Encyclopedia Astronautica

Redstone engine
Credit: NASA
Liquid oxygen was the earliest, cheapest, safest, and eventually the preferred oxidiser for large space launchers. Its main drawback is that it is moderately cryogenic, and therefore not suitable for military uses where storage of the fuelled missile and quick launch are required. Hydyne was a propellant blend pushed rather vigorously by the Redstone arsenal in the late 1950's, but it found little application. Hydyne, which is also known as MAF-4, is a 60 per cent, by weight, mixture of UDMH and 40 weight percent diethyltrianine (DETA).

Liquid oxygen, as normally supplied, is of 99.5 percent purity and is covered in the United States by Military Specification MIL-P-25508. High purity liquid oxygen has a light blue colour and is transparent. It has no characteristic odour. Liquid oxygen does not burn, but will support combustion vigorously. The liquid is stable; however, mixtures of fuel and liquid oxygen are shock-sensitive. Gaseous oxygen can form mixtures with fuel vapours that can be exploded by static electricity, electric spark, or flame. Liquid oxygen is obtained from air by fractional distillation. The 1959 United. States production of high-purity oxygen was estimated at nearly 2 million tonnes. The cost of liquid oxygen, at that time, ex-works, was $ 0.04 per kg. By the 1980's NASA was paying $ 0.08 per kg.

The normally occurring impurities are dimethylamine, beta-aminoethyl-N-piperazine, and water. Hydyne is a clear, colourless liquid which may become discoloured on exposure to air during storage. Both UDMH and DETA have an ammoniacal odour; the odour is not so sharp or fishy as that of UDMH. Hydyne is a hygroscopic liquid which will absorb carbon dioxide and oxygen from air. It is completely miscible with water and ethanol; the solubility of gasoline and JP-4 in Hydyne are somewhat limited. It forms flammable explosive mixtures with air. Amines generally yellow during storage due to oxidation followed by polymerisation induced by air (O2) reaction is believed to form an intermediate amine oxide which undergoes polymerisation. The cost of Hydyne in 1959 was $ 0.80 per kg.

Oxidizer: LOX. Fuel: Hydyne. Propellant Formulation: LOX/Hydyne. Optimum Oxidizer to Fuel Ratio: 1.73. Temperature of Combustion: 3,585 deg K. Density: 1.02 g/cc. Oxidizer Density: 1.140 g/cc. Oxidizer Freezing Point: -219 deg C. Oxidizer Boiling Point: -183 deg C. Fuel Density: 0.860 g/cc. Fuel Freezing Point: -84 deg C. Fuel Boiling Point: 64 deg C.

Specific impulse: 359 s.
Specific impulse sea level: 306 s.

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Associated Engines
  • A-7 Rocketdyne Lox/Hydyne rocket engine. 416.2 kN. Out of Production. Version of Redstone engine for Jupiter-C test vehicle, with Hydyne fuel and 140 seconds burn time. Flew 1956-1959. Gas generator, pump-fed. Thrust 370 kN at sea level. Isp=265s. More...

Associated Stages
  • Jupiter C Lox/Hydyne propellant rocket stage. Loaded/empty mass 28,430/3,890 kg. Thrust 416.18 kN. Vacuum specific impulse 265 seconds. Redstone missile, stretched, modified with different propellants to serve as first stage of IRBM nose cone/orbital test vehicle. More...

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