Topic summary
Rocket fuel
Extracted from the Wikipedia article Rocket propellant.
Compressed gas
For low-performance applications, such as attitude control jets, compressed gases such as nitrogen have been employed. Energy is stored in the pressure of the inert gas. However, due to the low density of all practical gases and high mass of the pressure vessel required to contain it, compressed gases see little current use. One application of compressed gas as rocket fuel is in water rockets; compressed air is used to push the reaction mass, water, out of the plastic bottle that serves as the body of the rocket.