Demonstration of a TwoStage Turbo-Brayton Cryocooler for Space Applications,” Cryocoolers 15

Turbo-Brayton cryocoolers have inherent technical advantages for many space applications because of their extremely low emitted vibration and simplicity of integration with payloads and spacecraft heat rejection systems. The technology was demonstrated in space in March 2002 when the NICMOS Cryocooler was installed on the Hubble Space Telescope. The NICMOS Cryocooler is a single-stage unit that supplies 7 W of refrigeration at 70 K and has exceeded six years of space operations without degradation or malfunction. More recently, the need for efficient cooling at multiple temperatures has driven the development of a two-stage turbo-Brayton cryocooler. An initial brassboard two-stage cryocooler was built and tested. This unit relies heavily on NICMOS technologies for the mechanical hardware, but uses new control electronics that have been designed for precise and independent control of two load temperatures. The cryocooler was optimized to simultaneously provide at least 1.8 W of refrigeration at 65 K and 12.6 W of refrigeration at 100 K, and the mechanical hardware weighs approximately 21 kg. The unit underwent extensive thermal vacuum testing to demonstrate thermodynamic performance and flight-like operations. This paper describes the design features and performance of the cryocooler