On 19-07-21 16:48 , Jeff Findley wrote:
In article ,
says...

On 2019-07-20 10:16, Jeff Findley wrote:

Scott Manley's video showed springs pushing valve down (to illustrate
the backflow prevention). Is this how the real valve would function?

Yes.

systems than I do) speculate is that (relatively warm) gaseous NTO snuck
past the check valve and then re-condensed to liquid in the (relatively
cold) helium plumbing.


Shoudln't a check valve prevent passange in wrong direction on either
gas or liquid? It's not like there is a floater that rises up to close
valve is liquid rises up, is it?

You really can't rely on a check valve for this. That's why designs
also include (usually redundant) isolation valves. No, I don't know why
NASA "has always done it this way" if an isolation valve would have been
better.

With apologies to those who also follow the "arocket" list, I note that
on that list, Lars Osborne recently pointed out that the SpaceX
statement actually says "a leaking component" but does _not_ say that it
was the check valve that leaked.

Osborne continues as follows: "My intuition is that they did have
multi-use isolation valves, and those were what leaked during the
propellant loading, and of course the MON vapors would migrate through
the check valve."

While the fix involves replacing the check valves with burst disks, this
still does not strictly imply that the unexpected leak occurred in a
check valve.

--
Niklas Holsti
Tidorum Ltd
niklas holsti tidorum fi
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