UDMH
Encyclopedia
Unsymmetrical dimethylhydrazine (UDMH) (1,1-Dimethylhydrazine) is a toxic volatile hygroscopic clear liquid, with a sharp, fishy, ammoniacal smell typical for organic amine
s. It turns yellowish on exposure to air and absorbs oxygen
and carbon dioxide
. It mixes completely with water, ethanol
, and kerosene
. In concentration between 2.5% and 95% in air, its vapors are flammable. It is not sensitive to shock.
. UDMH is a derivative of hydrazine
and is sometimes referred to as a hydrazine. As a fuel, it is described in specification MIL-PRF-25604.
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 high density and cost. In some applications, such as the OMS in the Space Shuttle
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 Proton and Kosmos-3M are the most notable users of UDMH. The Titan
, GSLV
, and Delta rocket
families use a mixture of 50% hydrazine and 50% UDMH, called Aerozine 50
, in different stages.
Apart from its use as rocket fuel, UDMH is a nitrogen source in metalorganic vapour phase epitaxy
thin-film deposition.
and can explode in the presence of oxidisers. It is toxic and is absorbed through the skin. During the 1980s there was concern about the levels of UDMH in various foods being a cancer risk, especially for apple juice
.
Amine
Amines are organic compounds and functional groups that contain a basic nitrogen atom with a lone pair. Amines are derivatives of ammonia, wherein one or more hydrogen atoms have been replaced by a substituent such as an alkyl or aryl group. Important amines include amino acids, biogenic amines,...
s. It turns yellowish on exposure to air and absorbs oxygen
Oxygen
Oxygen is the element with atomic number 8 and represented by the symbol O. Its name derives from the Greek roots ὀξύς and -γενής , because at the time of naming, it was mistakenly thought that all acids required oxygen in their composition...
and carbon dioxide
Carbon dioxide
Carbon dioxide is a naturally occurring chemical compound composed of two oxygen atoms covalently bonded to a single carbon atom...
. It mixes completely with water, ethanol
Ethanol
Ethanol, also called ethyl alcohol, pure alcohol, grain alcohol, or drinking alcohol, is a volatile, flammable, colorless liquid. It is a psychoactive drug and one of the oldest recreational drugs. Best known as the type of alcohol found in alcoholic beverages, it is also used in thermometers, as a...
, and kerosene
Kerosene
Kerosene, sometimes spelled kerosine in scientific and industrial usage, also known as paraffin or paraffin oil in the United Kingdom, Hong Kong, Ireland and South Africa, is a combustible hydrocarbon liquid. The name is derived from Greek keros...
. In concentration between 2.5% and 95% in air, its vapors are flammable. It is not sensitive to shock.
Uses
UDMH is often used in hypergolic rocket fuels as a bipropellant in combination with the oxidizer nitrogen tetroxide and less frequently with IRFNA (red fuming nitric acid) or liquid oxygenLiquid oxygen
Liquid oxygen — abbreviated LOx, LOX or Lox in the aerospace, submarine and gas industries — is one of the physical forms of elemental oxygen.-Physical properties:...
. UDMH is a derivative of hydrazine
Hydrazine
Hydrazine is an inorganic compound with the formula N2H4. It is a colourless flammable liquid with an ammonia-like odor. Hydrazine is highly toxic and dangerously unstable unless handled in solution. Approximately 260,000 tons are manufactured annually...
and is sometimes referred to as a hydrazine. As a fuel, it is described in specification MIL-PRF-25604.
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
Liquid rocket
A liquid-propellant rocket or a liquid rocket is a rocket engine that uses propellants in liquid form. Liquids are desirable because their reasonably high density allows the volume of the propellant tanks to be relatively low, and it is possible to use lightweight pumps to pump the propellant from...
engines, despite its high density and cost. In some applications, such as the OMS in the Space Shuttle
Space Shuttle
The Space Shuttle was a manned orbital rocket and spacecraft system operated by NASA on 135 missions from 1981 to 2011. The system combined rocket launch, orbital spacecraft, and re-entry spaceplane with modular add-ons...
or maneuvering engines, monomethylhydrazine
Monomethylhydrazine
Monomethylhydrazine is a volatile hydrazine chemical with the chemical formula CH3 NH2. It is used as a rocket propellant in bipropellant rocket engines because it is hypergolic with various oxidizers such as nitrogen tetroxide and nitric acid...
is used instead due to its slightly higher specific impulse
Specific impulse
Specific impulse is a way to describe the efficiency of rocket and jet engines. It represents the derivative of the impulse with respect to amount of propellant used, i.e., the thrust divided by the amount of propellant used per unit time. If the "amount" of propellant is given in terms of mass ,...
.
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 Proton and Kosmos-3M are the most notable users of UDMH. The Titan
Titan (rocket family)
Titan was a family of U.S. expendable rockets used between 1959 and 2005. A total of 368 rockets of this family were launched, including all the Project Gemini manned flights of the mid-1960s...
, GSLV
Geosynchronous Satellite Launch Vehicle
The Geosynchronous Satellite Launch Vehicle is an expendable launch system operated by the Indian Space Research Organisation...
, and Delta rocket
Delta rocket
Delta is a versatile family of expendable launch systems that has provided space launch capability in the United States since 1960. There have been more than 300 Delta rockets launched, with a 95 percent success rate. Two Delta launch systems – Delta II and Delta IV – are in active use...
families use a mixture of 50% hydrazine and 50% UDMH, called Aerozine 50
Aerozine 50
Aerozine 50 is a 50/50 mix of hydrazine and unsymmetrical dimethylhydrazine . Originally developed in the late 1950s by Aerojet General Corporation as a storable, high-energy, hypergolic fuel for the Titan II ICBM rocket engines, Aerozine continues in wide use as a rocket fuel, typically with...
, in different stages.
Apart from its use as rocket fuel, UDMH is a nitrogen source in metalorganic vapour phase epitaxy
Metalorganic vapour phase epitaxy
Metalorganic vapour phase epitaxy , also known as organometallic vapour phase epitaxy or metalorganic chemical vapour deposition , is a chemical vapour deposition method of epitaxial growth of materials, especially compound semiconductors, from the surface reaction of organic compounds or...
thin-film deposition.
Safety
UDMH is toxic, a carcinogenCarcinogen
A carcinogen is any substance, radionuclide, or radiation that is an agent directly involved in causing cancer. This may be due to the ability to damage the genome or to the disruption of cellular metabolic processes...
and can explode in the presence of oxidisers. It is toxic and is absorbed through the skin. During the 1980s there was concern about the levels of UDMH in various foods being a cancer risk, especially for apple juice
Apple juice
Apple juice is a fruit juice manufactured by the maceration and pressing of apples. The resulting expelled juice may be further treated by enzymatic and centrifugal clarification to remove the starch and pectin, which holds fine particulate in suspension, and then pasteurized for packaging in...
.
External links
- http://www.astronautix.com/props/n2o4udmh.htm
- http://www.lr.tudelft.nl/live/pagina.jsp?id=e2984c9b-4864-46e0-992f-13ce92f3580b&lang=en