Technical Paper
Investigation of Radiant Characteristics of Thermal Protection Materials and Coatings in Simulated Exploitation Conditions
1999-07-12
1999-01-2088
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.
