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Some methods and facilities for the measurement of thermo-optical properties as total hemispherical and normal emissivity as well as directional emissivity and directional solar absorptivity are presented. Total hemispherical and normal emissivity result from the measurement of the heat flux radiated from the surface of a sample, which rotates in a isothermal heating zone of controllable temperature. This method is realized for emissivity measurements on e. g. spacecraft and thermal protection materials in the temperature range 150 K ≤ T ≤ 2000 K under vacuum conditions and at adjustable air pressures simulating typical exploitation conditions. This method and the corresponding facility have been modified for the evaluation of directional emis-sivities of materials and coatings. Inserting diaphragms of adapted apertures between radiating surface and detector enables the measurement of the axis-symmetric radiation heat fluxes under certain angles.

Multi-layer insulations consisting of stacks of reflecting foils reveal extremely low thermal conductances under vacuum conditions. Therefore, to improve the thermal performance of a pure foam and to reduce the area related mass, experimental and analytical investigations have been extended to a combined advanced multi-layer/foam insulation concept which consists of a stack of reflecting screens separated by thin foam layers. The predicted thermal performance of this improved insulation concept is compared with test results.

A Flexible External Insulation (FEI) is being developed for the thermal protection of spaceplanes and re-entry capsules. Presently, forward extension of the FEI to locations of higher aerothermal loads is being studied. To evaluate the FEI under simulated re-entry conditions a test campaign has been planned and performed by the Rarefied Gas Dynamics Laboratory of the Russian Central Aerohydrodynamic Institute (TsAGI). Coated and non-coated FEI fabrics were exposed to a hypersonic high-enthalpy air flow in the VAT-104 plasma wind tunnel.