A space station must maintain an atmosphere similar to that on Earth in order for it to be habitable. In the ISS, oxygen is made by electrolysis. A generator splits water into oxygen and hydrogen. Carbon dioxide is collected by special materials and released into outer space. Water is recycled for maximum efficiency. It is collected from various sources including urine, sinks and showers, and cleaned for reuse. The ISS is heated by all the electronic equipment on board.
The air and water on the Space Station all originally came from Earth. Astronauts and cosmonauts transport these vital supplies to the Space Station when they travel there on Soyuz capsules (a type of spacecraft). Astronauts and cosmonauts also receive supplies from uncrewed spaceships, such as the Russian Progress and American Dragon. Uncrewed means with no people on board.
But fresh supplies from Earth aren’t enough to sustain the Space Station. That means if you’re onboard the Space Station you are really, really into recycling. The Space Station’s water recycling system produces pure drinking water from waste water, sweat and even urine. In the words of astronaut Douglas Wheelock, “Yesterday’s coffee is tomorrow’s coffee.”
Water, which is made of oxygen and hydrogen atoms bonded together, is also used to maintain oxygen supply on the International Space Station. Using a process called electrolysis, which involves running electricity through water, astronauts and cosmonauts are able to split the oxygen from the hydrogen.
Electricity is one thing on the Space Station that doesn’t come from Earth, as the Space Station’s vast solar panels convert sunlight into power. But what’s done with the hydrogen that’s left over? Using some chemistry and smart thinking, they’re actually able to turn it back into water! The hydrogen is combined with carbon dioxide (that the astronauts and cosmonauts breathe out) to produce water and methane. So now there’s some more water to drink, while the methane is simply waste that is blown out into space through special vents.
So if you get a chance to see the Space Station tonight, you can marvel at many things. Marvel at a spaceship travelling more than seven kilometres every second. Marvel that you can see where people live 400 kilometres above the Earth. And marvel at recycling that keeps people alive in the harsh environment of space.