Thermal Design of Upper Boost Stage with Hybrid Kick Motor for Microspacecraft
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This paper proposes thermal design of the upper boost stage with a hybrid kick motor for increasing the deep space exploration from a geostationary transfer orbit by microspacraft. The oxidizer of the hybrid kick motor is nitrous oxide. The main challenge in this paper is to keep the temperature of the nitrous oxide below 35 degree Celsius to keep the nitrous oxide in a liquid condition before the ignition of the hybrid kick motor. The upper temperature limit is lower than that of the allowable temperature range of many on-board devices. The sunshine and shade time per orbit on the orbit are longer than those on low earth orbits and the temperature fluctuates violently in an orbit. The shape of the upper boost stage is 50 cm cubic. Solar cells are body-mounted and the passive thermal control is based. Two thermal design strategies are applied: Design concept A reduces temperature change in an orbit by using the heat capacity of the entire spacecraft. Design concept B reduces the temperature change in internal structures by transferring the little external heat to the internal structure. Assuming the thermally worst attitude of the upper boost stage, no design solution is found. The design solution is found from design concept B under the attitude condition of the normal flight, in which the upper boost stage rotates about the hybrid kick motor axis.