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. 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.
Monomethylhydrazine (CH3NHNH2) is a storable liquid fuel that found favour in the United States for use in orbital spacecraft engines. Its advantages in comparison to UDMH are higher density and slightly higher performance. Monomethylhydrazine (MMH) is 95+ per cent pure, while the normally expected impurities are methylamine and water. MMH is a clear, water-white hygroscopic liquid which tends to turn yellow upon exposure to air. MMH is a toxic, volatile liquid which will react with carbon dioxide and oxygen. MMH has the typical sharp ammoniacal or fishy odour of amines. It is completely miscible in all proportions with hydrazine, water, and low molecular-weight alcohols. MMH is not sensitive to impact or friction; it is more stable than hydrazine on mild heating and similar to hydrazine in sensitivity to catalytic oxidation.
Monomethylhydrazine may be produced by a modified Raschig process; methylamine is substituted for ammonia in the reaction with chloramine. In general, substituted hydrazines may be prepared by the reaction of an alkylsulfate or halide with hydrazine. In 1959 the price for MMH was $ 15 per kg. It was projected that this would be reduced to $ 2.00 per kg in mass production. By 1990 NASA was actually paying $ 17.00 per kg due to stringent environmental protection regulations.