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A hypergolic propellant is either of the two rocket propellants used in a hypergolic rocket engine, which spontaneously ignite when they come into contact. The two propellants are usually termed the "fuel" and the "oxidizer". Although hypergolic propellants are difficult to handle, a hypergolic engine is easy to control and very reliable.
Additional recommended knowledge
Derivation of the term
During World War II, rocket propellants were broadly classed as monergols, hypergols and non-hypergols. The ending ergol is a combination of Greek ergon or work, and Latin oleum or oil, later influenced by the German chemical suffix -ol from alcohol.
A hypergolic engine can be precisely controlled with only two valves, one for each propellant. This simplifies the control system and eliminates points of failure. With no complex starting procedure the thrust is predictable, i.e., the direction and velocity of the rocket will closely match calculations. For this reason, they were used by the returning LEM on the Apollo moon missions.
Hypergolic propellants are also less likely to detonate when starting, a potentially catastrophic condition known as a hard start.
Use in ICBMs
Hypergolic propellants have been used for intercontinental ballistic missiles, especially the Titan II, but because of difficulties in storing fuel, the trend in ICBMs has been to move toward solid-fuel boosters.
Common hypergolic propellants combinations
|This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Hypergolic_propellant". A list of authors is available in Wikipedia.|