Space Cryogenic Refrigerator System (SCRS) Thermal Performance Test Results

Abstract

The Space Cryogenic Refrigerator System (SCRS) is a Split-Stirling Cryocooler developed by Lockheed and Lucas Aerospace. The cooler uses two 20-mm compressors coupled to two 10-mm displacers via transfer tubes. It is required to produce 2W of thermal cooling at an instrument interface temperature of 65K for less than 100W of input power into the cryocooler’s controller. The controller uses Lockheed’s proprietary Digital Error Correction (DECS) control system to provide cryocooler operation and vibration control.

The cooler was tested in Lockheed’s Cryocooler Thermal Vacuum Chamber by thermally soaking the cooler and electronics to 220K for 48 hours and then warming the system and starting it at 250K. The system was operated at heat rejection temperatures of 250K, 270K, 300K and 320K in a vacuum environment. System power, temperature control, temperature stability, and external cooler and controller temperatures were measured during the testing which was conducted at steady-state conditions for eight hours except for at 300K, which was conducted for over forty-eight hours.

The cooler successfully demonstrated 2W of cooling at 65K with a 300K heat rejection for 125W of total system input power. Although it did not meet the 100W input power requirement, it did show excellent thermal margin at 65K (80% of maximum compressor stroke) and temperature control and stability.