Rocket Propellant - Inert Propellants

Inert Propellants

Some rocket designs have their propellants obtain their energy from non chemical or even external sources. For example water rockets use the compressed gas, typically air, to force the water out of the rocket.

Solar thermal rockets and Nuclear thermal rockets typically propose to use liquid hydrogen for an I_sp (Specific Impulse) of around 600–900 seconds, or in some cases water that is exhausted as steam for an I_sp of about 190 seconds.

Additionally for low performance requirements such as attitude jets, inert gases such as nitrogen have been employed.