Flight Results from the Cryogenic Thermal Storage Unit (CTSU) Flight Experiment on STS-95

This paper describes the Cryogenic Thermal Storage Unit (CTSU) flight experiment, which flew as part of the CRYOTSU payload on STS-95 in late 1998. The CTSU flight unit is a dual-volume nitrogen triple-point device with a 140 cc beryllium cryogenic heat exchanger and a 17 liter stainless steel ambient storage tank. During the 9-day flight, the CTSU completed all testing goals including 22 full freeze-thaw and 18 partial freeze-thaw cycles at power levels from 5-9 W. All tests were successful and demonstrated 3000 J of energy storage at 63.15 K. An additional test was performed which demonstrated nitrogen’s solid-solid transition at 35 K with 1000 J of energy storage. The zero-g environment had no discernible impact on CTSU operation.