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Old May 1st 04, 08:34 AM
Doug...
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In article , says...
In article ,
Bill wrote:
Were all the Apollo flights made in a one-gas (pure oxygen)
environment? It seems that the thin skin of the LM made it necessary
to limit the cabin pressure to 3.5 psi and required a one-gas system.


That, plus the need to do spacewalks without lengthy prebreathing, plus
the much greater complexity of two-gas life-support systems.

Post-fire, Apollo used 60% oxygen 40% nitrogen as the *cabin* atmosphere
on the pad, but the crew always breathed pure oxygen, and the cabin
shifted to pure oxygen during ascent.


Pre-Fire, of course, the cabin was pressurized to roughly 17 psia of
pure oxygen. They also overpressurized the cabin at times during post-
Fire operations, but as Henry says, the air was 40% nitrogen.

The cabin pressure was maintained at roughly 5 psia in both the LM and
the CM. This was a little higher than the natural partial pressure of
oxygen in sea-level air. During EVAs (any time they were in hard
suits), the suit pressure was maintained at about 3.5 psia. You could
put more air pressure in the suits, but the higher the pressure the
"harder" the suit became... it would become very much harder to do
simple things like raise your arm to eye level in a suit pressurized to,
say 4.5 psia than in a suit at 3.5 psia. (Eric Jones discusses this in
several of the Apollo Lunar Surface Journals, and most of the Apollo
moonwalkers confirmed that they had a harder time working in such
"harder" suits.)

Doug

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