Fuel

Fuel, also called propellant, is a key part to propel a craft. All fuels are burned in the engine except xenon gas which is simply accelerated by electromagnetic forces.

Fuel either references all resources which are used by engines or it describes only the resource which gets mixed with a form of oxygen. The later definition describes:

• Liquid fuel
• Solid fuel
• Xenon gas
• Monopropellant

The first definition would also include oxidizer and intake air which both supply the oxygen to burn the liquid fuel. In wider terms also electric charge may defined by the fuel definition, as that resource is required by ion engines to accelerate the xenon gas.