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Marc Dufour wrote:

> One will recall that ye olde apollo spaceships that sailed to the 
> moon many moons ago did sport a 1/3 bar 100% oxygen atmosphere for 
> the comfort and convenience of their valiant (but cramped) crews.
> 
> The question is how did the guys who were cooped-up in those tin cans
> for days or weeks cope with the issue of oxygen toxicity? They
> certainly could not take air breaks, for this would have reduced the
> ppO2 below what normal lungs consider useful. 

I'm no aerospace medicine specialist, but I think you might have
actually answered your own question.  If P(tot) = .33 atm, then PPO2
would have also been .33 atm.  Not enough PPO2 to cause any sizure
problems, nor produce the pulmonary irritation of chronic O2 poisoning.

Apparently using the low total pressure / high FO2 cabin approach has
some significant advantages.  Simplifies plumbing / atmosphere
maintenance and allows using low spacesuit internal pressures (for
better flexibility) without having to decompress prior to doing EVA's.
The U.S.S.R.  space program of the Apollo period did NOT use the low
pressure approach, thus the need for the airlock for the Apollo /
Solyuz mission.  I think the Space Shuttle has opted for a 1 atm.
cabin system, with a more Normox mix.

				My .02,
				Mike Chalup
				internet:   mchalup@ox*.co*

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