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. 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 and boiling point than UDMH alone.
Pure hydrazine has a higher performance than Aerozine 50, but an inconvenient freezing point of 2 °C.[3] A mix of hydrazine and UDMH has a far lower freezing point due to freezing-point depression. 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. 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 ICBMs 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 ICBM-derived upper stages, such as the Delta II rocket. It was also used by the Apollo Lunar Module and the Service Propulsion System engine in the Apollo CSM. 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.
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 warhead landed 30 meters from the silo portal without detonating or leaking fissile material.
^"Aerozine50 Specifications & DOT Shipping Information" (PDF). NASA. October 5, 2006. Archived from the original (PDF) on March 26, 2014.
^Clark, J. D.; Asimov, Isaac (1972). Ignition! an informal history of liquid rocket propellants. Rutgers University Press. p. 45. ISBN 978-0-8135-0725-5.
^Sutton, George P. (2006). History of liquid propellant rocket engines. Reston, Va.: American Institute of Aeronautics and Astronautics. p. 383. ISBN 1-56347-649-5. OCLC 63680957.
Aerozine50 is a 50:50 mix by weight of hydrazine and unsymmetrical dimethylhydrazine (UDMH), developed in the late 1950s by Aerojet General Corporation...
the first-stage fuel tank, causing it to leak a cloud of its Aerozine50 fuel. Aerozine50 is hypergolic with the Titan II's oxidizer, dinitrogen tetroxide...
I, the models that propelled the Titan II and later were switched to Aerozine50/N2O4. This engine was vacuum optimized and ran the gas-generator cycle...
critical usage of this engine during the Apollo program. This version used Aerozine50 (a 1:1 mix of UDMH and hydrazine) as fuel and nitrogen tetroxide (N2O4)...
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the Titan II; all engines in the Apollo Lunar Module. Aerozine50 is a mixture of 50% UDMH and 50% straight hydrazine (N2H4).: 45 Monomethylhydrazine...
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LGM-25C, the Titan II was the largest USAF missile at the time and burned Aerozine50 and nitrogen tetroxide (NTO) rather than RP-1 and LOX. The Titan III...
URSA 25 R TRW Inc. Aerozine50 or MMH N2O4 111 25 URSA 100 R TRW Inc. Aerozine50 or MMH N2O4 445 100 URSA 200 R TRW Inc. Aerozine50 or MMH N2O4 890 200...
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engine flown on the Boeing X-51 hypersonic demonstration vehicle. AJ10 (Aerozine50/N2O4) – Second stage engine for the Delta II, used as the Orbital Maneuvering...
Aerosystems for use in the Apollo Lunar Module ascent stage. It used Aerozine50 fuel, and N 2O 4 oxidizer. Rocketdyne provided the injector system, at...
ascent mission mode, The engine selected was the AJ10-137, which used Aerozine50 as fuel and nitrogen tetroxide (N2O4) as oxidizer to produce 20,500 lbf...
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N2O4 / Aerozine50 Second stage Powered by 1 LR87-AJ-5 Maximum thrust 445 kN (100,000 lbf) Burn time 205 seconds Propellant N2O4 / Aerozine50 Third stage...
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