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Unsymmetrical dimethylhydrazine (abbreviated as UDMH; also known as 1,1-dimethylhydrazine, heptyl or Geptil) is a chemical compound with the formula H 2 NN(CH 3) 2 that is primarily used as a rocket propellant. [4] At room temperature, UDMH is a colorless liquid, with a sharp, fishy, ammonia-like smell typical of organic amines.
Dimethylhydrazine is the name of two compounds with the molecular formula C 2 H 8 N 2.These are: unsymmetrical dimethylhydrazine (1,1-dimethylhydrazine), with both methyl groups bonded to the same nitrogen atom
The most common hypergolic fuels, hydrazine, monomethylhydrazine and unsymmetrical dimethylhydrazine, and oxidizer, nitrogen tetroxide, are all liquid at ordinary temperatures and pressures. They are therefore sometimes called storable liquid propellants. They are suitable for use in spacecraft missions lasting many years.
The reduction of benzenediazonium chloride with tin(II) chloride and hydrochloric acid provides phenylhydrazine. [2] 2,4-Dinitrophenylhydrazine is produced by the reaction of 1-chloro-2,4-dinitrobenzene with hydrazine. [2] Tetraphenylhydrazine is formed by the oxidation of diphenylamine with potassium permanganate in acetone. [2]
Aerozine 50 is a 50:50 mix by weight of hydrazine and unsymmetrical dimethylhydrazine (UDMH), [1] [2] developed in the late 1950s by Aerojet General Corporation as a storable, high-energy, hypergolic fuel for the Titan II ICBM rocket engines.
Both propellants are extremely dangerous individually: nitric acid is highly corrosive and releases toxic nitrogen dioxide during reactions, or even simply while exposed to air in its highly concentrated "red fuming" form, typically used as rocket propellant. UDMH is both toxic and corrosive.
The power for the thruster comes from the high pressure gas created during the decomposition reaction that allows a rocket nozzle to speed up the gas to create thrust. The most commonly used monopropellant is hydrazine (N 2 H 4, or H 2 N−NH 2), a compound unstable in the presence of a catalyst and which is also a strong reducing agent.
The first two reactions are extremely exothermic (the catalyst chamber can reach 800 °C in a matter of milliseconds, [28]) and they produce large volumes of hot gas from a small volume of liquid, [29] making hydrazine a fairly efficient thruster propellant with a vacuum specific impulse of about 220 seconds. [30]