Better Densification of Cryogenic Liquid Rocket Propellants

An improved system for densifying (by cooling) the liquid hydrogen and liquid oxygen used as propellants for the space shuttle has been proposed. These propellant liquids are cooled to minimize the sizes of tanks needed to store them and to reduce maximum operating pressures. The proposed system would densify these liquids 7 to 8 percent more efficiently than does the present propellant-densification system, and would reduce the absolute vapor pressure from about 15 psi (≈0.1 MPa) to about 1.5 psi (≈10 kPa). Sizing analysis indicates that the combination of the increase in density and the decrease in vapor pressure would reduce the weight of the space shuttle by 10 to 20 percent. Similar reductions in the required volumes and weights of tanks for storing cryogenic liquids could be beneficial in any industry in which the sizes of such tanks are cost factors.