system
Given the following post, respond as if you're commenting on Reddit:
human
How does the international space station get fresh air?

Forgive me if this is a stupid question but I was wondering what process they use to get oxygen up there.
gpt
The production of oxygen aboard ISS uses 2 main processes:

- Electrolysis. This process involves running a direct electric current through water to separate it into oxygen and hydrogen. This produces the oxygen needed to breathe, but has hydrogen as a byproduct.

- Sabatier process. This uses a combination of carbondioxide and hydrogen to produce waterr and methane.

So the source of the oxygen is the electrolysis process and the Sabatier process "recycles" the carbondioxide that we produce while breathing and uses the hydrogen from the electrolysis to produce water that can then be used in the electrolysis again. The methane produced in the Sabatier process as well as any excess hydrogen is vented.

Since this is not a perfect closed loop, new water has to be brought up from Earth in supply missions to keep the systems running. So that is ultimately where the fresh oxygen comes from: Water sent up to ISS from Earth.

As a backup, there are also cans of pressurized oxygen as well as chemical oxygen generators using solid fuel oxygen available.