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 Capsule Explosion



 
 
Thread Tools Display Modes
  #21  
Old July 19th 19, 11:37 AM posted to sci.space.policy
David Spain
external usenet poster
 
Posts: 2,552
Default SpaceX Capsule Explosion

On 7/18/2019 1:44 PM, Greg (Strider) Moore wrote:
"David Spain"* wrote in message ...

Or... it could just be, "we don't trust the new folks, no matter what."


Or I could be snide and ask exactly how many refurbishment cargo flights
Boeing has made to the ISS...

If trust is measured by the amount of money awarded, then NASA answered
that question years ago...

Dave
Ads
  #22  
Old July 19th 19, 12:06 PM posted to sci.space.policy
Jeff Findley[_6_]
external usenet poster
 
Posts: 1,959
Default SpaceX Capsule Explosion

In article , says...

On 7/17/2019 7:40 PM, Jeff Findley wrote:

Doesn't matter because NASA wants only new Dragon 2 capsules for crew.
After their crew flight, they will be refurbished for commercial cargo.
Part of that refurbishment is to remove the abort system to allow for
more cargo up-mass and down-mass.

Jeff


Jeff that's a great point and I remember reading about that. Seems
stupid on NASA's part, they lose the cost savings of reusable hardware.
But hey this is the organization behind the SLS so what should I expect?

Do you have a cite for the latter part (removal of abort system for more
cargo)? I'd like to read up on that. First I've heard of it.


I couldn't find a definitive reference. But the abort system is simply
not needed for a cargo flight. It could be that the parts will still be
on the Dragon 2, but the abort system's propellant tanks and high
pressure helium tanks simply won't be filled. That would also save a
lot of mass while minimizing the modifications needed to turn a crew
Dragon 2 into a cargo Dragon 2.

I'm sure we'll find out more later. After all, for now they're still
flying the original Dragon on cargo flights.

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 July 19th 19, 02:19 PM posted to sci.space.policy
Niklas Holsti
external usenet poster
 
Posts: 95
Default SpaceX Capsule Explosion

On 19-07-19 14:06 , Jeff Findley wrote:
In article , says...

On 7/17/2019 7:40 PM, Jeff Findley wrote:

Doesn't matter because NASA wants only new Dragon 2 capsules for crew.
After their crew flight, they will be refurbished for commercial cargo.
Part of that refurbishment is to remove the abort system to allow for
more cargo up-mass and down-mass.

Jeff


Jeff that's a great point and I remember reading about that. Seems
stupid on NASA's part, they lose the cost savings of reusable hardware.
But hey this is the organization behind the SLS so what should I expect?

Do you have a cite for the latter part (removal of abort system for more
cargo)? I'd like to read up on that. First I've heard of it.


I couldn't find a definitive reference. But the abort system is simply
not needed for a cargo flight. It could be that the parts will still be
on the Dragon 2, but the abort system's propellant tanks and high
pressure helium tanks simply won't be filled. That would also save a
lot of mass while minimizing the modifications needed to turn a crew
Dragon 2 into a cargo Dragon 2.


They might even use propulsive landing for cargo flights.

--
Niklas Holsti
Tidorum Ltd
niklas holsti tidorum fi
. @ .
  #24  
Old July 19th 19, 04:13 PM posted to sci.space.policy
David Spain
external usenet poster
 
Posts: 2,552
Default SpaceX Capsule Explosion

On 7/19/2019 9:19 AM, Niklas Holsti wrote:

They might even use propulsive landing for cargo flights.


If that was the plan before replacing the check valve(s) with burst
disks, I wonder if that remains the plan?

If so it would imply that they (SpaceX) intended to fly all the way down
with pressurized engines all along anyway, so its no big deal either
way. Otherwise it would require some re-thinking.

Dave
  #25  
Old July 19th 19, 05:01 PM posted to sci.space.policy
Niklas Holsti
external usenet poster
 
Posts: 95
Default SpaceX Capsule Explosion

On 19-07-19 18:13 , David Spain wrote:
On 7/19/2019 9:19 AM, Niklas Holsti wrote:

They might even use propulsive landing for cargo flights.


I forgot about the landing legs that are needed for that. They may have
been removed from the Dragon2 design and might be hard to refit.

If that was the plan before replacing the check valve(s) with burst
disks, I wonder if that remains the plan?

If so it would imply that they (SpaceX) intended to fly all the way down
with pressurized engines all along anyway,


AIUI, there is an actuated valve at the He tank, before the check
valves, which would not be opened until just before the SuperDracos are
fired. So the engines would not be pressurized until needed.

--
Niklas Holsti
Tidorum Ltd
niklas holsti tidorum fi
. @ .
  #26  
Old July 19th 19, 05:05 PM posted to sci.space.policy
David Spain
external usenet poster
 
Posts: 2,552
Default SpaceX Capsule Explosion

On 7/19/2019 11:34 AM, JF Mezei wrote:

As the Dragon spashes down, are those tanks stil pressurized, or is
there a means to close Helim tank, and then burn engines till there is
no more pressure just before deploying parachutes?


I have no hard data on the Dracos or Super Dracos so it is difficult for
me to answer your questions. I can speculate on this last question. You
presume the only method to relieve the pressure is through combustion,
but there may also exist a pressure relief valve that vents off the
helium without need to run the engines. Without hard data this is just a
WAG but not a SWAG.

Dave
  #27  
Old July 19th 19, 05:22 PM posted to sci.space.policy
David Spain
external usenet poster
 
Posts: 2,552
Default SpaceX Capsule Explosion

On 7/19/2019 12:01 PM, Niklas Holsti wrote:
On 19-07-19 18:13 , David Spain wrote:
On 7/19/2019 9:19 AM, Niklas Holsti wrote:

They might even use propulsive landing for cargo flights.


I forgot about the landing legs that are needed for that. They may have
been removed from the Dragon2 design and might be hard to refit.

Yes that is correct they have been removed from the architecture. I had
missed that point as well. Truth is, AFAIK the original design called to
the landing legs to extrude from the heat shield. NASA was definitely
not big on this idea. And to the best of my knowledge, other than the V2
mock-up this was never implemented.

When first shown I was surprised they planned to do it that way rather
than just follow the method they adopted on F9, and just have them swing
down from the body of the capsule.

I suppose they could still go for propulsive landing over water. At sea
and then move to a large fresh water tank on dry ground? Or if
up-welling steam is a problem maybe a high boiling point oil?

If that was the plan before replacing the check valve(s) with burst
disks, I wonder if that remains the plan?

If so it would imply that they (SpaceX) intended to fly all the way down
with pressurized engines all along anyway,


AIUI, there is an actuated valve at the He tank, before the check
valves, which would not be opened until just before the SuperDracos are
fired. So the engines would not be pressurized until needed.


Yeah but once needed always on is the point. After a landing I'd think
you'd want to vent that helium pressure off. But maybe you shouldn't
until the bi-propellant is drained? And if back flow is a problem with a
check valve you can imagine the issues you might run into if you kill
helium pressure with a now a burst burst disk.

Not enough data...

Dave
  #28  
Old July 20th 19, 01:31 PM posted to sci.space.policy
David Spain
external usenet poster
 
Posts: 2,552
Default SpaceX Capsule Explosion

On 7/19/2019 2:43 PM, JF Mezei wrote:
On 2019-07-19 12:05, David Spain wrote:

presume the only method to relieve the pressure is through combustion,
but there may also exist a pressure relief valve that vents off the
helium without need to run the engines. Without hard data this is just a
WAG but not a SWAG.



You can vent off the Helium between the Helium tank and the
Fuel/oxydizer tanks. But the pressure inside the later tanks can't be
vented otherwise you are venting uncombusted NTO and MMH which may
combust if they meet after having been ventet and remain highly toxic if
they don't meeet to combust.


You close the Helium pressurization valve, and de-press through another
valve and coupling perhaps one at the top of the helium tank.

The NTO and MMH would be drained via separate plumbing connections,
which already must exist to fuel it anyway.

Then you purge the system with helium to remove the trace elements of
NTO and MMH from the pressurization lines. Yeah if you do it together
you stand back, otherwise you do them singly with lots of venting to
allow it do disperse.

I can make up a lot of stuff too w/o data it's a WAG (Wild Ass Guess)
but not a SWAG (Silly Wild Ass Guess).

Dave

  #30  
Old July 20th 19, 01:47 PM posted to sci.space.policy
Jeff Findley[_6_]
external usenet poster
 
Posts: 1,959
Default SpaceX Capsule Explosion

In article , says...

On 7/19/2019 9:19 AM, Niklas Holsti wrote:

They might even use propulsive landing for cargo flights.


If that was the plan before replacing the check valve(s) with burst
disks, I wonder if that remains the plan?


It wasn't. NASA has prohibited SpaceX from performing Dragon 2
propulsive landing testing on returning ISS cargo flights. NASA does
not want the added risk for any of its returning cargo. This is why
SpaceX dropped development of propulsive landing for Dragon 2. This
decision happened quite some time ago.

If so it would imply that they (SpaceX) intended to fly all the way down
with pressurized engines all along anyway, so its no big deal either
way. Otherwise it would require some re-thinking.


As with an abort, during a propulsive landing the tanks would only have
been pressurized as part of the Super Draco engine firing sequence, so
they would have been pressurized a fraction of a second before firing
the Super Draco engines. Also, if it performed an abort, it would
necessarily use parachutes for the splashdown. There was never enough
propellant to perform an abort *and* a propulsive landing. It was
always either/or.

The genius of propulsive landing was that on a nominal mission (i.e. no
launch abort), you could use the abort system's engines and propellant
to perform the propulsive landing. For comparison, Starliner's abort
system is in its service module, so it will always be destroyed after a
nominal mission, because the service module burns up on reentry.

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 Dragon 2 capsule destroyed in abort motor ground test Jeff Findley[_6_] Policy 59 July 12th 19 08:30 AM
Latest candidate for SpaceX pad explosion Fred J. McCall[_3_] Policy 50 October 28th 16 06:54 AM
SpaceX Falcon 9 ? Possible Explosion Jeff Findley[_2_] Policy 22 October 9th 13 09:54 AM
SpaceX capsule has 'new car' smell, astronauts say [email protected] Policy 5 June 2nd 12 08:09 PM
Space Station's Robotic Arm Successfully Captures SpaceX Capsule Sam Wormley[_2_] Amateur Astronomy 0 May 25th 12 03:36 PM


All times are GMT +1. The time now is 03:26 PM.


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.