How Does The ISS Get Oxygen And Water?
How do astronauts make resources such as oxygen and water last until the next supply mission?
At regular intervals, supply modules are launched to the International Space Station (ISS). They bring everything that the astronauts need, including water and oxygen. However, the ISS's six inhabitants would die of oxygen deficit between two supply missions, if recycling systems did not utilize the water and oxygen aboard as efficiently as possible.
Astronaut urine is collected and sent through a system, in which it is filtered and chemically purified, so it can be reused as drinking water. And all the water vapour produced in the air of the space station is retrieved, purified, and reused. Vapour from wet towels, sweat from the gym, and moist from astronaut exhalation air also end up in a plant, in which the water vapour of the air is condensed and purified. The system makes sure that about 93 % of the water flown to the space station is reused.
Water is particularly valuable, as it is also used to produce oxygen, which the astronauts inhale. In electrolysis, water molecules are split and converted into oxygen and hydrogen. The oxygen is used in cabin air, whereas the hydrogen cannot be used, so it is lost in space.