Application of the Turbo-Refrigerator to Long-Term Cryogenic Storage

Storage of cryogenic fluids in space for long periods is being considered in some mission plans. Weight penalty due to fluid vent loss can be high when lengthy periods of low usage are desired. Launch weight may be minimized by active refrigeration of the stored cryogen. The turbo-refrigerator is a closed-cycle cryogenic cooler well suited to such applications. Since this approach is based on the use of gas-bearing turbomachinery, life limitation due to wear is virtually absent, making extremely long periods of uninterrupted operation feasible. Long-term storage of hydrogen and oxygen is investigated, showing that, for a one-year mission, refrigerated storage results in lower weight for usable liquid hydrogen quantities above 3500 lb; liquid oxygen storage penalties are less, irrespective of the quantity, at this mission duration.