Preliminary Thermal Design of UNITEC-1

UNITEC-1 is a nano-spacecraft that flies to Venus. The preliminary thermal design of UNITEC-1 has been carried out. It has been clear from 1 node analysis that slow tumbling of the rotation axis is effective to reduce the temperature variations. It is difficult that both temperatures of the worst-case cold condition and the worst-case hot condition are within the allowable temperature ranges. It is desirable to conduct the survival competition as soon as possible after UNITEC-1 separates from a rocket. It is recommended from this viewpoint to use the black Kapton on the external surface except solar cells. It is clarified from the multi nodes analyses using Thermal Desktop/ SINDA/FLUINT that the temperature of the transmitter changes from 14.8 to 21.0 degree Celsius in an operational sequence under the worst-case cold condition. The temperature change of the battery can be suppressed from 15.5 to 16.6 degree Celsius in an operational sequence under the worst-case cold condition using the insulator between the battery and the internal surface. The maximum difference of temperature occurs between UOBC3 and UOBC6, and is 2.8 K. This difference is enough small to conduct the survival competition under the equal condition. The minimum period for the mission is about 114 days after UNITEC-1 separates from a rocket.