Monomethylhydrazine

Monomethylhydrazine (MMH) is a volatile hydrazine with the chemical formula CH3N2H3. It is used as a rocket fuel in bipropellant rocket engines.

MMH is very commonly applied notably in the OMS (orbital maneuvering system) engines of the NASA Space Shuttle. The compound is toxic and carcinogenic, but easily stored in space providing moderate performance for very low tankage and fuel maintenance system weight. Recently the European Space Agency has attempted to seek new options in terms of propellant/oxidiser combinations in order to avoid chemicals such as this.

MMH and its relative UDMH (unsymmetrical dimethyl hydrazine) have a key advantage that they are stable enough to be used in regeneratively cooled rocket engines.

It is also found in trace amounts in raw Agaricus bisporus, the common mushroom in grocery stores, and in most members of the mushroom genus Gyromitra, most notably the False Morel (Gyromitra esculenta).