Thermophysical Properties of High-Thermal-Conductivity Graphite Sheets for Spacecraft Thermal Design

Thermophysical properties of a new material - a graphite sheet, which has characteristics of high thermal conductivity, anisotropy, lightweight and flexibility - have been measured in order to apply this sheet to a spacecraft thermal control material. The following measurements were performed: 1) The thermal diffusivities in the in-plane and out-of-plane directions were measured over the temperature range from 100 to 350 K using a laser heating ac calorimetric method. 2) The specific heat and the total hemispherical emittance were measured over the temperature range from 173 to 375 K using a transient calorimetric method. 3) The solar absorptance was measured using a spectroscopic method for angles of incidence ranging from 5 to 60 deg. Additionally, the thermal conductivities and the specific thermal conductivities were calculated using the measured results, and the high potential of this graphite sheet as a material for spacecraft thermal control was confirmed.