Long-Term Cryogen Storage Technologies for Orbit Transfer Vehicle

The simplicity of a solar thermal propulsion system offers promise of very low cost compared to advanced cryogenic stages for earth orbit missions. Integrated solar thermal propulsion and power technology has evolved significantly over the past two decades through the combined efforts of the Air Force, NASA, and the aerospace industry. This technology is capable of offering 2-10 times the efficiency of existing chemical propulsion systems while simultaneously providing 30-100 kilowatts of electrical power at one-third to one-tenth the cost of advanced photovoltaic systems. The Solar Orbit Transfer Vehicle (SOTV) has been identified as a valuable space-based system for maintaining critical United States space assets. The upper propulsion stage for SOTV involves the storage of liquid hydrogen (LH2) on orbit. In several mission scenarios, the cryogen must be maintained for long periods, approaching up to five years. Key to enabling a stored cryogen system with this capability is the development of an active cooling system that can counteract the thermal loads due to the warm external environment of a low earth orbit. TAI is proposing to develop a hybrid cryocooler with a Brayton-cycle lower stage that is ideally suited for the cryogenic cooling needs of SOTV.