Environmental Control & Life Support

Sensors continuously track the cabin's oxygen, carbon dioxide, pressure, and trace contaminants, so that the life-support system can respond and the crew is warned of any hazardous change in their air.

The carbon dioxide a crew exhales must be continuously removed from the cabin air. Systems use regenerable sorbents or amine beds to scrub it out, and increasingly to recover its oxygen rather than venting it overboard.

Systems that produce breathable oxygen in a closed cabin, typically by splitting recovered water into oxygen and hydrogen through electrolysis, so a crew is not wholly dependent on tanks brought from Earth.

Life support must hold the cabin at a comfortable, safe temperature and humidity, removing the heat and moisture that crew and equipment add and preventing condensation that could damage systems or grow microbes.

Systems for collecting and processing human waste and trash in weightlessness — from the spacecraft toilet to the handling of solid waste — protecting crew health and, increasingly, recovering water and resources.

On the ISS, most of the crew's water is recycled — reclaimed from humidity, hygiene water, and urine and purified back to drinking quality. Closing the water loop is essential to missions too far to resupply.