High-capacity turbo-Brayton cryocoolers for space applications

Long-life, high-capacity cryocoolers may be needed for future space systems utilizing stored cryogens. The cooling requirements for planetary and extraterrestrial exploration missions, extended-life orbital transfer vehicles, and space depots may range from 10 W to 50 W at temperatures between 20 K and 120 K. Turbo-Brayton cryocoolers are ideal for these systems because they are lightweight, compact and very efficient at high cooling loads due to the high power density of rotary machines. These benefits are in addition to their inherent attributes of high reliability; negligible vibration; long, maintenance-free lifetimes; flexibility in integrating with spacecraft systems; and ability to directly cool remote and distributed loads. To date, space-borne turbo-Brayton technology has been developed for low cooling loads. The first space implementation of a turbo-Brayton cryocooler was in the NICMOS Cooling System (NCS). The NCS has been operational on the Hubble Space Telescope for over 3.5 years without any degradation. It provides 7 W of cooling at 70 K. The scaling of the technology to higher capacities is the subject of this paper.