A Thermal Storage Unit For Low Temperature Cryocoolers

Abstract

The Air Force has developed a lOK Cryocooler based on a hybrid approach of combining different cooling technologies into a single cryocooler. The Air Force Hybrid lOK Cryocooler combines a Stirling cryocooler as a precooler and a Joule-Thomson cooling stage to create a cryocooler that produces cooling at lOK. Redstone Aerospace has completed a Small Business Innovation Research contract to develop a unique thermal storage unit (TSU) for the AFRL lOK cryocooler. The purpose of the development was to demonstrate an effective method of substantially increasing the cryocooler's peak cooling capacity for short periods of time. This would enable a cryocooler sized for the average load to meet the needs of future missions, thereby reducing the overall size, weight and input power of the cryocooler. This new TSU technology allows the AFRL 1 OK Cryocooler, which is based on the Redstone Interface concept, to maintain the sensor temperature at precisely lOK in the presence of a widely varying load. In addition, analysis has shown that this TSU technology can be effectively applied to systems down to 4K. Testing has demonstrated that the TSU is highly effective in increasing both the magnitude and duration of the AFRL 1 OK Cryocooler's peak cooling capacity. The peak cooling capacity at lOK increased in both magnitude and duration. This paper describes the cryocooler and presents the test results.