__NOTOC__ Aerozine 50 is a 50:50 mix by weight of hydrazine and unsymmetrical dimethylhydrazine (UDMH), developed in the late 1950s by Aerojet General Corporation as a storable, high-energy, hypergolic fuel for the Titan II

ICBM An intercontinental ballistic missile (ICBM) is a ballistic missile with a range (aeronautics), range greater than , primarily designed for nuclear weapons delivery (delivering one or more Thermonuclear weapon, thermonuclear warheads). Conven ...

rocket engines. Aerozine continues in wide use as a rocket fuel, typically with dinitrogen tetroxide () as the oxidizer, with which it is hypergolic. Aerozine 50 is more stable than hydrazine alone, and has a higher

density Density (volumetric mass density or specific mass) is the ratio of a substance's mass to its volume. The symbol most often used for density is ''ρ'' (the lower case Greek letter rho), although the Latin letter ''D'' (or ''d'') can also be u ...

and

boiling point The boiling point of a substance is the temperature at which the vapor pressure of a liquid equals the pressure surrounding the liquid and the liquid changes into a vapor. The boiling point of a liquid varies depending upon the surrounding envi ...

than UDMH alone. Pure hydrazine has a higher performance than Aerozine 50, but an inconvenient

freezing point The melting point (or, rarely, liquefaction point) of a substance is the temperature at which it changes state of matter, state from solid to liquid. At the melting point the solid and liquid phase (matter), phase exist in Thermodynamic equilib ...

of 2 °C. A mix of hydrazine and UDMH has a far lower freezing point due to

freezing-point depression Freezing-point depression is a drop in the maximum temperature at which a substance freezing, freezes, caused when a smaller amount of another, non-Volatility (chemistry), volatile substance is added. Examples include adding salt into water (u ...

. In addition, UDMH is a more stable molecule; this reduces the

risk In simple terms, risk is the possibility of something bad happening. Risk involves uncertainty about the effects/implications of an activity with respect to something that humans value (such as health, well-being, wealth, property or the environ ...

of pure 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 or liquid hydrogen, Aerozine 50 is liquid at room temperature and can be stored in liquid state without significant boil off, thus making it a storable propellant 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, and sometimes known as the Thorad Delta 1. Delta II was part of the Delta rocket family, derived directly from the Delta 3000, and entered service in ...

rocket. It was also used by the Apollo Lunar Module 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), Apollo spacecraft, used for the Apollo program, which landed astronauts on the Moon between 1969 and 1972. The CSM functi ...

. The Ariane 1 through Ariane 4 family used a related fuel, a mixture of 75% UDMH and 25% hydrazine hydrate called UH 25. Aerozine is ''not'' used as a monopropellant (a propellant that is not mixed with anything). The extra stability conferred by the methyl groups affects reactivity and

thrust Thrust is a reaction force described quantitatively by Newton's third law. When a system expels or accelerates mass in one direction, the accelerated mass will cause a force of equal magnitude but opposite direction to be applied to that ...

. In 1980, an accidental 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 A warhead is the section of a device that contains the explosive agent or toxic (biological, chemical, or nuclear) material that is delivered by a missile, rocket (weapon), rocket, torpedo, or bomb. Classification Types of warheads include: *E ...

out of the silo. The Titan's second stage exploded, and the W53 warhead landed 30 meters from the silo portal without detonating or leaking fissile material.

Alternatives

Hydrazine may also be mixed with monomethyl hydrazine (MMH). Because MMH is slightly denser, net performance is increased slightly. With 2-Dimethylaminoethylazide, a potentially novel hypergolic alternative compound has been developed based on tertiary amine azides called CINCH (Competitive Impulse Non-Carcinogenic Hypergol).

Trivia

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

jargon Jargon, or technical language, 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 ...

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

Further reading

External links