Common propellant combinations used for liquid propellant rockets include:
Ø Red fuming nitric acid (RFNA) and kerosene or RP-1
Ø RFNA and Unsymmetrical dimethyl hydrazine (UDMH) Dinitrogen tetroxide and UDMH, MMH and/or hydrazine Liquid oxygen and kerosene or RP-1
Ø Liquid oxygen and liquid hydrogen
Ø Liquid oxygen and ethanol
Ø Hydrogen peroxide and alcohol or RP-1
Ø Chlorine pentafluoride and hydrazine
Common monopropellant used for liquid rocket engines include:
Ø Hydrogen peroxide
Ø Red fuming nitric acid (RFNA)
Introducing propellant into a combustion chamber
Rocket propellant is mass that is stored, usually in some form of propellant tank, prior to being ejected from a rocket engine in the form of a fluid jet to produce thrust.
Chemical rocket propellants are most commonly used, which undergo exothermic chemical reactions which produce hot gas which is used by a rocket for propulsive purposes. Alternatively, a chemically inert reaction mass can be heated using a high- energy power source via a heat exchanger, and then no combustion chamber is used.
A solid rocket motor:
Solid rocket propellants are prepared as a mixture of fuel and oxidizing components called 'grain' and the propellant storage casing effectively becomes the combustion chamber. Liquid-fueled rockets typically pump separate fuel and oxidiser components into the combustion chamber, where they mix and burn. Hybrid rocket engines use a combination of solid and liquid or gaseous propellants. Both liquid and hybrid rockets use injectors to introduce the propellant into the chamber. These are often an array of simple jets- holes through which the propellant escapes under pressure; but sometimes may be more complex spray nozzles. When two or more propellants are injected the jets usually deliberately collide the propellants as this breaks up the flow into smaller droplets that burn more easily.