Test Subject page 2 of 3
This open box structure was placed inside the 20-foot diameter vertical cylindrical main vacuum chamber. Tubes were formed in the walls of the box so that liquid Nitrogen could flow through at a temperature of about –300 degrees Fahrenheit. The floor was heated by electrical heaters because the boots of the space suit were not qualified for direct contact with cold surfaces. A thermocouple to control the electrical heaters was attached to the top surface of the floor. The thermocouple sensor was attached to the floor with tape. The aluminum framework inside the box helped prevent contact with the walls. A vision chart was attached in the left front corner of the box. Fluorescent shop lights specially modified for use at vacuum provided light inside the box. The vacuum attainable in the main vacuum chamber is roughly 1/1000 normal atmospheric pressure. This is approximately the pressure at an elevation of 240,000 feet above sea level.
This close scan of the floor area shows the thermocouple sensors attached to the floor with tape.
This view shows a full view of the suit. The yellow rubber galoshes are not part of the suit, but are used to protect the flight boots from scuffing on the facility floor. Since the suit operates at such a low pressure when at vacuum, all nitrogen must be removed from the suit test subject’s body just prior to the test. This is the same thing as a staged return to the surface when diving in deep water. The suit is flushed with 100% oxygen gas and of course a few breaths remove most of the nitrogen from the lungs. However, at that time 3 hours was considered to be the time necessary for nitrogen in the body tissues to be flushed out by the blood circulation to the lungs. Again this is unnecessarily detailed, but that’s why I had to sit there for three hours before the pressure in the chamber could be reduced to vacuum. The 'Lock Observor' stood by me to provide rescue in the event of problems. The Lock Observor waited in the 'manlock' during the time the chamber was at vacuum. His responsibility was to provide direct observation of the progress of the test and to report problems. The manlock pressure was 1/2 atmosphere so the Lock Observor had quick access to the chamber during an emergency repressurization.
   The aluminum coated Mylar-covered lines draped over the metal rail provide a flow of oxygen to the suit and exhaust from the suit through a pressure regulator that maintains the suit at the correct pressure during chamber depressurization, operation at vacuum, and repressurization to normal pressure. I think our set-up approximated a spacecraft life-support system which recirculates oxygen through a carbon dioxide removal chemical and a cooling heat exchanger which removes the excess humidity like an air conditioner does and cools the oxygen before it returns to the suit. There might have been a slight loss of oxygen through the pressure regulator and suit leaks. The lost oxygen was made up from a facility oxygen supply to the system.
  This is a closeup photo to show detail of temperature sensing devices. Just visible in the lower right corner is the suit pressure gauge. Its range is 5 psi to 2.5 psi. When the suit is operating at vacuum (or zero absolute pressure) the pressure inside the suit was about 3.75 psi higher than vacuum. Since vacuum pressure is effectively 0 psia the suit pressure is 3.75 psia. Automobile tires are normally inflated to about 35 psi above normal atmospheric pressure (14.7 psia) so the air inside a tire is about 50 psia. The suit pressure (between the inside and outside) has to be low for flexibility. It would be nice to have a suit that can be operated at 14.7 psi (inside to outside), then when operating at vacuum, the pressure inside would be 14.7 psia or the same as normal atmospheric pressure.
But since that higher pressure would make the suit stiff and unmovable, it operates at the much lower pressure of 3.75 psia and therefore 100% oxygen must be used in the suit because of the physiology of the lungs and the transfer of oxygen to the blood stream as a function of the partial pressure of oxygen. This is too complex to explain here, but the result is that there is a greater chance of fire, “bends”, and loss of consciousness because of low pressure than there would be operating at 14.7 psia. (The current Shuttle EVA suit operates at about 4.3 psia/psi because joints and gloves have improved flexibility.) If you would like a detailed answer to some specific question about this, let me know.
   A bundle of wires connects the instruments, communication, and bio-medical sensing equipment in the suit to the facility data recording and communication systems outside the chamber.
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PAGE ONE - NASA photos showing me in a Gemini space suit during preparations for a thermal-vacuum test of the helmet visor prior to GTS-4. The test, test objective and temperature instruments on the helmet are described.

PAGE TWO - NASA photos of the thermal compartment that sat inside a large vacuum chamber. A full view of the suit with a description of various suit components. A close-up view of the upper suit and helmet showing the thermal sensors on my nose and on the helmet.

PAGE THREE - A scan of the NASA photo of me that appeared in the April 19, 1965 issue of Missiles and Rockets. My photo of the closed-circuit television view of Ed White during his vacuum chamber training for GTS-4. The test results are summarized and I describe what being in a spacesuit at thermal-vacuum conditions was like for me.
LINKS

SMEAT - The Skylab Medical Experiments Altitude Test
My photos of the 56-day vacuum test with Bob Crippen, Karol Bobko, and Dr. Bill Thornton. Features Jessica Savitch on the news team that reported the chamber entry and an anecdote about presidential candidate George McGovern, who visited during the test.

First US Woman EVA - My experience with Kathy Sullivan's training for this major event in space exploration history.

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