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The thermo-optical properties of thermal protection systems for spaceplanes or capsules mainly govern the temperature of the aerothermally heated outer surface during ascent and re-entry. High emissivities are favourable to achieve significant surface temperature reduction. Adding of filler materials to a coating is a potential method to improve the emissivity at higher temperatures. When the refraction index of the coating material varies only slightly with temperature, it is demonstrated that overlapping of the spectral emissivities determined at RT with the Planckian spectrum at temperatures T predicts the temperature behaviour of the coating emissivity within a technically acceptable uncertainly bandwidth.

In the frame of the ESA “Manned Space Transportation Programme” (MSTP) the applicability of flexible insulation blankets as thermal protection system of the conical surface of capsules is investigated. The blankets have to withstand the severe ascent and re-entry aerothermal and aerodynamical environment at temperatures of up to 1200 °C. For this temperature regime ceramic components are to be applied due to their excellent temperature stability and strength properties. In the frame of a comprehensive thermal and structural characterization of these materials thermal conductance measurements are performed on a ceramic fibrous core material and a blanket in this operational temperature range at gas pressures ranging from near vacuum up to ambient conditions.