RD-100 / RD-101 Credit - © Dietrich Haeseler

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. 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.

Alcohol (C2H5OH) was the fuel used for the German V-2 rocket, and the first derivative rocket engines in the United States, Soviet Union, and China used it as well. Better performance was achieved by increasing the alcohol concentration in the post-war engines. But after better-performance rocket-grade kerosene was developed by Rocketdyne in the REAP program of 1953, use of alcohol was abandoned. Ethyl alcohol, or ethanol, has wide commercial uses in both the chemical and the spirits industries and is produced commercially in large quantities. It is a clear, water-white, mobile liquid with the characteristic alcohol odour. It is an excellent solvent; special lubricants must be used. Materials of construction used for methanol are also used for ethanol. Like methanol, ethanol forms explosive mixtures with air or with oxidisers. Denaturants added to the alcohol can cause poisoning, blindness, and death. (Despite this, the Russians liked to call their early missiles 'drunk rockets'. Ethyl alcohol is produced by fermentation of sugars (glucose) or hydrolysed starches. The majority of the ethyl alcohol for solvent use is made by the hydrolysis of ethyl sulphate, which results from the addition of sulphuric acid to ethylene. Ethyl alcohol forms an azeotrope with water; this solution is 95.6 per cent ethyl alcohol. Absolute alcohol is made by azeotropic distillation with benzene. The estimated 1959 United States production was 1.6 million tonnes (50 per cent by volume). The price of absolute alcohol, tax-free, in tank-car quantities was $ 0.16 per kg. Density varies: 0.87 g/cc for 75% alcohol; 0.80 g/cc for 92.5% alcohol; to 0.79 g/cc for 96% alcohol.