CC.CLYDE@UTEXAS-20@sri-unix (11/24/82)
From: Clyde Hoover <CC.CLYDE at UTEXAS-20>
The principal reason that U.S. spacecraft used 100% O2 at 5 psi
was that this meant the hull could be thinner and lighter, which was
important because, until the Saturn V, the boosters available to NASA
were MUCH smaller than those available to the Soviets. They had BIG
rockets for their BIG and HEAVY nukes, so the Soviets could afford to
have the heavier hulls to hold sea-level pressure.
More spacecraft weight also cut down upon its capabilities
(which matters when sending things to the Moon - less structural weight
equals more maneuvering fuel, and/or more science).
The shuttle was designed from the start to use an Earth-normal
atmosphere, which means that before going EVA it is necessary to purge
the nitrogen from the bloodstream to prevent the bends.
There is yet another reason for space suits that no one has
mentioned - radiation. The layers in the suit are designed to stop some
of the most prevelant types of particles whipping around (at least the
Apollo moon suits were), something important if you are going to be
galavanting around outside your ship for very long and want to, among
other things, have normal children (or not die of radiation poisioning).
-Clyde
-------