How do astronauts breathe inside a spacecraft?
Quick Answer
Spacecraft recycle air and add oxygen from tanks or onboard systems, while removing carbon dioxide with scrubbers. The International Space Station’s cabin pressure is kept near Earth-like levels, around 14.7 psi.
The Full Story
Inside crewed spacecraft, life-support systems keep the air breathable by supplying oxygen and removing carbon dioxide. Early missions relied mainly on stored oxygen, but modern spacecraft can also generate oxygen from water or use oxygen candles and tanks as backup. Carbon dioxide is removed by chemical scrubbers, such as lithium hydroxide in some systems or regenerable filters on the ISS. Cabin pressure is usually kept close to Earth conditions so astronauts can breathe normally, though some spacecraft use slightly different mixes for safety and efficiency. These systems are part of the Environmental Control and Life Support System, or ECLSS.
Key Facts
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