A hypergolic propellant is a form of liquid propellant in which the fuel ignites spontaneously upon contact with an oxidizer, thereby eliminating the need for an ignition system. The easy start and restart capability of hypergolics make them ideal for spacecraft maneuvering systems. Also, since hypergolics remain liquid at normal temperatures, they don't pose the storage problems of cryogenic propellants. On the debit side, hypergolics are highly toxic and must be handled with extreme care.
Hypergolic fuels commonly include hydrazine, monomethyl hydrazine (MMH), and unsymmetrical dimethyl hydrazine (UDMH). The oxidizer is typically nitrogen tetroxide (N2O4) or nitric acid (HNO3).
Related category PROPELLANTS
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