Storage and utilization of liquid hydrogen on board the Pegase

Results of a study of a cryogenic tank on board the Pegase platform are presented. A volume of 860 cu m of liquid hydrogen necessary for the duration of a year's mission, is contained in one or three spherical reservoirs. The thermal insulation is obtained by superinsulators in a vacuum container, and the daily losses are 0.7%. The internal sphere, a light alloy (AZ56) or containing titanium, has a minimum weight of approximately 5 tons. The use of honey-combed material allows significant weight gain for the external sphere. The total weight of the reservoir is about 15 tons (structure index 0.25). Interest in the recondensation of hydrogen vapors and the utilization of mixed liquids-solids (slush) is evaluated. The vaporization and reheating of hydrogen are done in a freon exchanger permitting the energy recovery necessary for cooling the compressed air for the combustion cells.