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The Heat Rejection Subsystem is designed to provide the waste heat rejection for the Active Thermal Control System of the International Space Station Alpha. The design consists of six deployed radiator arrays, each identical, interchangeable and orbital replaceable, which provide the 70 kW heat rejection needs of the two Active Thermal Control System liquid anhydrous ammonia heat transport loops. The radiators are unlatched and deployed remotely without EVA after their carrier structural segment is assembled to the space station in orbit. The radiators are designed to meet the near earth orbit space environments for a 10 year period. These environments include micrometeoroid, space debris and solar energy radiation which degrade materials' and extreme thermal environmental temperatures which can be low enough to freeze the ammonia working fluid. The radiator is designed to be stowed for launch on the Space Shuttle while attached to the mating Space Station segments.

A connectable/disconectable thermal interface has been developed for the constructable radiator system under development at NASA-Johnson Space Center. A contact heat exchanger approach which involves pressurized clamping of a segmented cylindrical heat exchanger on the outside of a round heat pipe evaporator section was designed, fabricated, and tested. Dry metal-to-metal contact conductance heat transfer is utilized. Test results have indicated excellent contact conductances of up to 8500 w/m2°c (1500 Btu/ft2°F) at 2000 kPa (300 psi) clamping force. The feasibility and fabricability of the design have been demonstrated.