Oxygen in space, particularly aboard spacecraft like the International Space Station (ISS), isn't made from scratch, but rather extracted or generated from existing resources. The primary method relies on electrolysis.
Electrolysis: The Primary Method
Electrolysis is the process of using electricity to split water (H₂O) into its constituent elements: hydrogen (H₂) and oxygen (O₂). This process is a cornerstone of oxygen generation in space. The water used is often recycled from various sources including astronaut's perspiration, urine, and even reclaimed water vapor from the spacecraft's atmosphere. NASA's SpaceCraft Oxygen Recovery (SCOR) program focuses on efficient water recycling for oxygen generation.
- How it works: An electric current passed through the water breaks the chemical bonds, releasing oxygen gas that is then purified and supplied for breathing. The hydrogen byproduct can either be vented into space or used in fuel cells for power generation.
Other Methods
While electrolysis is the primary method, there are other supplementary techniques:
- Pressurized Oxygen Tanks: These provide a ready supply of pre-produced oxygen, particularly useful for emergencies or during critical phases of spaceflight.
- Solid Fuel Oxygen Generators (Oxygen Candles): These chemical devices release oxygen through a controlled chemical reaction. They offer a backup source but are not a primary means of oxygen production due to limitations on duration and potential waste products.
Addressing the Question's Implicit Assumption
The question implicitly assumes oxygen is created from nothing. This isn't the case. Oxygen is generated from readily available resources, primarily water, using established chemical and physical processes like electrolysis. The absence of free oxygen in the vacuum of space necessitates these onboard generation systems. Importantly, oxygen is not created in the sense of nuclear fusion, a process which creates elements.
