Qualification of a 90 K high-capacity cryocooler for cryo fluid management

Creare recently completed integration, qualification testing, and delivery of a high-capacity turbo-Brayton cooler designed to meet NASA’s needs for long-duration storage of liquid oxygen and methane in space. High capacity is defined as providing over 100 W of refrigeration at 90 K for the purposes of this paper. Zero-boil-off storage of these propellants is a key enabling technology for several NASA missions. Due to the size of the propellant tanks, an active refrigerator is required to intercept the heat loads, maintaining the cryogen temperature and eliminating boil-off. This cryocooler is a scaled-up version of the 20 W, 90 K cryocooler that Creare delivered to NASA in 2012 which was used in NASA’s initial ground demonstrations of reduced boil-off hydrogen storage and zero-boil-off oxygen storage. The cryocooler was integrated in a flight prototypical arrangement suitable for thermal performance and launch vibration testing and to support planned ground-based zero-boil-off demonstrations at NASA. The demonstrated refrigeration capacity is over 120 W of refrigeration at 90 K and over 200 W at 118 K, supporting a broad range of storage pressures for both liquid oxygen and liquid methane respectively. Launch vibration testing was also successfully completed on the integrated unit. This paper reviews the qualification test results for the cryocooler and presents specific power and specific mass estimates for a flight version of the cooler.