| Atmosphere Control |
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Breathing the proper mixture of air is also of utmost importance aboard a spacecraft, where any mishap may put everyone's lives in jeopardy. A spacecraft must have an atmosphere similar to that of Earth. Chemical gases, which can also be produced by humans, must be carefully filtered from the air. Filtered substances are often recycled.
Here on earth, our atmosphere is composed of 78% nitrogen, 21% oxygen, and 1% other gases. A low level of oxygen in the air can cause a person to feel extremely tired, or even faint. It is therefore crucial to maintain the proper atmosphere in a spacecraft. Liquid oxygen and liquid nitrogen are carried on board in pressurized tanks, and the cabin pressurization system combines the gases as necessary at normal atmospheric pressure.
The carbon dioxide, ammonia, urea, and other chemicals that are produced from exhaling, sweating, or urinating must be removed. Chemical leaks, spills, and outgassing (gas lost from a solid) must be filtered from the air as well. Filters and charcoal canisters remove these substances from the air supply. These filtered substances are recycled as much as possible. For example, carbon dioxide can be converted to water and reused.
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