[net.space] Shuttle atmosphere - why just N2, O2?

msb@lsuc.UUCP (Mark Brader) (08/13/85)

Jerry Hollombe quotes  The Space Shuttle Operator's Manual:

> "An atmosphere like the earth's is  maintained  in  the  crew  compartment.
> Atmospheric  pressure  is  14.7  psi  ...  the  same  as standard sea-level
> conditions.  The atmosphere consists of 79% nitorgen and 21% oxygen,  again
> very  close  to what you left on earth.

So my question is why they use THIS atmosphere rather than plain air
(78% nitrogen, 21% oxygen, 1% argon).  I would imagine the oxygen supply
is in a different reservoir so that pure oxygen can be used if necessary,
but even so, the other reservoir could contain air-minus-oxygen rather
than straight nitrogen, and I would think that that is cheaper to produce.

Mark Brader