Sumitaka Tachikawa

Abstract In this study, thermal effusivity distributions of two polished JSC-1A particles, a lunar regolith-simulating material, were measured using a thermal microscope. The results confirmed that the average thermal effusivity of the JSC-1A single particle was approximately half that of the FJS-1 single particle, a different type of lunar regolith-simulating material measured by a similar method. Also, the thermal effusivities of the existing mineral phases of pyroxene and anorthite in the particles were obtained and were comparable to those reported in the literature. A possible reason for the lower thermal conductivity of JSC-1A than that of FJS-1 could be the differences in the ratio of the mineral phases, and phase boundaries between the mineral phases.

Abstract In recent planetary exploration space missions, spacecraft are exposed to severe thermal environments that are sometimes more extreme than those experienced in earth orbits. The development of advanced thermal control materials and devices together with reliable and accurate measurements of their thermophysical properties are needed for the development of systems designed to meet the engineering challenges associated with these space missions. We provide a comprehensive review of the state-of-the-art advanced passive thermal control materials and devices that are available for space applications, specifically, variable emissivity thermal control materials and microelectromechanical systems (MEMS), radiofrequency (RF)-transparent and/or tunable solar absorptivity and total hemispherical emissivity thermal control materials, and a passive re-deployable radiator with advanced materials and insulation. Prior to our in-depth review of these thermal control materials, we briefly summarize the thermal environments surrounding spacecraft, the characteristics of thermophysical properties for spacecraft materials that differ from those of materials for ground use, and the significance of solar absorptivity and total hemispherical emissivity for passive thermal control in space. In all four topics of materials and devices, the following subjects are overviewed: the basic principle of passive thermal control techniques in space, the measurement of thermophysical properties of those novel materials, simulation and/or on-orbit verification thermal performance tests, degradation tests in space environments, and some aspects of the implementation of the above-described materials and devices in actual space missions.