The fuel that SpaceX uses in space is different depending on which SpaceX you're referring to.
The Falcon 9 SpaceX uses rocket grade kerosene or RP-1 and liquid oxygen in a gas generator power cycle.
The SpaceX Starship uses liquid methane and liquid oxygen as fuel and propellants.
And the SpaceX Raptor uses liquid methane and liquid oxygen and is a mixture known as methalox.
Methane is a cleaner and more efficient fuel than kerosene is and it also produces around 10 percent more thrust than kerosene.
Methane is also relatively simple to work with and can also be produced on Mars.
Propulsion does work in space as spacecraft and rockets use a propulsion method and principle called reaction mass which generates thrust by expelling hot gases from their engines.
This is what propels them forward even in the vacuum of space and is based on Newton's Third Law of Motion.
The force of the expelled gases push the spacecraft in the opposite direction and allows for movement without requiring air to push against.
Turbine engines and normal propellers use air from the atmosphere as their working fluid, however rockets use the combustion exhaust gases.
And in out space there is no atmosphere so normal turbines and normal propellers don't work in space.
This is why rockets work in space but turbine engines and propellers don't work in space like they do on earth.
The fuel that satellites use is hydrazine based fuel which is the satellites primary propellant.
However research is ongoing to develop a less toxic fuel due to it's highly toxic nature.
Hydrazine based fuel is often used for stationkeeping maneuvers and orbital adjustments.
Once the satellite is in it's position above earth in space the satellite requires a method of propulsion to make sure the satellite can move if it needs to.
The satellite also needs to be able to avoid space debris and compensate for drag over time as well as be able to de-orbit itself after the mission is over.
The satellites use a highly toxic hydrazine based fuel for this propellant fuel.
Hydrazine based fuel is a type of highly toxic propellant that uses hydrazine (N2H4) as its primary fuel source, commonly used in rocket propulsion systems due to its high energy density, stability, and ability to ignite spontaneously when exposed to a catalyst, making it ideal for applications like satellite thrusters and spacecraft maneuvering.
While hydrazine based fuel is a great fuel source for satellites in space, hydrazine is highly toxic and requires strict handling procedures due to its hazardous nature