A Brief History of the Pressure Suit
Environmental influences have fashioned man in such a manner that he can only survive within certain limits of pressure and temperature. When man flies at altitudes above 10,000 feet, he is forced by environmental conditions to wear protective equipment in order to maintain normal physiological processes. In essence, he must take his own environment with him in the form of a pressurized cabin supplemented by equipment such as oxygen mask and pressure suits.
The effects of atmospheric pressure on the human body determines what type of protective equipment is required. At sea level the atmosphere exerts a pressure of 14.7 psi., this is what most people are accustomed to. As you go higher into the atmosphere, such as driving in the mountains or flying on a commercial airliner, gases start to expand due to the lower atmospheric pressure. This is what causes your ears to have that popping sensation. At altitudes higher than 10,000 feet people unaccustomed to the reduced atmospheric pressure may become short of breath or experience dizziness. At altitudes above 20,000 feet supplemental oxygen is required to support life. At 34,000 feet, 100% oxygen is necessary to equal the partial pressure of oxygen in sea level air. Above 40,000 feet, 100% oxygen must be under positive pressure to maintain the equivalent altitude of 10,000 feet.
At altitudes above 50,000 man requires a pressurized suit to be safe in this near space environment. At 55,000 feet, atmospheric pressure is so low that water vapor in the body appears to boil causing the skin to inflate like a balloon. At 63,000 feet blood at normal body temperature (98 F) appears to boil. Just as your ears pop while traveling through the mountains or flying on an airplane, reduced atmospheric pressure at these high altitudes allow the gases in your body to expand to the point where they appear to boil off. At altitudes above 65,000 feet atmospheric pressure approaches that of space, that is the pressurization factors for protective equipment to be used at 65,000 feet are essentially the same as would be required for survival in a vacuum.
Ever since it was discovered that life could be supported in a vacuum by pure oxygen delivered to the body at a pressure slightly less than 3 psi, many interesting attempts have been made to translate this simple physiological fact into a practical form. The first attempts at pressure suit construction resulted in what was, in effect, a mobile form-fitting pressurized cabin which was capable of surrounding the enclosed subject with an envelope of pressurized oxygen. This all-enclosing principle, evolved as a full pressure suit. The full pressure concept is theoretically the ideal system of providing a livable atmosphere in an otherwise lethal environment.
The early partial pressure suit, designed to be worn under ordinary flying clothing, consisted of a close-fitting elastic nylon and cotton garment which covered the entire body from the ankles to the neck and wrists. A system of inflatable tubes called capstans are attached to the basic garment, when inflated the capstans through the action of crossing tapes, tighten the fabric of the suit on the body. The objective was to supply the amount of counter pressure which will just balance the breathing pressure necessary to prevent hypoxia at a given altitude. Various models of this suit were worn by pilots of fighter aircraft, bombers and high altitude flights of research aircraft beginning with the X-1.
Early designs worked well but had areas that needed work, specifically heat build up, weight and bulk, and lack of mobility while pressurized. This led to the development of what would become the modern day full pressure suit. The modern pressure suit consist of a gas bladder that maintains a pressure of approximately 3 psi on the body when inflated, it has built in ventilation systems and survival components.. The flying ensemble includes a full pressure helmet as well, giving the wearer a complete mobile pressurized environment. Variations of the modern full pressure suit exist for flying at high altitudes to walking in space.