THERMAL DESIGN FOR THE CYCLIC WORKING COMPONENT IN SPACECRAFT USING THE SOLID THERMAL BUFFER MASS AS A THERMAL CAPACITOR

摘要

Some electrical components in spacecraft operate in cyclic manner. The duty phase of the components isgenerally short compared to the whole period of the cycle. The component heats up with operation and itstemperature hits the highest peak at the end of the duty phase due to the heat dissipation. During the off-duty phasethe component temperature continues to fall until the next sortie. There are the required temperature limits in thecomponent thermal design. Because the highest temperature should not exceed the maximum limit the radiator isdesigned its size to emit enough heat into the space. When the cooling down temperature reaches the minimum limitthe extra heater power is required to compensate the energy loss from the radiator. Although the high heat dissipatingcomponent working in short duty the radiator should be designed for the peak temperature and then it leads the oversizedarea. It affects not only the system size, mass and cost by itself but also the spacecraft power system due to theheater power increment. To reduce the impact on the system design the solid thermal buffer mass (TBM) as athermal capacitance installed between the component and the radiator is a good recommendation. The TBMaccumulates the instantly generated heat and releases the thermal energy moderately, and it makes the time varyingtemperature profile damped down. In this study the mass or thermal capacity of the TBM is optimized to meet thedesign temperature limits of the component based on the mathematical analysis. The linear approximation method issuggested to solve the nonlinear unsteady energy equations caused by 4th order radiation term. As a result thecompensation heater duty cycle lessens compared to original design without TBM.