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A hypergolic propellant combination used in a rocket engine is one where the propellants spontaneously ignite when they come into contact with each other. The two propellant components usually consist of a fuel and an oxidizer. Although commonly used hypergolic propellants are difficult to handle because of their extreme toxicity and/or corrosiveness, they can be stored as liquids at room temperature and hypergolic engines are easy to ignite reliably and repeatedly. In contemporary usage, the terms "hypergol" or "hypergolic propellant" usually mean the most common such propellant combination, dinitrogen tetroxide plus hydrazine and/or its relatives monomethylhydrazine and unsymmetrical dimethylhydrazine. == History == Soviet rocket engine researcher Valentin Glushko experimented with hypergolic fuel as early as 1931. It was initially used for "chemical ignition" of engines, starting kerosene/nitric acid engines with an initial charge of phosphorus dissolved in carbon disulfide. Starting in 1935, Prof. O. Lutz of the German Aeronautical Institute experimented with over 1000 self-igniting propellants. He assisted the Walter Company with the development of C-Stoff which ignited with concentrated hydrogen peroxide. BMW developed engines burning a hypergolic mix of nitric acid with various combinations of amines, xylidines and anilines.〔O. Lutz, in History of German Guided Missiles Development, 1957〕 Hypergolic propellants were discovered independently, for the third time, in the U.S. by GALCIT and Navy Annapolis researchers in 1940. They developed engines powered by aniline and nitric acid.〔Sutton, George P., History of Liquid Propellant Rocket Engines〕 Robert Goddard, Reaction Motors and Curtiss-Wright worked on aniline/nitric acid engines in the early 1940s, for small missiles and jet assisted take-off (JATO).〔The Papers of Robert H. Goddard〕 In Germany from the mid-1930s through World War II, rocket propellants were broadly classed as monergols, hypergols, non-hypergols and lithergols. The ending ''ergol'' is a combination of Greek ''ergon'' or work, and Latin ''oleum'' or oil, later influenced by the chemical suffix ''-ol'' from alcohol.〔"-ergol", ''Oxford English Dictionary''〕 Monergols were monopropellants, while non-hypergols were bipropellants which required external ignition, and lithergols were solid/liquid hybrids. Hypergolic propellants (or at least hypergolic ignition) were far less prone to hard starts than electric or pyrotechnic ignition. The "hypergole" terminology was coined by Dr. Wolfgang Nöggerath, at the Technical University of Brunswick, Germany.〔Botho Stüwe, Peene Münde West, Weltbildverlag ISBN 3-8289-0294-4, 1998 page 220, German〕 The only rocket-powered fighter ever deployed, the Messerschmitt Me 163B ''Komet'', depended on its methanol/hydrazine fueled, high test peroxide consuming HWK 109-509A rocket motor, using its hypergolic propellants for its fast climb and quick-hitting tactics, at the cost of having a supremely volatile power system capable of causing a massive explosion, with any degree of inattention at any time. Other proposed combat rocket fighters like the Heinkel ''Julia'' and reconnaissance aircraft like the DFS 228 were meant to use the Walter 509 series of rocket motors, but besides the Me 163, only the Bachem Ba 349 ''Natter'' vertical launch expendable fighter was ever flight-tested with the Walter rocket propulsion system as its primary sustaining thrust system for military-purpose aircraft. The earliest ballistic missiles, such as the Soviet R-7 that launched Sputnik 1 and the U.S. Atlas and Titan-1, used kerosene and liquid oxygen. Although they are preferred in space launchers, the difficulties of storing a cryogen like liquid oxygen in a missile that had to be kept launch ready for months or years at a time led to a switch to hypergolic propellants in the U.S. Titan II and in most Soviet ICBMs such as the R-36. But the difficulties of such corrosive and toxic materials, including leaks and explosions in Titan-II silos, led to their near universal replacement with solid-fuel boosters, first in Western submarine-launched ballistic missiles and then in land-based U.S. and Soviet ICBMs.〔Clark (1972), p.214〕 The trend among western space launch agencies is away from large hypergolic rocket engines and toward hydrogen/oxygen engines with higher performance. Ariane 1 through 4, with their hypergolic first and second stages (and optional hypergolic boosters on the Ariane 3 and 4) have been retired and replaced with the Ariane 5, which uses a first stage fueled by liquid hydrogen and liquid oxygen. The Titan II, III and IV, with their hypergolic first and second stages, have also been retired. Hypergolic rockets are still widely used in upper stages when multiple burn-coast periods are required. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Hypergolic propellant」の詳細全文を読む スポンサード リンク
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