[AR] Re: pressurization (was Re: Portland State Aerospace Society)
- From: Henry Spencer <hspencer@xxxxxxxxxxxxx>
- To: Arocket List <arocket@xxxxxxxxxxxxx>
- Date: Fri, 22 Apr 2016 21:54:49 -0400 (EDT)
On Fri, 22 Apr 2016, Paul Mueller wrote:
I'm curious what problems the Atlas V had with the waffle-grid aluminum.
Did it cause a problem with pressurization? I'm assuming they also used
helium.
Yep, the Atlas family has always used helium. (Thor and Delta I/II/III,
by contrast, pressurized their tanks with nitrogen.)
The problem with the switch from the thin stainless tanks of Atlas III to
the thicker waffle-grid aluminum of Atlas V was that, between the larger
surface area and the much higher thermal conductivity, it cooled the
helium much more effectively. The result was much higher gas density, and
hence a need for higher flow rates and much more helium storage -- and so
Atlas V's pressurization system is much heavier than Atlas III's. People
had expected it to be worse than Atlas III, but nobody realized just how
*much* worse it would be. Making the design close at all turned into a
real struggle.
Henry
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