A High Efficiency Cryocooler for In-Space Cryogenic Propellant Storage

NASA is considering multiple missions involving long-term cryogen storage in space. Liquid hydrogen and liquid oxygen are the typical cryogens as they provide the highest specific impulse of practical chemical propellants. These cryogens are stored at temperatures of nominally 20 K for hydrogen and 90 K for oxygen. Due to the large size of these tanks, refrigeration loads to maintain zero-boil-off are high, on the order of 10's of watts at 20 K and 100's of watts at 90 K. Space cryocoolers have been developed for cooling space sensors that have modest cooling loads and are not suitable for high capacity applications. On this program, we propose to develop a high capacity turbo-Brayton cryocooler that provides 150 W of refrigeration at 90 K. On the Phase I project, we will design the cryocooler, assessing the size, mass, and performance, and assess development risks. On the Phase II project, we will develop and demonstrate a critical cryocooler component. In Phase III, we will build and demonstrate an engineering model cryocooler. Successful completion of this project fills a clear void in space cryocooler technology.