Encyclopedia Astronautica
ClO3F/Hydrazine


Perchloryl fluoride was another of the extremely reactive and toxic oxidisers tested in the United States in the late 1950's. As in the other cases, it was found that the handling problems and safety risks outweighed the performance benefits. Hydrazine (N2H4) found early use as a fuel, but it was quickly replaced by UDMH. It is still used as a monopropellant for satellite station-keeping motors.

ClO3F is a colorless gas at atmospheric pressure and ambient temperature. The liquid is water-white. Perchloryl fluoride is normally supplied in 98 per cent concentration; moisture is limited to 0.02 weight per cent maximum. It is a moderately toxic, strongly oxidising agent. The mild sweetish odour is detectable at a concentration of 10 PPM in air. Perchloryl fluoride is permanently storable in common materials of construction. It is insensitive to detonation and mechanical shock. The anhydrous material is not corrosive; however, the presence of any moisture greatly increases the corrosiveness. There are several metals which are compatible with the "wet" oxidiser. There are a number of acceptable non-metals. Conventional lubricants should not be used.

Perchloryl fluoride may be prepared by the electrolysis of a mixture of sodium perchlorate (NaClO4) and hydrochloric acid (HF). 1959 production levels were very small; and the material had only recently become available in small commercial quantities at a price of $30 per kg. The projected price for large-scale production (5 million kg/year) was $ 3.30 per kg.

Hydrazine marketed for rocket propellant contains a minimum of 97 per cent N2H4, the other constituent being primarily water. Hydrazine is a clear, water-white, hygroscopic liquid. The solid is white. Hydrazine a toxic, flammable caustic liquid and a strong reducing agent. Its odour is similar that of ammonia, though less strong. It is slightly soluble in ammonia and methyl-amine. It is soluble in water, methanol, ethanol, UDMH, and ethylenediamine. Hydrazine is manufactured by the Raschig process, which involves the oxidation of ammonia to chloramine, either indirectly with aqueous sodium hypochlorite or directly with chlorine, and subsequent reaction of chloramine with excess ammonia. Raw materials include caustic, ammonia, and chlorine; these are high-tonnage, heavy chemicals. The cost of anhydrous hydrazine in drum quantities in 1959 was $ 7.00 per kg. The projected price, based on large-scale commercial production, was expected to be $ 1.00 per kg. Due to environmental regulations, by 1990 NASA was paying $ 17.00 per kg.

Oxidizer: ClO3F. Fuel: Hydrazine. Propellant Formulation: ClO3F/Hydrazine. Optimum Oxidizer to Fuel Ratio: 1.42. Temperature of Combustion: 3,390 deg K. Density: 1.22 g/cc. Oxidizer Density: 1.430 g/cc. Oxidizer Freezing Point: -146 deg C. Oxidizer Boiling Point: -47 deg C. Fuel Density: 1.008 g/cc. Fuel Freezing Point: 2.00 deg C. Fuel Boiling Point: 113 deg C.

Specific impulse: 295 s.
Specific impulse sea level: 295 s.

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