A Space & astronomy forum. SpaceBanter.com

If this is your first visit, be sure to check out the FAQ by clicking the link above. You may have to register before you can post: click the register link above to proceed. To start viewing messages, select the forum that you want to visit from the selection below.

Go Back   Home » SpaceBanter.com forum » Space Science » Policy
Site Map Home Authors List Search Today's Posts Mark Forums Read Web Partners

SpaceX Dragon 2 capsule destroyed in abort motor ground test



 
 
Thread Tools Display Modes
  #11  
Old April 25th 19, 11:49 PM posted to sci.space.policy
Fred J. McCall[_3_]
external usenet poster
 
Posts: 10,018
Default SpaceX Dragon 2 capsule destroyed in abort motor ground test

"Rocket Man" wrote on Thu, 25 Apr 2019
11:02:13 +0200:


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


No, it's not. When SpaceX knows something they will say it. Until
then there's nothing to say.


--
"Some people get lost in thought because it's such unfamiliar
territory."
--G. Behn
Ads
  #12  
Old April 26th 19, 11:35 AM posted to sci.space.policy
Jeff Findley[_6_]
external usenet poster
 
Posts: 1,973
Default SpaceX Dragon 2 capsule destroyed in abort motor ground test

In article ,
says...

On 2019-04-25 18:49, Fred J. McCall wrote:

No, it's not. When SpaceX knows something they will say it. Until
then there's nothing to say.


They haven't receleased video of the event, nor of the state of the
capsule after the event. These are facts they know.


Boeing has not released video of its anomaly during its ground test of
its liquid fueled abort system. Reportedly there was a leak. NASA
knows how bad it was. But the public, not so much. This is part of the
commercial nature of the contracts. Anything that can be considered a
trade secret can't (easily) be released by NASA as it could give the
competition insight into the design and how it works.

In the past, Musk had built expectations to see videos even of stuff
that doesn't quite go right.


That was mostly Falcon 9 landing tests. As the head of the company,
that's his call to release those videos. Besides, a Falcon 9 landing
will never endanger people. Commercial crew is a bit different.

(In the rocket that exposded at pad, it was enthousisats who released
videos, not SpaceX, so there is precedent of SpaceX not releasing video
of a catastrophic failure.


Likely a cell phone video. Could have been someone at NASA, who was
observing the test. Their entire account on YouTube has since been
deleted. That's telling (i.e. someone is in hot water with their
bosses).

I suspect SpaceX decided that allowing speculation of what happened is
better than confirming what happened. Have to wonder if SpaceX' hands
may be bound because this is a NASA contract/hardware.


They've decided not to release information until they've come to the
conclusion what caused the anomaly. This is quite normal for an
investigation of this type. However, that does not stop armchair
engineers from speculating, now does it?

Either way, they will at one point have to release details of the
accident prior to resuling flight because NASA doesn't want to be seen
flying something which the public might deeem to be unsafe.


They'll most likely release the details once the actual cause is known.
Right now they're surely busy cleaning up the site, cataloging the
debris, and investigating the cause. These things take time.

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.
  #13  
Old April 26th 19, 03:33 PM posted to sci.space.policy
Fred J. McCall[_3_]
external usenet poster
 
Posts: 10,018
Default SpaceX Dragon 2 capsule destroyed in abort motor ground test

JF Mezei wrote on Fri, 26 Apr 2019
02:19:47 -0400:

On 2019-04-25 18:49, Fred J. McCall wrote:

No, it's not. When SpaceX knows something they will say it. Until
then there's nothing to say.


They haven't receleased video of the event, nor of the state of the
capsule after the event. These are facts they know.


They have better things to do than fuel a bunch of harassed
speculation. Neither of the things you list are 'facts' and the
second one probably isn't even true.


In the past, Musk had built expectations to see videos even of stuff
that doesn't quite go right.


Yes, yes, you were frightened by Musk when you were little. We get
it.


(In the rocket that exposded at pad, it was enthousisats who released
videos, not SpaceX, so there is precedent of SpaceX not releasing video
of a catastrophic failure.


Again for the totally clueless among us, SpaceX will undoubtedly
release video when they can explain what is going on in it.


I suspect SpaceX decided that allowing speculation of what happened is
better than confirming what happened.


Showing you a video with no explanation doesn't 'confirm' anything.


Have to wonder if SpaceX' hands
may be bound because this is a NASA contract/hardware.


Silly idea.


Either way, they will at one point have to release details of the
accident prior to resuling flight because NASA doesn't want to be seen
flying something which the public might deeem to be unsafe.


Yes, they will, and that's when they'll do it. When they can explain
what happened.


--
"Some people get lost in thought because it's such unfamiliar
territory."
--G. Behn
  #14  
Old April 27th 19, 07:06 AM posted to sci.space.policy
Fred J. McCall[_3_]
external usenet poster
 
Posts: 10,018
Default SpaceX Dragon 2 capsule destroyed in abort motor ground test

JF Mezei wrote on Fri, 26 Apr 2019
22:49:33 -0400:

On 2019-04-26 06:35, Jeff Findley wrote:

Likely a cell phone video.


As I recall they were enthousists wioth 60fps camera on tripiod filming
the whole thing. so unlikely to be cellphone. (storage, battery autonomy).


I don't think you're aware of the capabilities of cell phones.

Their entire account on YouTube has since been
deleted. That's telling (i.e. someone is in hot water with their
bosses).


That is very sad. Especially since it is a case closed, and as I recll,
even SpaceX was happy to get the original video to give it an additional
point of view.


Just how is it a 'case closed'?

They've decided not to release information until they've come to the
conclusion what caused the anomaly.


If you look at NTSB and similar agencies, they will generally quickly
release facual information and early photos of wreckage (ensuring no
clue to cause is seen in photos). But they will show extent of destruction.


This isn't a passenger airplane crash and SpaceX isn't NTSB.

investigation of this type. However, that does not stop armchair
engineers from speculating, now does it?


It makes it worse.


Not possible.


Consider TWA800 where they didn't want to release any info, ...


You mean where they didn't HAVE any info.


... which lead
to speculation ranging from space aliens attacking it to terrorism.


There are still loons insisting that the report is a cover up and that
the Navy shot it down.


When Swissair 111 came down, the Canadian government didn't want to
repeat this and made sure they released as much info as they could
regularly. And that really reduced speculation on what caused it.
This has since been seen in more air crashes.


They had info.

They'll most likely release the details once the actual cause is known.
Right now they're surely busy cleaning up the site, cataloging the
debris, and investigating the cause. These things take time.


Is this a SpaceX investigation or a NASA investigation?


Yes. SpaceX will have the lead, since it's their vehicle.


--
"Some people get lost in thought because it's such unfamiliar
territory."
--G. Behn
  #15  
Old April 29th 19, 03:13 AM posted to sci.space.policy
Fred J. McCall[_3_]
external usenet poster
 
Posts: 10,018
Default SpaceX Dragon 2 capsule destroyed in abort motor ground test

JF Mezei wrote on Sun, 28 Apr 2019
15:54:17 -0400:

Have no idea if this is legit of not.

video on the Dragon "anomaly"

https://www.youtube.com/watch?v=6whBllkTkuU

At about 55 second mark, includes phone video from futuremartian97
which allegedly shows the spaceX Dragon2 abort test. In it, it is pretty
clear the capsule goes kablouey big time.


Uh, no. There is no 'abort test'. The abort test is what they were
working their way toward several months from now.


(On youtube, you can use . and , to go frame by frame (. = forward, , =
backward).

There is not enough detail in those explosion frames to know if this
video is legit or not.

IF legit, this video shows capsule explosion happening before exhaust is
seen out of engines.


Which doesn't tell you anything at all.


--
"Insisting on perfect safety is for people who don't have the balls to
live in the real world."
-- Mary Shafer, NASA Dryden
  #16  
Old April 29th 19, 02:01 PM posted to sci.space.policy
David Spain
external usenet poster
 
Posts: 2,565
Default SpaceX Dragon 2 capsule destroyed in abort motor ground test

On 4/22/2019 7:05 AM, Jeff Findley wrote:

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


FWIW the conventional wisdom seems to be focusing on the COPV tanks used
to fuel the SuperDracos. But this is pure speculation (SWAGs if you
will). I have seen ONE still frame taken from a normal speed camera that
appears to show an explosion taking place "around" the capsule where the
hatch window still appears in the frame. In another video you can see at
least two explosions, the first as mentioned where the capsule is
largely still intact and a 2nd to the left (from the viewer viewpoint)
of the first which appears to blow the capsule off the test stand. Which
would tend to indicate multiple possibly cascading explosions.

AFAIK know from what has been published in other forums the capsule is
believed to be a total loss.

Yes this is bad, but the test engineer in me is very happy that this
happened during *testing*. Although a RUD is never a welcome event it is
a learning opportunity with the net result of an improved design. This
is what happened after the Apollo 1 fire. The following block
improvements to the Command Module made the follow-ons very different
from the original article including the wiring and hatch design from
what I have read. It was poor judgement and bad test design that I feel
were the real reason behind the fatalities that should not have happened.

You could say we were "lucky" that this happened while no crew were
on-board, but I *hate* that term. What is proper to say is that an
anomaly was caught in testing, just as it should be. What keeps me up at
night are the anomaly's that I didn't test for. That is why you do
design review after design review and test and test again, and then
alter and add to the testing regimen and test again to prove out design
margins.

Luck as defined simply means you missed a test and found a failure mode
at an opportune time.

David

  #17  
Old April 29th 19, 02:38 PM posted to sci.space.policy
Fred J. McCall[_3_]
external usenet poster
 
Posts: 10,018
Default SpaceX Dragon 2 capsule destroyed in abort motor ground test

JF Mezei wrote on Sun, 28 Apr 2019
23:11:19 -0400:

On 2019-04-28 22:13, Fred J. McCall wrote:

Uh, no. There is no 'abort test'. The abort test is what they were
working their way toward several months from now.


IsN't capsule jettison an "abort" test ? If not sorry for bad terminology.


There was no 'capsule jettison' as part of this engine test sequence.
There are two abort cases they really want to test (the two are at the
extremes of the envelope). One is a 'ground abort', where the capsule
needs to escape before or very near after liftoff. That test was
completed years ago. The other case is a 'Max Q' abort, where the
capsule separates and escapes when the stack is undergoing maximum
aerodynamic pressure. That's the one they're working toward doing.
The test with the anomaly involved a restrained capsule firing engines
just as an engine test.

IF legit, this video shows capsule explosion happening before exhaust is
seen out of engines.


Which doesn't tell you anything at all.


Not seeing exhaust from Super Dracos before explosion seems to be
significant to me. Bas there been say 2 seconds of exhaust and SpaceX
telemetry shwhoing "take off " force of the capsule against its stand
and then kaboom, it woudl mean that engines started and produced thrust
before things went wrong.


It may seem 'significant' to you, but it shouldn't.


If the kaboom happens before that, it would point to the explosion
happening prior to the hypergolics mixing in the combustion chamber and
then goig out the exhaust.


You don't know that. For example, one hypothetical failure that would
look like what is seen would be a catastrophic combustion chamber
failure right when the propellents mix.


What is not known is the time delay between the command to strt engines
and the explosion. If 10 seconds elapsed between command and explision
with engines showing no sign of thrust, it is quite different from a big
kaboom happening within a second of command being sent.


You can flap your arms all you like but you can't come up with a
hypothesis that will fly without a LOT more data (and there are a lot
more things that aren't known than the one you cite).


For hypergolic fuels, do any of the 2 components have ability to ignite
without the other component when in contact with air ? Or are they truly
inert until the 2 components meet ? (aka: could combination of spark and
ambient air with O2 in it cause one of the 2 to ignite ?) Or does the
explosion imply that the 2 components did meet/mix ?


You can get hydrazine to oxidize in air, but it won't be nearly as
energetic as when oxidized with dinitrogen tetroxide. For example,
hydrazine is used as a foam blowing agent because of the huge
quantities of gas it produces during normal oxidation. The question
is where would air and a spark come in contact with gaseous hydrazine?
I consider it unlikely in the extreme. I'd consider the likely causes
here to be a pressure vessel or pressure line failure or a combustion
chamber failure. I'm sure there are lots of other possible failure
modes.


--
"Insisting on perfect safety is for people who don't have the balls to
live in the real world."
-- Mary Shafer, NASA Dryden
  #18  
Old April 30th 19, 03:28 AM posted to sci.space.policy
Fred J. McCall[_3_]
external usenet poster
 
Posts: 10,018
Default SpaceX Dragon 2 capsule destroyed in abort motor ground test

David Spain wrote on Mon, 29 Apr 2019 09:01:20
-0400:


FWIW the conventional wisdom seems to be focusing on the COPV tanks used
to fuel the SuperDracos.


Possible, but this seems odd to me. Neither of the fuels is even
mildly cryogenic, so what failure mode would there be? This isn't
like the Falcon 9 explosion where cryogenic chilling was involved. If
it was something like that I would expect it would have to be a 'one
off' manufacturing defect of some kind, which would lead to a pretty
rapid return to flight.


--
"Insisting on perfect safety is for people who don't have the balls to
live in the real world."
-- Mary Shafer, NASA Dryden
  #19  
Old April 30th 19, 03:40 AM posted to sci.space.policy
Fred J. McCall[_3_]
external usenet poster
 
Posts: 10,018
Default SpaceX Dragon 2 capsule destroyed in abort motor ground test

JF Mezei wrote on Mon, 29 Apr 2019
17:00:46 -0400:

On 2019-04-29 09:38, Fred J. McCall wrote:

I consider it unlikely in the extreme. I'd consider the likely causes
here to be a pressure vessel or pressure line failure or a combustion
chamber failure. I'm sure there are lots of other possible failure
modes.



Would the hypergolic tanks need to be highly pressurized? What is
needed is for the liquid components be pushed through pipes to
combustion chamber right?


Right, which means you need pressure that exceeds the combustion
chamber pressure. That implies either highly pressurized tanks,
really powerful pumps, or both. It's usually done with highly
pressurized tanks because that's the simpler approach (fewer moving
parts) and the point behind hypergolic engines is simplicity and
reliability.


How would the hypergolic tanks be configured? are they like a piston,
normally with no pressure, but when needed, helium is pushed on one side
of piston to push the fuel out the other end ? or just pumping helium
into the bank hoping the fuel is at the "exit" end ? Are the tanks
normally under pressure or is pressure applied only when engines are fired ?


My expectation would be that the tanks would always be pressurized and
that engine firing is controlled by throttle valves. Again, simplest
and most reliable approach.


We may have seen an explosion, but it has no context in terms of
timeline. Were they filling tanks? did explosion happen while noting was
happening? or happen when they fired the engines ?


Exactly the point. Since they were going into an engine test I'd
expect the tanks would already be filled long before. Again, these
are not cryogenic fluids and there's not a "we want them as cold as
possible". Remember, in normal use these tanks may sit for a LONG
time before the engines get used, since they're not normally using
during an ascent. I'd expect the explosion happened either very
shortly before or right at 'engine ignition' time.


This may have nothing to do with actual engines. It it may.


I find it doubtful that there is a systemic design flaw with all the
fire time that these engines have had. I'm leaning toward a 'one off'
manufacturing flaw or mechanical failure involving a pressure vessel,
tank, feed line, or combustion chamber. But I don't know any more
than anyone else, not having the exact timeline and telemetry.


--
"Insisting on perfect safety is for people who don't have the balls to
live in the real world."
-- Mary Shafer, NASA Dryden
  #20  
Old April 30th 19, 03:49 AM posted to sci.space.policy
David Spain
external usenet poster
 
Posts: 2,565
Default SpaceX Dragon 2 capsule destroyed in abort motor ground test

On 4/29/2019 10:28 PM, Fred J. McCall wrote:
David Spain wrote on Mon, 29 Apr 2019 09:01:20
-0400:


FWIW the conventional wisdom seems to be focusing on the COPV tanks used
to fuel the SuperDracos.


Possible, but this seems odd to me. Neither of the fuels is even
mildly cryogenic, so what failure mode would there be? This isn't
like the Falcon 9 explosion where cryogenic chilling was involved. If
it was something like that I would expect it would have to be a 'one
off' manufacturing defect of some kind, which would lead to a pretty
rapid return to flight.



Let's hope so. Could be a weld issue? Could be a lot of things I
suppose. If these things are made in batches it might be informative to
pull COPV's from the same build run and check them, maybe run some
stress tests on them. It's all SWAG at this point and I'm sure as hell
no expert. Could be something else entirely. Conventional wisdom is
often wrong.

Dave

 




Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

vB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
SpaceX gets paid for Pad Abort test Greg \(Strider\) Moore Policy 2 June 12th 15 12:46 AM
SpaceX Dragon Capsule Splashes Down in Pacific, Ending Historic Test Flight [email protected] Policy 11 June 4th 12 02:22 PM
Dragon capsule parachute test Pat Flannery Policy 60 September 24th 10 03:51 AM
Dragon capsule parachute test Craig Bingman History 0 September 24th 10 03:51 AM
Dragon capsule parachute test Dr J R Stockton[_79_] History 0 August 27th 10 11:37 PM


All times are GMT +1. The time now is 11:45 AM.


Powered by vBulletin® Version 3.6.4
Copyright ©2000 - 2019, Jelsoft Enterprises Ltd.
Copyright 2004-2019 SpaceBanter.com.
The comments are property of their posters.