A pressure suit is a protective suit worn by high-altitude pilots who may fly at altitudes where the air pressure is too low for an unprotected person to survive. Pressure suits have been in development since the early 1930s because during this period flight in unpressurized aircraft began reaching heights where the air became too thin to breath efficiently.
Elevations ranging from sea level to around 10,000 ft have sufficient oxygen for the human body to breathe easily. Pike’s Peak, Colorado is 14,000 ft high. At that elevation it is difficult for a young, healthy, non-smoker to catch their breath, but decompression sickness is rare. From 12,000 ft to about 50,000 ft, the higher a human goes the higher the risk of high altitude sickness or complications of gases trapped within body tissue. An oxygen rich breathing mixture is required above about 34,000 ft, which is slightly below the service ceiling of most unpressurized WWII strategic bombers. Above 40,000 ft oxygen must be administered under positive pressure.
Above the Armstrong limit, the altitudes at which modern fighter aircraft operate or 63,000 ft, fluids in the throat and lungs will boil away. Generally, pressurized 100% oxygen is used to maintain an equivalent altitude of 10,000 ft. Partial pressure suits that only pressurize certain parts of the body provide protection up to a certain altitude. Full pressure suits that pressurize the entire body have no altitude limit.
Altitudes near the fringe of space require additional protection from space radiation, also known as cosmic rays that consist of particles from the sun, protons, helium, x-rays, gamma rays and other harmful elements from distant sources. An additional outer layer of the suit reflects these harmful forms of energy. On display is a very early version of such a suit. Crews of very early near space vehicles such as the X-15, U-2 and SR-71 helped develop this envelope of safety into what Astronauts wear today when performing extra vehicular activities (space walks).