Thermal management of space-based, high-power solid-state RF amplifiers. Final report

The advanced weapons concepts envisioned by the SDIO employed a wide array of highly energetic devices, which due to inefficiencies, generate large quantities of waste heat. Power and thermal management are integrally related. In the vacuum of space, disposing of waste energy is a major problem which can contribute as much as 50% to the overall spacecraft mass and volume. The problem becomes more acute as the temperature at which the energy must be rejected is lowered. In an earlier study, thermal management issues associated with megawatt class RF microwave tubes were explored to determine if there were simple, approximately mass neutral schemes which might be adapted to dispose of the waste energy generated within a tube collector operating in space. The assumptions for that study were: (1) Tubes were in the megawatt class-70% efficient for single simple collector and 90% efficient for depressed collectors, (2) On-board, super critical hydrogen was available at a pressure of 35 bars and a temperature of 35 K. (3) The largest single event run time was 500 seconds. (4) The device would be dormant for long periods of time, be required to become active in tens of seconds followed by long periods of dormancy. (5) The only allowable effluent is hydrogen. (6) System impact must be minimal