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
  #21  
Old April 30th 19, 07:04 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 Tue, 30 Apr 2019
01:09:47 -0400:

Does Dragon-2 have single fuel and pressuriation system to serve all
Draco and Super Draco engines ?


I doubt it. The SuperDracos are 'podded' in pairs and each pair is
independent from all the others.


Much of the text I read says stuff such as "use the same propellants"
which could either mean they use the same type of fuel, or that they
draw propellands from the same tanks. Hence question.


I think each pair of SuperDracos has its own propel lent tanks and
pressurization system.


Since the system worked for the Dracos during flight, one would want to
look at what is different when you need the Super Dracos. (Or perhaps
for the succesfull flight, the pressurized it only to the pressure
needed by Dracos, knowing SuperDracos would not be used).


I'm pretty sure they're totally independent. The pairs of SuperDracos
are fully independent from each other.


--
"Insisting on perfect safety is for people who don't have the balls to
live in the real world."
-- Mary Shafer, NASA Dryden
Ads
  #22  
Old April 30th 19, 07:05 PM posted to sci.space.policy
Jeff Findley[_6_]
external usenet poster
 
Posts: 2,057
Default SpaceX Dragon 2 capsule destroyed in abort motor ground test

In article ,
says...

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.


You're going to get little to no actual useful information from a cell
phone video. It's way too low frame rate and the way they respond to
rapid changes in light pretty much means you can't trust the few frames
you have.

NASA and SpaceX no doubt have access to high speed video of the test.
Just wait for the investigation to complete and see what they find.
Idle speculation based on bad information isn't helping.

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.
  #23  
Old April 30th 19, 07:08 PM posted to sci.space.policy
Jeff Findley[_6_]
external usenet poster
 
Posts: 2,057
Default SpaceX Dragon 2 capsule destroyed in abort motor ground test

In article , says...

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.


I agree with all of this.

Also, from what I understand, there is a list of safety related issues
that NASA wanted SpaceX to take care of before flying crew on DM-2. The
other "silver lining" is that this gives SpaceX more time to take care
of those issues as well.

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.
  #24  
Old April 30th 19, 07:10 PM posted to sci.space.policy
Jeff Findley[_6_]
external usenet poster
 
Posts: 2,057
Default SpaceX Dragon 2 capsule destroyed in abort motor ground test

In article ,
says...

JF Mezei wrote on Tue, 30 Apr 2019
01:09:47 -0400:

Does Dragon-2 have single fuel and pressuriation system to serve all
Draco and Super Draco engines ?


I doubt it. The SuperDracos are 'podded' in pairs and each pair is
independent from all the others.


Much of the text I read says stuff such as "use the same propellants"
which could either mean they use the same type of fuel, or that they
draw propellands from the same tanks. Hence question.


I think each pair of SuperDracos has its own propel lent tanks and
pressurization system.


Since the system worked for the Dracos during flight, one would want to
look at what is different when you need the Super Dracos. (Or perhaps
for the succesfull flight, the pressurized it only to the pressure
needed by Dracos, knowing SuperDracos would not be used).


I'm pretty sure they're totally independent. The pairs of SuperDracos
are fully independent from each other.


I believe this is correct. It gives the system some redundancy to have
these separate.

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.
  #26  
Old May 1st 19, 01:54 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

Jeff Findley wrote on Tue, 30 Apr 2019
14:08:51 -0400:


Also, from what I understand, there is a list of safety related issues
that NASA wanted SpaceX to take care of before flying crew on DM-2. The
other "silver lining" is that this gives SpaceX more time to take care
of those issues as well.


Would you happen to know what those are or be able to point me to a
description of them?


--
"Insisting on perfect safety is for people who don't have the balls to
live in the real world."
-- Mary Shafer, NASA Dryden
  #27  
Old May 1st 19, 01:56 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 Tue, 30 Apr 2019
15:33:58 -0400:

On 2019-04-30 14:05, Jeff Findley wrote:

You're going to get little to no actual useful information from a cell
phone video. It's way too low frame rate and the way they respond to
rapid changes in light pretty much means you can't trust the few frames
you have.


That video shows no exhaust from super dracos for a meaningful time
prior to even.


But so what? You have no idea how long the thing was just sitting
there quietly doing nothing. There was no exhaust from the
SuperDracos since the last time they were lit, after all.


And it shows a pretty big explosion with lost of debris flying.

It pretty much confirms that the Dragon 2 is a total loss. (something
which SpaceX didn't confirm at least not at the time that vode was
released).


But what does that actually tell you?


--
"Some people get lost in thought because it's such unfamiliar
territory."
--G. Behn
  #28  
Old May 1st 19, 02:19 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 Tue, 30 Apr 2019
15:39:51 -0400:

On 2019-04-30 14:10, Jeff Findley wrote:

I'm pretty sure they're totally independent. The pairs of SuperDracos
are fully independent from each other.


I believe this is correct. It gives the system some redundancy to have
these separate.


Considering current role of Super Dracos as being potentially useful
only during launch, and hopefully never used, wouldn't it make more
sense for them to share the weight of fuel with the dracos?


No, it wouldn't because now you have all the issues of adjusting for
different chamber pressures, etc.


aka: if all goes well at launch, the fuel is used by dracos during
on-orbit operations. And if Super Dracos is used during launch, you're
not going to need the fuel for dracos isn't you're not going to orbit.


Except that wasn't the way the thing was designed. I suspect SpaceX
is better at doing "the sensible thing" than you are when it comes to
their spacecraft.


I could understand separate fuel tanks in a context where the Super
Dracos would be used for every landing. (if fuel not used for launch
abort, it is then needed for normal landing and vice versa).


I suspect your 'understanding' is the least of SpaceX's concerns.


Were powered landings ruled out during Dragon 1 such that Dragon2 design
started off with powered landings already out of equation, or did they
start designing it for powered landings and then it was ruled out ?


Dragon I didn't have SuperDraco engines so it was never going to do a
propulsive landing. Propulsive landings were ruled out quite late for
Crew Dragon and the cargo variant of that craft might well still do
them someday since that doesn't raise the safety certification
concerns that eventually killed them for Crew Dragon.

They didn't "start designing it for powered landings". They also
FINISHED designing it for powered landings and built the thing that
way (with the exception of removing the landing legs, which Musk says
they could still put back with little to no difficulty). This stuff
is NOT hard to find out. You could, just occasionally, look things up
for yourself.

https://spaceflightnow.com/2017/07/1...gon-spaceship/

https://www.inverse.com/article/3440...hrust-landings

https://www.teslarati.com/spacex-cre...gency-landing/

I could go on...


--
"Ignorance is preferable to error, and he is less remote from the
truth who believes nothing than he who believes what is wrong."
-- Thomas Jefferson
  #29  
Old May 1st 19, 11:55 AM posted to sci.space.policy
Jeff Findley[_6_]
external usenet poster
 
Posts: 2,057
Default SpaceX Dragon 2 capsule destroyed in abort motor ground test

In article ,
says...

On 2019-04-30 14:10, Jeff Findley wrote:

I'm pretty sure they're totally independent. The pairs of SuperDracos
are fully independent from each other.


I believe this is correct. It gives the system some redundancy to have
these separate.



Considering current role of Super Dracos as being potentially useful
only during launch, and hopefully never used, wouldn't it make more
sense for them to share the weight of fuel with the dracos?


No. Dracos are likely much lower pressure than Super Dracos. It's much
simpler to have separate tanks in this case.

aka: if all goes well at launch, the fuel is used by dracos during
on-orbit operations. And if Super Dracos is used during launch, you're
not going to need the fuel for dracos isn't you're not going to orbit.


The intent was to use the Super Dracos for vertical landing on a nominal
mission. NASA nixed that, so we're left with them being there with no
operational use on a nominal mission. But that's the case with Boeing's
Starliner capsule as well, as far as I can tell, so Dragon 2 isn't
unique in this regard.

I could understand separate fuel tanks in a context where the Super
Dracos would be used for every landing. (if fuel not used for launch
abort, it is then needed for normal landing and vice versa).


That was the original intent, but SpaceX development is focused on
Raptor and Starship right now. Dragon 2 is done with development.
There are just a few issues to close out (admittedly this anomaly during
the Super Draco vibration / acoustic ground test is a big one to
handle).

Were powered landings ruled out during Dragon 1 such that Dragon2 design
started off with powered landings already out of equation, or did they
start designing it for powered landings and then it was ruled out ?


Powered landings were never in the plan for Dragon. It was only
designed to splashdown in the ocean under parachutes.

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.
 




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 10:27 AM.


Powered by vBulletin® Version 3.6.4
Copyright ©2000 - 2020, Jelsoft Enterprises Ltd.
Copyright 2004-2020 SpaceBanter.com.
The comments are property of their posters.