Development of a 5-watt 70 K passive radiator

Abstract

Future space based, infrared, Earth surveillance systems may one day be cooled by large heat pipe radiators operating at 70 K or even as low as 40 K. The use of passive radiators could eliminate the need for mechanical refrigerators and the attendant problems of power consumption and long life reliability. A large two-stage heat pipe radiator was developed for testing on the ground to verify the thermal performance and structural integrity of large, multiwatt, passive cryogenic radiators. The Radiator has a projected base area of 8.1 m^ and is designed to reject a 5 W heat load to space at 70 K. The radiator design includes three oxygen heat pipes which transport the 5 W heat load from a simulated detector focal plane and distribute it over the second-stage radiator surface. The radiator is also designed to withstand the launch environment imposed by a Shuttle orbiter or a Titan III launch. Design tradeoffs are discussed, and the final radiator design configuration is described. Thermal vacuum test results and thermal model predictions are presented. Agreement is very good. Subsequent acoustic testing of the cryogenic radiator test unit and thermal vacuum tests with a 5.1 m2 third stage added are also discussed.