[AR] Re: tank frost (was Re: LH2.... Density)
- From: Henry Spencer <hspencer@xxxxxxxxxxxxx>
- To: Arocket List <arocket@xxxxxxxxxxxxx>
- Date: Sat, 15 Jun 2019 22:31:05 -0400 (EDT)
On Sat, 15 Jun 2019, Jonathan Goff wrote:
I wonder if you could do a CO2 purge instead of helium--get something
that will deliberately solidify at those temperatures that you could
fill the air with in higher quantities than just humidity.
Maybe; it would depend a lot on the physical properties of the solid.
(One cannot assume that everything is sort of like water ice -- there is
wide variation in properties. Even solid oxygen and solid nitrogen differ
quite significantly.) Might be possible to find something suitable.
IIIRC didn't the common bulkheads on one of the past LOX/LH2 stages use
a honeycomb filled with CO2 in the bulkhead with the intent of having
the CO2 freeze to one side of the bulkhead creating vacuum in the
honeycomb cutting down on heat flux?
Centaur's bulkhead used a thin layer of fiberglass insulation filled with
GN2 -- when the gas is trapped in the sealed bulkhead, even nitrogen will
freeze out to high-vacuum levels when there's LH2 on one surface. They
did a thorough initial GN2 purge to make sure there wasn't any helium in
there, and it turned out that they had to really sweat weld quality on the
LH2 side, because even a minute hydrogen leak into the bulkhead is enough
to spoil the vacuum.
I have a vague recollection that the LH2 stages of the Saturns used the
same technique with honeycomb, but a quick look doesn't find confirmation
(or anything about their choice of fill gas).
Henry
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