxide, which is a partial decomposition product of
dinotrogen tetroxide. Hydrazine and dinitrogen tetroxide are both
colorless.


I assume thrusters on shuttle were a simple pump that pushed the 2
compienst into a small chamnber where they mix, combust and then push
themselves out through the thruster port.

Would Draco be the same or have actual turbopumps and high
velocity/energy moving parts ?


First, it's SuperDraco, not Draco. SuperDraco is something like 200
times the size of Draco. Most hypergolic engines use simple pumps,
although turbopumps are possible in very large engines. SuperDraco
uses ordinary pumps.


Are the hypergolic tanks highly pressurized or just enough to push the
liquids to the combustion chamber ?


They're usually pressurized to above the chamber pressure of the
engine.


Trying to understand what sort of failure mode would cause the apparent
total destruction of the craft.


We don't know that there WAS "total destruction of the craft".


If the engines are simple pumps that push the hypergolics into chamnber
and they burn and exhaust, why would salt water cause such a failure?


Where did you get the idea that salt water had anything to do with it?
The engines successfully fired multiple times before the 'anomaly'.


If the engines are more complex with turbopumps and what not, wouldn't
they require fairly expensive inspections before being fired ?


They aren't and no, why would they?


If they find out that the cause of the accident was salt water, could
this allow "on time" continuation of programme using a new Dragon 2 as
test article for the pad eject test ? (aka: delay re-usability but don't
delay programme).


If they find out the cause of the anomaly WHATEVER IT WAS they will
then be able to continue the program. It looks to me like a pump
failure on the hydrazine tank, but that's just a guess and we don't
know why it failed if that was the case.


Or does this accident represent a hard stop to the programme
irrespective of cause until Space-X has designed changes to the
capsule/engines and proven it is safe to NASA ?


Regardless of the cause they are at full stop until they determine
what the cause was. They will then have to prove it's safe,
regardless of whether they have to make changes or not. There's a lot
of fire time on SuperDraco engines for me to believe there is some
fundamental design flaw.


Is it correct to assume that SpaceX would have tested engines after
having dropped them in sea water well before building the first Dragon 2
capsule ?


No, it is not, because there is no reason to do so.


--
"Some people get lost in thought because it's such unfamiliar
territory."
--G. Behn
  #5  
Old April 24th 19, 07:06 AM posted to sci.space.policy
Fred J. McCall[_3_]
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Posts: 10,018
Default SpaceX Dragon 2 capsule destroyed in abort motor ground test

JF Mezei wrote on Tue, 23 Apr 2019
17:51:41 -0400:

On 2019-04-23 12:55, Rocket Man wrote:

It looked to me that the capsule had dissappeared after the explosion. Not
good. Not good at all.


Consider that rocket that was being test fueled and which exploded "for
no reason". SpaceX was fairly quick to isolate this to the filling
sequence of helium vs surrounding liquid oxyggen which caused
unpredicted behaviour of COPV tanks.


Why would I consider that? You're comparing apples and aardvarks.


Reverting to previous , proven filling sequence allowed return to flight
fairly quickly. Not sure if SpaceX later changed the COPV tanks to allow
the more desirable filling sequence or not, but if it did, it happened
in a transparent way without delaying the launches.


They changed the tank.


So the fact that the capsule was allegedly blown to smithereens


Got a cite for that? Who is 'alleging' this?


shouldn't be an indication of how long it will take to get back in
business. It all depends on whether they can find the cause and if this
is a simple fix. (or simple to avoid the use in a way that causes it to
go "kaboom".


It still comes down to, as I said, figuring out what the root cause
was.


One should also remember this capsule was being re-used, it wasn't brand
new. So the problem may be one of re-usability and not one of
design/safety for new ones.


What one should remember is that one doesn't go into a root cause
analysis with preconceived notions.


I would assume that they have high quality video of what happened as
well as lots of telemetry.


Probably a fair assumption.

I agree with OP that this could take a year to fix, not to mention the loss
of goodwill.


They've done engine tests before. Did they test engines after being
dunked in salt water?


I doubt it as there's no reason to do so.


Did they test engines after being in space
environment (temperature changes) ?


I would assume there were some 'shake and bake' tests for vibration
and temperature extremes.


I have to assume that when they
chose the materials used to 3d print the engines, they considered and
tested ability to survive the temperature extremes and vibration from
launch and salt water.


You seem to be assuming the entire engine was 3D printed. I don't
think that's the case. I believe it was only the combustion chamber
that was 3D printed. I'm pretty sure they didn't build it out of
styrofoam.


If the engines are deemed to not be re-usable, then SpaceX can operate
Dragon-2 as non-reusable at first,or perhaps always install new super
dracos before re-use if rest of capsule is reusable.


You are way, WAY ahead of yourself. There is no reason to leap to
your apparent assumption that it is something to do with
'reusability'. Hypergolic engines are simple and reliable and can be
restarted hundreds of times. It's the nature of the breed. You seem
to forget that the engines had already fired multiple times in this
test sequence before the anomaly occurred.


I can imagine the knifes are being drawn in Congress. I'm sure
this is exactly the thing Boeing / LockMart / ULA have been waiting for.


SpaceX has launched to the station aleady. So still ahead of Boeing.


That depends on just how long they have to stand down.


--
"Insisting on perfect safety is for people who don't have the balls to
live in the real world."
-- Mary Shafer, NASA Dryden
  #6  
Old April 24th 19, 10:57 AM posted to sci.space.policy
[email protected]
external usenet poster
 
Posts: 7
Default SpaceX Dragon 2 capsule destroyed in abort motor ground test

Hi all

Has anyone seen any official news or information from SpaceX themselves? Their website hasn't yet been updated (last I checked). Not exactly something that you want splashed all over the front pages, but then again they have been amazingly open about previous failures.

On an aside, assuming a total vehicle loss from this "anomaly" how soon will the next test article be available? Does SpaceX have a couple of capsules waiting or was this the only one?

Regards
Frank
  #8  
Old April 24th 19, 12:12 PM posted to sci.space.policy
Jeff Findley[_6_]
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Posts: 2,008
Default SpaceX Dragon 2 capsule destroyed in abort motor ground test

In article ,
says...

JF Mezei wrote on Mon, 22 Apr 2019
20:34:34 -0400:

On 2019-04-22 07:05, Jeff Findley wrote:

Accident Claims SpaceX Dragon Abort Test Capsule
Apr 21, 2019 Irene Klotz - Aerospace Daily & Defense Report
https://aviationweek.com/space/accid...on-abort-test-
capsule


(sorry, it won't allow me to read that article).


You have to take the line break out so that it ends with '-capsule'.


Saw pictures of people on a beach with the big orange cloud at a
distance. How dangerous is burned hydrazine ? or would that cloud
contain unburned toxig hypergolics ?


Hydrazine burns to nitrogen and water. The color sounds to me like
nitrogen dioxide, which is a partial decomposition product of
dinotrogen tetroxide. Hydrazine and dinitrogen tetroxide are both
colorless.


I guessed it was a BFRC (big falcon red cloud) from the nitrogen
tetroxide converting to nitrogen dioxide. The picture on Wikipedia
shows some nice orange to red colors:

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

I assume thrusters on shuttle were a simple pump that pushed the 2
compienst into a small chamnber where they mix, combust and then push
themselves out through the thruster port.

Would Draco be the same or have actual turbopumps and high
velocity/energy moving parts ?


First, it's SuperDraco, not Draco. SuperDraco is something like 200
times the size of Draco. Most hypergolic engines use simple pumps,
although turbopumps are possible in very large engines. SuperDraco
uses ordinary pumps.


As far as I know, SuperDraco doesn't use pumps (too heavy and slow).
It's a "simple" pressure fed system. But because of the flow rates and
thrust needed in a short amount of time, I'd imagine that the helium
tanks for them are extremely high pressure and the valves and lines are
sized for high flow rates.

Are the hypergolic tanks highly pressurized or just enough to push the
liquids to the combustion chamber ?


They're usually pressurized to above the chamber pressure of the
engine.


Yep.


Trying to understand what sort of failure mode would cause the apparent
total destruction of the craft.


We don't know that there WAS "total destruction of the craft".


All we know, from the clearly unauthorized cell phone video, is that the
spacecraft was out of frame at the end of the video. It's not like it
was a high speed camera. The Dragon 2 capsule could be sitting on the
ground just out of frame or it could be in little pieces. The fact is
that we just don't know.

If the engines are simple pumps that push the hypergolics into chamnber
and they burn and exhaust, why would salt water cause such a failure?


Where did you get the idea that salt water had anything to do with it?
The engines successfully fired multiple times before the 'anomaly'.


That is still unclear. Some things I've read online say that they
earlier tests that day were of the Draco engines. That would mean that
the SuperDraco test at the end would have been the first time they were
fired since the DM-1 mission (where they were not used, but were
subjected to a spaceflight and ocean water landing).

If the engines are more complex with turbopumps and what not, wouldn't
they require fairly expensive inspections before being fired ?


They aren't and no, why would they?


Pressure fed engines with hypergolic propellants so they're as simple,
and reliable, as they can be. Every US crewed spacecraft following
Mercury has used similar engines.

If they find out that the cause of the accident was salt water, could
this allow "on time" continuation of programme using a new Dragon 2 as
test article for the pad eject test ? (aka: delay re-usability but don't
delay programme).


If they find out the cause of the anomaly WHATEVER IT WAS they will
then be able to continue the program. It looks to me like a pump
failure on the hydrazine tank, but that's just a guess and we don't
know why it failed if that was the case.


From the crappy video, it almost looks like a helium pressure vessel,
valve, or line ruptured first followed by the nitrogen tetroxide and
hydrazine tanks rupturing. What little burning did occur would be what
spread the cloud of propellants into the atmosphere (this cloud showed
up on weather radar!).

Or does this accident represent a hard stop to the programme
irrespective of cause until Space-X has designed changes to the
capsule/engines and proven it is safe to NASA ?


Regardless of the cause they are at full stop until they determine
what the cause was. They will then have to prove it's safe,
regardless of whether they have to make changes or not. There's a lot
of fire time on SuperDraco engines for me to believe there is some
fundamental design flaw.



Agreed. But in the meantime, preparations continue for the next Dragon
cargo flight to ISS. This should not be a concern since Dragon has no
SuperDraco engines and Dragon has been flight proven many times over.

Is it correct to assume that SpaceX would have tested engines after
having dropped them in sea water well before building the first Dragon 2
capsule ?


No, it is not, because there is no reason to do so.


Actually, the Dragon 2 pad abort test capsule was recovered from the
ocean and later used as the DragonFly test article (which performed
tethered hover tests on its SuperDraco engines).

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.
  #9  
Old April 24th 19, 12:19 PM posted to sci.space.policy
Jeff Findley[_6_]
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Posts: 2,008
Default SpaceX Dragon 2 capsule destroyed in abort motor ground test

In article ,
says...

Hi all

Has anyone seen any official news or information from SpaceX
themselves? Their website hasn't yet been updated (last I
checked). Not exactly something that you want splashed all
over the front pages, but then again they have been amazingly
open about previous failures.


Nope, nothing "official" as far as I know. There was an initial
statement saying they were investigating with NASA, but that's it.

On an aside, assuming a total vehicle loss from this "anomaly"
how soon will the next test article be available? Does SpaceX
have a couple of capsules waiting or was this the only one?


NASA wanted new capsules for each flight to ISS, so I believe that the
capsule which was to be used for the first crewed flight to ISS is
pretty much ready to fly. I have no idea how far along other capsules
are, but I've got to believe they have several others in various stages
of assembly.

Flown Dragon 2 capsules are planned to be used for commercial cargo
missions to ISS. I understand that before they are used as cargo
vehicles, their SuperDraco engines (and presumably tanks and plumbing)
will be removed so that the capsule will have more cargo mass capacity.

But in the meantime, SpaceX has been refurbishing flown Dragon capsules
for commercial cargo missions to ISS. So I would think that they could
keep doing that in the absence of flown Dragon 2 capsules.

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.
  #10  
Old April 25th 19, 10:02 AM posted to sci.space.policy
Rocket Man[_2_]
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Posts: 8
Default SpaceX Dragon 2 capsule destroyed in abort motor ground test


Isn't that the same everywhere these days? Bad news gets brushed under the
carpet whilst good news is trumpeted everywhere.

Do you guys remember the failed landing of Sierra Nevada's DreamChaser where
it tumbled over on landing. They never released the footage, citing that it
wasn't relevant.


 




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