No abstract

This study proposes a passively deployed radiator as a new thermal control device for small satellites. This radiator can control the amount of heat dissipation by varying the heat rejection area, depending on its temperature. This radiator consists of a fin, a baseplate, and an actuator. First, thermal diffusivity, total hemispherical emissivity and solar absorptance of graphite sheets, which is a part of this radiator fin, were measured. From these measurements, thermal conductivity of the graphite sheet varies from 950 to 1490W/mK, the total hemispherical emissivity is from 0.22 to 0.31, and the solar absorptance is 0.66. Second, the performance of the radiator was calculated by thermal analysis as a function of size and thickness, and the 1/2 scaled test model of this radiator was designed. Third, the test model was fabricated and thermal performance was tested in a vacuum condition. The testing showed that the thermal dissipation of this 1/2 scaled radiator is 54W at 60℃, the fin efficiency difference between deployed and stowed position is 0.35, and the specific heat rejection is 188W/kg, respectively. NomenclatureA MLI = Fin area of MLI side A e = Surface area of a sample = Absolute spectral absorption rate A rad = Fin area of radiation side c p = Specific heat D = Thermal diffusivity d = Thickness = Thermal diffusivity in the in-plane direction = Thermal diffusivity in the thickness direction εeff(MLI) = Effective emissivity of MLI 2 εH(rad) = Total hemispherical emissivity of radiator side f = Frequency = Constant η = Fin efficiency J = Spectral solar radiation energy l = The thermal diffusion length L = The distance from the end of the sample to the heating point PSL-2KPH = Thermostatic chamber = Amount of heat loss = Quantity of heat = Total quantity of heat dissipation from a radiator = Thermal conductivity = Density = Absolute spectral reflectance of the reference = Absolute spectral reflectance of the sample = Relative spectral reflectance of the sample = Stefan-Boltzmann constant SMA = Shape memory alloy SRS99 = The reference sample of reflective plate T ac = AC temperature T e = Temperature of the sample T h = Temperature of heat source T s = Temperature of surroundings w = Width