David.Smith@CMU-CS-A (11/17/82)
From: David.Smith at CMU-CS-A (C410DS30)
1. Why 100% oxygen? The astronauts need a certain partial-pressure of
oxygen, but they do not need sea-level pressure. If the suit were
further inflated with nitrogen, then it would balloon much worse
than it does, and the astronaut could move only with difficulty, if
at all.
2. A small amount of CO2 to avoid hyperventilation? I think it would
be the other way around. The urge to breathe is caused by the
presence of CO2, not the lack of oxygen. If the oxygen supply is
perfectly normal, while amount of CO2 is abnormally high, then the
person would hyperventilate. (Maybe a small amount of CO2 to
avoid hypoventilation, but that could be supplied by the astronaut
himself, given a proper flow rate.)
3. Sea level pressure? No. It sticks in my mind that Apollo used
5 psi of pure oxygen, and that the suits used lower pressure than
that. I don't know the pressure used in the Shuttle suit, but
I am confident that it would not be over 5 psi.
4. Why 2-piece suits? So you can mix & match upper and lower body
sizes, and not have to tailor a new suit to each astronaut.
5. Why use a pressure suit at all? Well, for one thing, at low
enough pressure (above 60,000 feet), the blood will boil at
body temperature. I don't know that the example of the feet
demonstrates anything. The soles of the feet experience overpressure.
-- David Smith @ cmu-cs-a