How do spacecrafts propel through space where there is no oxygen for combustion?
In: 4
Three pieces:
1. There’s nothing to slow them down, so once they get going they can just coast forever. A spacecraft like Voyager hasn’t had propulsion in decades, but is still rapidly flying away from the solar system.
2. Not all space propulsion systems are based on burning things. Ultimately for a spacecraft propulsion system to work it needs to eject something with momentum. To do that takes energy. Combustion is convenient since you wind up with hot exhaust that has both momentum and energy, so it’s a nicely packaged way of getting lots of thrust in space, but there are other systems that are better in other settings. For example, one may use solar panels to generate electricity, then use that electricity to shoot some Xenon gas at *incredible* velocities. This winds up being a lot more efficient, and oxygen is never needed.
3. The rockets that do use oxygen bring it along with them. It’s effectively just another fuel–you get one tank for oxygen (typically liquefied for the sake of space) and one tank that contains something like Kerosene or liquefied hydrogen.
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