Unsymmetrical dimethylhydrazine (UDMH; 1,1-dimethylhydrazine, НДМГ or codenamed Geptil) is a

chemical compound A chemical compound is a chemical substance composed of many identical molecules (or molecular entities) containing atoms from more than one chemical element held together by chemical bonds. A molecule consisting of atoms of only one element ...

with the formula H₂NN(CH₃)₂ that is used as a

rocket propellant Rocket propellant is the reaction mass of a rocket. This reaction mass is ejected at the highest achievable velocity from a rocket engine to produce thrust. The energy required can either come from the propellants themselves, as with a chemic ...

. It is a colorless liquid, with a sharp, fishy, ammonia-like smell typical for organic

amine In chemistry, amines (, ) are compounds and functional groups that contain a basic nitrogen atom with a lone pair. Amines are formally derivatives of ammonia (), wherein one or more hydrogen atoms have been replaced by a substituent ...

s. Samples turn yellowish on exposure to air and absorb

oxygen Oxygen is the chemical element with the symbol O and atomic number 8. It is a member of the chalcogen group in the periodic table, a highly reactive nonmetal, and an oxidizing agent that readily forms oxides with most elements ...

and

carbon dioxide Carbon dioxide ( chemical formula ) is a chemical compound made up of molecules that each have one carbon atom covalently double bonded to two oxygen atoms. It is found in the gas state at room temperature. In the air, carbon dioxide is t ...

. It is miscible with water,

ethanol Ethanol (abbr. EtOH; also called ethyl alcohol, grain alcohol, drinking alcohol, or simply alcohol) is an organic compound. It is an alcohol with the chemical formula . Its formula can be also written as or (an ethyl group linked to a ...

, and

kerosene Kerosene, paraffin, or lamp oil is a combustible hydrocarbon liquid which is derived from petroleum. It is widely used as a fuel in aviation as well as households. Its name derives from el, κηρός (''keros'') meaning " wax", and was re ...

. In concentration between 2.5% and 95% in air, its vapors are flammable. It is not sensitive to shock. Symmetrical dimethylhydrazine, 1,2-dimethylhydrazine is also known but is not as useful.

Production

UDMH is produced industrially by two routes. Based on the

Olin Raschig process The Olin Raschig process is a chemical process for the production of hydrazine. The main steps in this process, patented by German chemist Friedrich Raschig in 1906 and one of three reactions named after him, are the formation of monochloramine fro ...

, one method involves reaction of

monochloramine Monochloramine, often called chloramine, is the chemical compound with the formula NH2Cl. Together with dichloramine (NHCl2) and nitrogen trichloride (NCl3), it is one of the three chloramines of ammonia. It is a colorless liquid at its melting p ...

with

dimethylamine Dimethylamine is an organic compound with the formula (CH3)2NH. This secondary amine is a colorless, flammable gas with an ammonia-like odor. Dimethylamine is commonly encountered commercially as a solution in water at concentrations up to arou ...

giving 1,1-dimethylhydrazinium chloride: :(CH₃)₂NH + NH₂Cl → (CH₃)₂NNH₂ ⋅ HCl In the presence of suitable catalysts, acetylhydrazine can be N-dimethylated using

formaldehyde Formaldehyde ( , ) ( systematic name methanal) is a naturally occurring organic compound with the formula and structure . The pure compound is a pungent, colourless gas that polymerises spontaneously into paraformaldehyde (refer to section ...

and hydrogen to give the N,N-dimethyl-N'-acetylhydrazine, which can subsequently be hydrolyzed: :CH₃C(O)NHNH₂ + 2CH₂O + 2H₂ → CH₃C(O)NHN(CH₃)₂ + 2H₂O :CH₃C(O)NHN(CH₃)₂ + H₂O → CH₃COOH + H₂NN(CH₃)₂

Uses

UDMH is often used in

hypergolic A hypergolic propellant is a rocket propellant combination used in a rocket engine, whose components spontaneously ignite when they come into contact with each other. The two propellant components usually consist of a fuel and an oxidizer. T ...

rocket fuels as a bipropellant in combination with the oxidizer nitrogen tetroxide and less frequently with IRFNA (inhibited red fuming nitric acid) or

liquid oxygen Liquid oxygen—abbreviated LOx, LOX or Lox in the aerospace, submarine and gas industries—is the liquid form of molecular oxygen. It was used as the oxidizer in the first liquid-fueled rocket invented in 1926 by Robert H. Goddard, an app ...

. UDMH is a derivative of

hydrazine Hydrazine is an inorganic compound with the chemical formula . It is a simple pnictogen hydride, and is a colourless flammable liquid with an ammonia-like odour. Hydrazine is highly toxic unless handled in solution as, for example, hydrazine ...

and is sometimes referred to as a hydrazine. As a fuel, it is described in specification MIL-PRF-25604 in the United States. UDMH is stable and can be kept loaded in rocket fuel systems for long periods, which makes it appealing for use in many liquid rocket engines, despite its cost. In some applications, such as the OMS in the

Space Shuttle The Space Shuttle is a retired, partially reusable low Earth orbital spacecraft system operated from 1981 to 2011 by the U.S. National Aeronautics and Space Administration (NASA) as part of the Space Shuttle program. Its official program n ...

or maneuvering engines, monomethylhydrazine is used instead due to its slightly higher specific impulse. In some kerosene-fueled rockets, UDMH functions as a starter fuel to start combustion and warm the rocket engine prior to switching to kerosene. UDMH has higher stability than hydrazine, especially at elevated temperatures, and can be used as its replacement or together in a mixture. UDMH is used in many European, Russian, Indian, and Chinese rocket designs. The Russian

SS-11 Sego The UR-100 (russian: УР-100) was an intercontinental ballistic missile (ICBM) developed and deployed by the Soviet Union from 1966 to 1996. UR () in its designation stood for Universal Rocket (russian: links=no, Универсальная � ...

(aka 8K84) ICBM, SS-19 Stiletto (aka 15A30) ICBM,

Proton A proton is a stable subatomic particle, symbol , H+, or 1H+ with a positive electric charge of +1 ''e'' elementary charge. Its mass is slightly less than that of a neutron and 1,836 times the mass of an electron (the proton–electron mass ...

, Kosmos-3M, R-29RMU2 Layner, R-36M, Rokot (based on 15A30) and the Chinese Long March 2F are the most notable users of UDMH (which is referred to as "heptyl" Soviet_era.html"_;"title="USSR.html"_;"title="odename_from_USSR">Soviet_era">USSR.html"_;"title="odename_from_USSR">Soviet_eraby_Russian_engineers)._The_ Soviet_era.html"_;"title="USSR.html"_;"title="odename_from_USSR">Soviet_era">USSR.html"_;"title="odename_from_USSR">Soviet_eraby_Russian_engineers)._The_Titan_(rocket_family)">Titan_ Titan_most_often_refers_to: *_Titan_(moon),_the_largest_moon_of_Saturn *_Titans,_a_race_of_deities_in_Greek_mythology Titan_or_Titans_may_also_refer_to: _Arts_and_entertainment _Fictional_entities _Fictional_locations *_Titan_in_fiction,_fictiona_...

Production

Uses

Safety

See also

References

External links