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 (N2O4) 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 risk 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. 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, 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 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.
Hydrazine may also be mixed with monomethyl hydrazine (MMH). Because MMH is slightly denser, net performance is increased slightly.[ citation needed ]
A potentially novel hypergolic alternative has been developed based on tertiary amine azides – called CINCH (Competitive Impulse Non-Carcinogenic Hypergol) and the name of the compound is 2-Dimethylaminoethylazide. [4] [5]
According to John D. Clark, the propellant community disliked and ignored brandnames such as Aerojet's Aerozine, preferring its own jargon of engineering acronyms and nicknames. This particular mixture was called "50–50". [2]
Titan was a family of United States expendable rockets used between 1959 and 2005. The Titan I and Titan II were part of the US Air Force's intercontinental ballistic missile (ICBM) fleet until 1987. The space launch vehicle versions contributed the majority of the 368 Titan launches, including all the Project Gemini crewed flights of the mid-1960s. Titan vehicles were also used to lift US military payloads as well as civilian agency reconnaissance satellites and to send interplanetary scientific probes throughout the Solar System.
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.
Unsymmetrical dimethylhydrazine (abbreviated as UDMH; also known as 1,1-dimethylhydrazine, heptyl or Geptil) is a chemical compound with the formula H2NN(CH3)2 that is primarily used as a rocket propellant. At room temperature, UDMH is a colorless liquid, with a sharp, fishy, ammonia-like smell typical of organic amines. Samples turn yellowish on exposure to air and absorb oxygen and carbon dioxide. It is miscible with water, ethanol, and kerosene. At concentrations between 2.5% and 95% in air, its vapors are flammable. It is not sensitive to shock.
Monomethylhydrazine (MMH) is a highly toxic, volatile hydrazine derivative with the chemical formula CH6N2. 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. As a propellant, it is described in specification MIL-PRF-27404.
A liquid-propellant rocket or liquid rocket uses a rocket engine burning liquid propellants. (Alternate approaches use gaseous or solid propellants.) Liquids are desirable propellants because they have reasonably high density and their combustion products have high specific impulse (Isp). This allows the volume of the propellant tanks to be relatively low.
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 launch vehicle to carry payloads to Earth orbit for the United States Air Force (USAF), National Aeronautics and Space Administration (NASA) and National Oceanic and Atmospheric Administration (NOAA). Those payloads included the USAF Defense Meteorological Satellite Program (DMSP), NOAA weather satellites, and NASA's Gemini crewed space capsules. The modified Titan II SLVs were launched from Vandenberg Air Force Base, California, up until 2003.
The Titan IIIC was an expendable launch system used by the United States Air Force from 1965 until 1982. It was the first Titan booster to feature large solid rocket motors and was planned to be used as a launcher for the Dyna-Soar, though the spaceplane was cancelled before it could fly. The majority of the launcher's payloads were DoD satellites, for military communications and early warning, though one flight (ATS-6) was performed by NASA. The Titan IIIC was launched exclusively from Cape Canaveral while its sibling, the Titan IIID, was launched only from Vandenberg AFB.
The highest specific impulse chemical rockets use liquid propellants. They can consist of a single chemical or a mix of two chemicals, called bipropellants. Bipropellants can further be divided into two categories; hypergolic propellants, which ignite when the fuel and oxidizer make contact, and non-hypergolic propellants which require an ignition source.
The UR-200 was an intercontinental ballistic missile (ICBM) developed by Vladimir Chelomey's OKB-52 in the Soviet Union. It was known during the Cold War by the NATO reporting name SS-10 Scrag and internally by the GRAU index 8K81. The design was authorized by the Decisions of the Central Committee of the CPSU of March 16 and August 1, 1961, and the draft project was finished in July 1962. It first flew on November 4, 1963, from the Baikonur Cosmodrome. The ninth and final flight was conducted on October 20, 1964.
UH 25 is a fuel mixture for rockets. It was developed for the European Ariane 2–4 launch vehicles.
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The Viking rocket engines were members of a series of bipropellant engines for the first and second stages of the Ariane 1 through Ariane 4 commercial launch vehicles, using storable, hypergolic propellants: dinitrogen tetroxide and UH 25, a mixture of 75% UDMH and 25% hydrazine.
The SM-68 Titan was the designation of two intercontinental ballistic missiles developed for the United States Air Force. The Titan I and Titan II missiles were operational between 1962 and 1987 during the Cold War. These missiles, particularly the Titan II, were the basis of the Titan family of space launch vehicles.
The Titan II GLV or Gemini-Titan II was an American expendable launch system derived from the Titan II missile, which was used to launch twelve Gemini missions for NASA between 1964 and 1966. Two uncrewed launches followed by ten crewed ones were conducted from Launch Complex 19 at the Cape Canaveral Air Force Station, starting with Gemini 1 on April 8, 1964.
The LR87 was an American liquid-propellant rocket engine used on the first stages of Titan intercontinental ballistic missiles and launch vehicles. Composed of twin motors with separate combustion chambers and turbopump machinery, it is considered a single unit and was never flown as a single combustion chamber engine or designed for this. The LR87 first flew in 1959.
Rocket propellant is used as reaction mass ejected from a rocket engine to produce thrust. The energy required can either come from the propellants themselves, as with a chemical rocket, or from an external source, as with ion engines.
Aestus is a hypergolic liquid rocket engine used on an upper stage of Ariane 5 family rockets for the orbital insertion. It features unique design of 132 coaxial injection elements causing swirl mixing of the MMH propellants with nitrogen tetroxide oxidizer. The pressure-fed engine allows for multiple re-ignitions.
A liquid apogee engine (LAE), or apogee engine, refers to a type of chemical rocket engine typically used as the main engine in a spacecraft.
The LR91 was an American liquid-propellant rocket engine, which was used on the second stages of Titan intercontinental ballistic missiles and launch vehicles. While the original version - the LR91-3 - ran on RP-1/LOX (as did the companion LR87-3) on the Titan I, the models that propelled the Titan II and later were switched to Aerozine 50/N2O4.
The A.M. Isayev Chemical Engineering Design Bureau, also known as KB KhimMash or just KBKhM, is a Russian rocket engine design and manufacturing company. It is located in the city of Korolyov. It started as the OKB-2 division of the NII-88 research institute, where A.Isaev directed the development of liquid rocket engines for ballistic missile submarines.