Space stations, like the International Space Station (ISS), primarily get their oxygen through electrolysis of water.
Here's a breakdown of the process and other methods:
Electrolysis of Water
- What it is: Electrolysis involves using electricity to split water (H₂O) into its constituent elements: hydrogen (H₂) and oxygen (O₂).
- How it works on the ISS: The ISS has systems that circulate water and apply an electrical current to it. This breaks the bonds between the hydrogen and oxygen atoms. The oxygen is then released into the cabin atmosphere for the astronauts to breathe.
- Hydrogen byproduct: The hydrogen produced is either vented into space or, in some cases, used in the Sabatier reaction (described below) to help create more water.
Other Methods
- Delivered Supplies: Oxygen can also be delivered to the ISS in pressurized tanks via resupply missions from Earth. These tanks provide a backup or supplement to the electrolysis system.
- Chemical Oxygen Generators (Candles): These are emergency backup systems. They use a chemical reaction to release oxygen. Think of them as a last resort because they are not sustainable for long-term oxygen production.
- Sabatier Reaction: This process combines hydrogen (generated through electrolysis) with carbon dioxide (produced by the astronauts' breathing) to create water and methane. The water can then be used for electrolysis, and the methane is vented into space.
The Sabatier Reaction Equation
CO₂ + 4H₂ → CH₄ + 2H₂O
Why Multiple Methods Are Used
Having multiple oxygen generation methods provides redundancy and ensures the safety of the crew in case of equipment failure or unexpected events. Electrolysis is the primary method because it's more sustainable in the long run, but backup systems are crucial.
