NEW APPROACH TO THE PASSIVE THERMAL CONTROL SYSTEM WITH LOW-TEMPERATURE “AL-NH3” HEAT PIPES: QUALIFICATION TESTING RESULTS AND FLIGHT PERFORMANCE ON MICROSATELLITE BIRD

An important question of exploitation of near-Earth space environment investigation satellites is the support of a thermal regime of satellite as a whole and devices in particular. Guarantee of their reliable working in space depends on thermocontrol system (TCS) operation that is confirmed by qualification working-off ground tests both with heat pipes separately and when they are a part of satellite TCS. The program of qualification tests and its realisation is considered in this paper. The typical modelling object is an ammonia aluminium grooved heat pipe (shell diameter of 12 mm, 30 grooves) developed for DLR's BIRD small satellite program. Qualification tests consist of thermal steady-state and non-stationary performance tests, long life tests, environmental tests and others reviewed in the paper. Tests of determination of thermal resistance, maximum heat transfer rate, influence of tilt on maximum heat transfer rate are related to determination of thermal technical characteristics of heat pipes. Start-up tests, in which an ability of heat pipe to continue the function normally after certain power surge is determined, tests on definition of priming time, in which the priming time of heat pipe capillary structure after its full drainage by method of direct discharging and continuing the power supply is defined, are related to non-stationary tests. During the long life tests an ability of heat pipe to function for a long time is checked and quantity of noncondensable gas generated is defined. Test program was realised on test facilities of the National Technical University of Ukraine “Kyiv Polytechnic Institute” (Kyiv, Ukraine) and Institute of Structural Mechanics (Berlin, Germany). The analysis of heat pipe operation during qualification test and flight performance of BIRD satellite is shortly reviewed on the base of telemetric information