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. 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. 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. Better performance was achieved by increasing the alcohol concentration in the post-war engines. 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.