Typically for loading and unloading propellant you use the same connection
on the bottom of the tank, just reversing direction.
You could maybe oscillate flow in and out one fitting while stirring the
tank, but it would be more complex than necessary.
On Tuesday, November 8, 2016, Jake Anderson <dmarc-noreply@xxxxxxxxxxxxx>
wrote:
On 08/11/16 15:59, Henry Spencer wrote:
On Tue, 8 Nov 2016, Jake Anderson wrote:need to actually work?
Do you actually need to move the lox? if you are trying to keep it cold
could you perhaps do that through the skin of the vehicle/tank? IE put a
panel in good thermal contact with the tank (at the top of the fill level
perhaps to help with stratification etc) with a LN2 loop running through
it...
That's just a heat exchanger by another name, alas. Building a good heat
exchanger that will break in the middle on command is likely to be hard;
the panel won't be a perfect fit to the skin, and any gap not only will
ruin its effectiveness as a heat exchanger, but also will fill in with ice
pretty quickly, unless you add a helium purge to keep air out...
It's not easy to make that sort of thing work well. The original Centaur
jettisoned the insulation on its LH2 tank at startup, but that led to the
same problems with icing and purging, and fixes added so much mass that
Centaur performance actually *increased* when they switched to foam
permanently bonded to the tank.
The simpler way to put in a good heat exchanger is to make it a permanent
part of the tank. But good heat exchangers tend to be heavy.
Moving the LOX actually is the easy way, because it lets you put all the
heavy equipment on the ground side of the disconnects.
Henry
It would be difficult to make one that works "well" but how well would it
If you aren't constrained by weight or size on the ground side an
inefficient heat transfer might be enough, or at least enough to extend the
time during which you can keep the lox below TemperatureX
If NASA aren't happy about lox loading with crew aboard would they be ok
with pumping it in and out instead? I guess it'd be a steady state you
could achieve in advance of crew loading rather than dumping lots of cold
stuff in.
I suppose all that's needed for the circulate cold lox option would be one
extra valve and a coupling off the main lox line so it'd be simpler in that
regard. Actually they can already defuel the rocket so they must already
have that plumbing in place and would just need GSE modifications to allow
it?
Either way one would presume there might be operational benefits to being
able to have an extended launch hold with the vehicle fuelled, as I recall
they missed a few launch windows due to things like that.
