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The European Space Agency ESA is preparing a mission to planet Mercury called BepiColombo in cooperation with ISAS, the Japanese space agency. Advanced thermal control materials and components are under development to allow the performance of the mission. The present paper gives an overview of the BepiColombo thermal control design and give emphasis to the continued effort in the development of a Solar Reflector Coating (SRC), an Optical Solar Reflector (OSR) and an Infra-Red Rejection Device (IRRD). Key issue in the development and validation of the components and related technologies is the long-term stability under the high temperature and high intensity radiation environment in the vicinity of Mercury. Therefore thermal and radiation endurance testing plays a major role. Candidate materials have been selected and the component design been defined. Development tests will establish mechanical, thermal and optical properties for the initial and end of life conditions.

22 Flexible External Insulation (FEI) Blankets of various types were subjected to a plasma aging in simulated reentry conditions in TsAGI’s VAT-104 windtunnel in the frame of 4 test campaigns on FEI characterization. Blankets were tested at top side temperature Tw =800…1200°C during 60 min each. Widespread numerical simulation of the test conditions and the model heating was performed using full Navier-Stokes equations. FEI catalyticity obtained from correlation between measured and calculated heat fluxes is Kw=1…10m/s.

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.

The flexible external insulation is part of the HERMES thermal protection system. It is designed to cover the central and upper fuselage and upper wing sections. In the central fuselage area, extreme temperatures up to 800°C can be expected. The FEI configuration chosen is described with respect to thermal properties. The thermal development of the FEI is performed in iterative steps of analytical evaluations, experimental investigations and adaptation/improvement of the analytical approach to the test results. During the pre-development work, a two-dimensional thermal mathematical SINDA model of the FEI has been established with separate functions describing radiative, gas and solid heat exchange. The results of transient analyses with respect to external heat loads during re-entry are presented. Calorimetric tests have been performed measuring the heat transfer fractions separately. Test and analysis results are in good agreement.