Thank you. So the Delta I/II/III used nitrogen? I guess not all Western
rockets (or all "dino-space") use/used helium for LOX pressurization. Now
I'm curious about Falcon 9 and Ariane V. I can see where nitrogen could be
a problem with the densified, chilled LOX in the latest Falcon 9s.
On Fri, Apr 22, 2016 at 7:54 PM, Henry Spencer <hspencer@xxxxxxxxxxxxx>
wrote:
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
