__NOTOC__ Aerozine 50 is a 50:50 mix by weight 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

unsymmetrical dimethylhydrazine Unsymmetrical dimethylhydrazine (UDMH; 1,1-dimethylhydrazine, НДМГ or codenamed Geptil) is a chemical compound with the formula H2NN(CH3)2 that is used as a rocket propellant. It is a colorless liquid, with a sharp, fishy, ammonia-like smell ...

(UDMH), originally developed in the late 1950s by

Aerojet General Aerojet was an American rocket and missile propulsion manufacturer based primarily in Rancho Cordova, California, with divisions in Redmond, Washington, Orange and Gainesville in Virginia, and Camden, Arkansas. Aerojet was owned by GenCorp. I ...

Corporation as a storable, high-energy,

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. The ...

fuel for the

Titan II The Titan II was an intercontinental ballistic missile (ICBM) developed by the Glenn L. Martin Company from the earlier Titan I missile. Titan II was originally designed and used as an ICBM, but was later adapted as a medium-lift space l ...

ICBM An intercontinental ballistic missile (ICBM) is a ballistic missile with a range greater than , primarily designed for nuclear weapons delivery (delivering one or more thermonuclear warheads). Conventional, chemical, and biological weapons c ...

rocket engines. Aerozine continues in wide use as a

rocket fuel 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 chemical ...

, typically with dinitrogen tetroxide as the

oxidizer An oxidizing agent (also known as an oxidant, oxidizer, electron recipient, or electron acceptor) is a substance in a redox chemical reaction that gains or " accepts"/"receives" an electron from a (called the , , or ). In other words, an oxid ...

, with which it is hypergolic. Aerozine 50 is more stable than hydrazine alone, and has a higher density and boiling point than UDMH alone. Pure hydrazine has a higher performance than Aerozine 50, but an unacceptable freezing point. By mixing pure hydrazine with UDMH, hydrazine's inconveniently high freezing point of 2 °C is lowered through

freezing-point depression Freezing-point depression is a drop in the minimum temperature at which a substance freezes, caused when a smaller amount of another, non- volatile substance is added. Examples include adding salt into water (used in ice cream makers and for ...

. In addition, UDMH is a more stable molecule; this reduces the chances of straight hydrazine decomposing unexpectedly, increasing safety and allowing the blend to be used as a coolant in regeneratively cooled engines. This type of fuel is mainly used for interplanetary probes and

spacecraft propulsion Spacecraft propulsion is any method used to accelerate spacecraft and artificial satellites. In-space propulsion exclusively deals with propulsion systems used in the vacuum of space and should not be confused with space launch or atmospheric e ...

. Unlike other more common propellants like

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 applica ...

liquid hydrogen Liquid hydrogen (LH2 or LH2) is the liquid state of the element hydrogen. Hydrogen is found naturally in the molecular H2 form. To exist as a liquid, H2 must be cooled below its critical point of 33 K. However, for it to be in a fully li ...

, Aerozine 50 is liquid at room temperature and can be stored in liquid state without significant boil off, thus making it a

storable propellant A propellant (or propellent) is a mass that is expelled or expanded in such a way as to create a thrust or other motive force in accordance with Newton's third law of motion, and "propel" a vehicle, projectile, or fluid payload. In vehicles, the e ...

better suited for long-term interplanetary missions. Aerozine 50 was largely used in

s and in their derivative launchers such as the core stages of the Titan-II/III/IV rocket because an ICBM requires long-term storage and launch on short notice; the rocket must be stored already fueled. This fuel was also used in

-derived upper stages, such as the

Delta II Delta II was an expendable launch system, originally designed and built by McDonnell Douglas. Delta II was part of the Delta rocket family and entered service in 1989. Delta II vehicles included the Delta 6000, and the two later Delta 7000 ...

rocket. It was also used by the

Apollo Lunar Module The Apollo Lunar Module (LM ), originally designated the Lunar Excursion Module (LEM), was the lunar lander spacecraft that was flown between lunar orbit and the Moon's surface during the United States' Apollo program. It was the first crewed ...

and the Service Propulsion System engine in the

Apollo CSM The Apollo command and service module (CSM) was one of two principal components of the United States Apollo spacecraft, used for the Apollo program, which landed astronauts on the Moon between 1969 and 1972. The CSM functioned as a mother ship ...

. The

Ariane 1 Ariane 1 was the first rocket in the Ariane family of expendable launch systems. It was developed and operated by the European Space Agency (ESA), which had been formed in 1973, the same year that development of the launcher had commenced. A ...

through

Ariane 4 The Ariane 4 was a European expendable space launch system, developed by the '' Centre national d'études spatiales'' (CNES), the French space agency, for the European Space Agency (ESA). It was manufactured by ArianeGroup and marketed by Ari ...

family used a related fuel, a mixture of 75% UDMH and 25% hydrazine hydrate called

UH 25 UH 25 is a fuel mixture for rockets. It was developed for the European Ariane 2–4 launch vehicles. UH 25 was developed after a disaster during flight 2 of the Ariane 1 rocket. During launch, one of the four Viking engines on the first stage deve ...

. Aerozine is ''not'' used as a

monopropellant Monopropellants are propellants consisting of chemicals that release energy through exothermic chemical decomposition. The molecular bond energy of the monopropellant is released usually through use of a catalyst. This can be contrasted with biprop ...

(a propellant that is not mixed with anything). The extra stability conferred by the methyl groups affects reactivity and thrust. In 1980, a leakage of Aerozine 50 resulted in the 1980 Damascus Titan missile explosion. The leak occurred due to puncture of the first-stage Titan fuel tank by a dropped tool. The initial explosion removed the 740-ton silo door and ejected the second stage and warhead out of the silo. The Titan's second stage exploded, and the

W53 The Mk/B53 was a high-yield nuclear bunker buster, bunker buster thermonuclear weapon developed by the United States during the Cold War. Deployed on Strategic Air Command bombers, the B53, with a nuclear weapon yield, yield of 9 megatons, was ...

warhead landed 30 meters from the silo portal without detonating or leaking fissile material.

Alternatives

Hydrazine may also be mixed with

monomethyl hydrazine Monomethylhydrazine (mono-methyl hydrazine, MMH) is a highly toxic, volatile hydrazine derivative with the chemical formula . It is used as a rocket propellant in bipropellant rocket engines because it is hypergolic with various oxidizers such as ...

(MMH). Because MMH is slightly denser, net performance is increased slightly. A potentially novel hypergolic alternative has been developed based on tertiary

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 substituen ...

azides – called CINCH (Competitive Impulse Non-Carcinogenic Hypergol) and the name of the compound is

2-Dimethylaminoethylazide 2-Dimethylaminoethylazide (DMAZ) is a liquid rocket fuel being investigated for use as a spacecraft propellent to replace the toxic, carcinogenic monomethylhydrazine. It is a member of the competitive impulse non-carcinogenic hypergol (CINCH) fami ...

Trivia

According to John D. Clark the propellant community disliked and ignored brandnames such as Aerojet's Aerozine, preferring its own

jargon Jargon is the specialized terminology associated with a particular field or area of activity. Jargon is normally employed in a particular Context (language use), communicative context and may not be well understood outside that context. The conte ...

of engineering acronyms and nicknames. This particular mixture was called "50–50".

References

External links

Encyclopedia Astronautica
{{GenCorp Rocket fuels Hydrazines

Alternatives

Trivia

See also

References

External links