Hydrogen Reliquefaction in Earth Orbit

Abstract

The effectiveness of many earth-orbit missions of long duration depends on the conservation of cryogenic propellants. For storage periods of the order of several days to several months, the reduction of cryogen boil-off losses is a critical problem. Present insulation techniques are inadequate beyond a few hours. It is believed that for many applications even superinsulation will allow too much boil-off. Consequently, relique-faction of all or part of the cryogen vapor is being considered as a means of reducing or eliminating boil-off losses. Both closed and open cycle reliquefier systems can offer weight savings and make certain missions possible that previously were not. Furthermore, the reliquefier can be used in conjunction with superinsulation for optimum results.