Space helium refrigerator

The description, main characteristics and flight tests results of the closed-cycles three-cascade helium refrigerator operating to 4.4 K are presented. The refrigerator is intended for the cooling far-infrared (submillimeter) detectors of the telescope BST-IM on board of the orbital station ‘Salyut-6’. The cryogenic system which uses two high efficient gas cooling machines operating under Sterling cycle for the preliminary cooling at levels 80 K and 20 K and Joule-Thomson cooling effect to obtain the temperature 4.4 K, is compact and simple to operate in automatic regime. The first space helium refrigerator described provides the useful refrigeration of 0.5 W with power requirements of less than 1.5 kW. According to the data obtained during more than two years flight tests on board of ‘Salyut-6’, all the refrigerator's systems operate within the limits of standards and provide the reliable cooling of the telescope's detectors.