Keeping Your Cool
It is not sufficient for the health and well-being of an astronaut just to be protected from the hazards of the environment in which he or she is trying to work. It is also necessary to consider the conditions that are created by the suit itself. One of the most important of these conditions is temperature. Suit insulation technologies protect the astronaut from extreme high and low temperatures of the space environment. However, the same insulation technology also works to keep heat released by the astronauts body inside the suit. To get an idea of what this is like, imagine walking around in summer wearing a plastic bag. For this reason, an active cooling system is employed.
In Space Shuttle Extravehicular Mobility Units or EMUs, the cooling system consists of a network of small diameter water circulation tubes that are held close to the body by a Spandex® body suit. Heat released by the astronauts body movements is transferred to the water where it is carried to a refrigeration unit in the suit's backpack. The water runs across a porous metal plate that is exposed to the vacuum of outer space on the other side. Small amounts of water pass through the pores where it freezes on the outside of the plate. As additional heated water runs across the plate, the heat is absorbed by the aluminum and is conducted to the exposed side. There the ice begins to sublimate, or turn directly into water vapor and disperses in space. Sublimation is a cooling process. Additional water passes through the pores, and freezes as before. Consequently, the water flowing across the plate has been cooled again and is used to recirculate through the suit to absorb more heat.
Supplementing the EMU cooling system is an air circulation system that draws perspiration-laden air from the suit into a water separator. The water is added to the cooling water reservoir while the drier air is returned to the suit. Both the cooling system and the air- circulation system work together to contribute to a comfortable internal working environment. The wearer of the suit controls the operating rates of the system through controls on the Display and Control Module mounted on the EMU chest.
To investigate and experience the way the water cooling system in the Space Shuttle EMU functions.
Water Cooling-Part One
This demonstration shows the principle behind the operation of the Space
Shuttle EMU liquid cooling garment. Instead of an internal heat source
(the suit wearer), the heat is provided by a strong electric light bulb
or flood lamp.
Step 3. Place the two cans on a table top. Direct the light from a strong light bulb or flood light to fall equally fall on the two cans. The light should be no more than about 25 centimeters away from the cans. Fill a bucket with ice water and elevate it above the two cans. Place the catch bucket below the two cans.
Step 4. Turn on the light. Observe and record the temperatures on the two thermometers. After two minutes, again observe and record the temperatures.
Step 5. Place the upper end of the aquarium tubing into the ice water and suck on the other end of the tube to start a siphon flowing. Let the water pour into the catch bucket.
Step 6. Observe and record the temperature of the two cans at regular intervals for ten minutes.
Water Cooling -Part Two
This demonstration permits students to experience the water cooling technology used in the Space Shuttle EMU.
Materials and Tools Checklist