Design and analysis of micro thermal switch using the near-field effect for space applications

With space developments for diversified missions, intelligent thermal design of spacecraft is essential. This report proposes an active thermal radiation control device, which consists of an array of thermal switch that is enhanced by the near-field radiation. Suspended diaphragms are snapped down by electrostatic force, when the driving voltage is applied to the top electrode. The present simulation for parallel plates of Au (lower electrode) and Cu (upper electrode) at 300 K shows that the effective emittance of 0.02 for a 1 μm separation is dramatically increased to 0.89 for a 10 nm gap. A MEMS (Micro Electro Mechanical Systems)-based active radiator was designed based on the requirements for the driving voltage and resonant frequency. The fill factor of the proposed radiator is as large as 61%. In this study, an analysis based on thermal resistance of various heat paths was conducted. It was found that the thermal resistance of the near-field effect was lower than that of contact heat conduction, indicating that the ON-OFF switching performance is largely improved by near-field radiation. The heat flux in the ON state can be enhanced by a factor of 28.5 (T1 = 400 K, T3 = 3 K).