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. It had big drawbacks, however - it was highly cryogenic, and it had a very low density, making for large tanks. The technology was transferred to the Centaur rocket stage program, and by the mid-1960's the United States was flying the Centaur and Saturn upper stages using the fuel. It was adopted for the core of the space shuttle, and Centaur stages still fly today.