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.
Unsymmetrical Dimethylhydrazine ((CH3)2NNH2) became the storable liquid fuel of choice by the mid-1950's. Development of UDMH in the Soviet Union began in 1949. It is used in virtually all storable liquid rocket engines except for some orbital manoeuvring engines in the United States, where MMH has been preferred due to a slightly higher density and performance. Unsymmetrical dimethylhydrazine (UDMH) is 98 to 99 per cent pure and is described by Military Specification MIL-D-25604. The normally expected impurities are dimethylamine and water. UDMH is a clear, hygroscopic liquid which yellows on exposure to air. It absorbs oxygen and carbon dioxide. UDMH is a toxic volatile liquid. It exhibits the sharp ammoniacal or fishy odour which is characteristic of organic amines. It is completely miscible with water, ethanol, and most petroleum fuels. It is not shock sensitive. The vapours are flammable in air over 2.5 to 95 per cent concentration range. UDMH can be produced commercially by nitrosation of dimethylamine, to N-nitro-sodimethylrtmine, followed by reduction of the intermediate to UDMH and subsequent purification. UDMH can be prepared, also, by a modification of the Raschig process (see discussion of hydrazine), in which the chloramine intermediate is with dimethylamine rather than with ammonia. The price in 1959 for tank-car quantities was under $ 1.00 per kg. Engineering studies indicated a price of $ 1.00 per kg with large scale sustained production. But due to its toxic nature, production and transport costs soared in response to environmental regulations. By the 1980's NASA was paying $ 24.00 per kg.