Space stations such as the International Space Station (ISS) depend on a reliable and continuous supply of oxygen to sustain astronauts during missions. The primary technique used to generate oxygen aboard these stations is the electrolysis of water. This process involves applying electricity to split water molecules into oxygen and hydrogen gas. The oxygen produced is then released into the station’s cabin atmosphere for breathing.

The hydrogen byproduct is managed in one of two ways: it can either be vented outside the station or combined with carbon dioxide to form water again. This newly formed water can then be recycled back into the electrolysis system, creating a closed-loop cycle that maximizes resource efficiency.

Managing the station’s air quality also requires the removal of carbon dioxide, as elevated concentrations can be harmful to crew members. Systems onboard continuously scrub carbon dioxide to maintain a safe and breathable environment.

In addition to electrolysis, space stations carry backup oxygen supplies to ensure crew safety during emergencies. These include high-pressure oxygen tanks and chemical oxygen generators. The latter produce oxygen through controlled chemical reactions and serve as an essential contingency in case the primary systems fail.

Water recycling is another critical component of sustaining human life in space. Stations reclaim water from astronauts’ urine, sweat, and cabin humidity, purifying it to provide adequate drinking water and feed the oxygen-generation equipment. This closed-loop water management is vital for long-duration missions, where resupply from Earth is limited.