1. Solid propellants – These are used for very large thrusts, eg to escape Earth’s orbit. Solid propellant motors are very simple to design, though once ignited, they can’t be shut off and so burn until exhausted.
2. Hybrid propellants – These are a combination of solid and liquid propellants, with a liquid oxidiser injected into a solid fuel. Hybrids are a lot cleaner than solid rockets.
3. Hydrazine – Commonly known as hypergolic rocket fuel, hydrazine simply needs nitric acid in order to ignite and is frequently used for propulsion when out in space.
4. Petroleum – Don’t be fooled, you wouldn’t fuel your car with this stuff! Rocket-grade petroleum is called RP-1 and consists of a highly refined kerosene mixed with liquid oxygen.
5. Alcohol – Early rockets, such as Germany’s V-2 missile in WWII, used a mix of liquid oxygen and ethyl alcohol, although more efficient fuels were discovered soon after.