View Single Post
  #18  
Old July 18th 19, 07:43 PM posted to sci.space.policy
Fred J. McCall[_3_]
external usenet poster
 
Posts: 10,018
Default SpaceX Capsule Explosion

David Spain wrote on Wed, 17 Jul 2019 20:51:19
-0400:

On 7/17/2019 7:43 PM, Jeff Findley wrote:

See above. They burst when the hypergolic system for the Super Dracos
is pressurized, which is only when an abort is initiated.


I don't see how that answers my question. I must presume there is
another (helium) valve upstream of the burst disk that holds back the
helium pressure until an abort. It's the helium gas that's doing the
pressurization correct? So I would assume that's implied in Fred's OP.


It can all be one piece, hence 'burst valve'. The valve opens, which
allows pressurized helium to hit the burst disk. When pressure at the
disk is sufficiently high, the disk bursts. This prevents backflow
into the helium system.


Is helium used for pressurizing both bi-propellants? I would assume so.
But always welcome facts if at hand. I can Google it too if anyone
doesn't already know.


From the descriptions I've read helium is used to pressurize both
tanks and shares piping. Remember, the problem here was a cup of
oxidizer getting over to the propellant side of the helium system and
contacting a titanium valve over there under pressure.


--
"Insisting on perfect safety is for people who don't have the balls to
live in the real world."
-- Mary Shafer, NASA Dryden