As man ventures out of his Earth's environment it is obvious that he must carry his
"environment" with him. As his craft climbs away from Earth, the atmospheric pressure
gradually diminishes until it disappears entirely. Beyond 40,000 feet, the limit for
unpressurized flight, lungs no longer absorb sufficient oxygen to replenish the bloodstream;
beyond 460,000 feet the atmosphere no longer provides protection against
micrometeoroids. Were the pilot's pressure suit to be punctured by micrometeoroids, death
would rapidly follow; therefore, several layers of plastic protect the pressure-retaining layer of
the suit. Pressure-suit development was an inevitable outgrowth