Measurement of Thermo-Radiation Characteristics of Spectral-Selective Materials for Space Structures Designs

The aim of the work is to demonstrate the perspective of calorimetric measurements of thermo-radiation characteristics without vacuuming the volume of the measuring chamber, substantiating the structure and characteristics of the equipment for these studies, carrying out an experimental verification of the method and equipment on the real samples of materials for space technology.

The possibility of using the calorimetric method for measuring the emission factor without vacuuming the volume of the measuring chamber, taking into account the heat transfer from the radiator to the surface of the sample through the air layer, is substantiated. The structure of the corresponding apparatus is recommended and the ratio of the geometric dimensions of the working chamber, in which the boundary distortion due to heat transfer through the air is insignificant, and the correction for conductive heat exchange can be easily calculated, is defined. The method of measurement and the description of the test stand on the basis of thermoelectric heat exchangers and absolute solar radiation receiver, which are intended to determine the absorption coefficient of solar radiation, are given.

A brief description of the technology of coating Al+TiO2 layered structure and the measured values of emission factor and absorption coefficient of samples with such coating is given. It is shown that the ratio of the absorption coefficient of solar radiation to the emission factor for a two-layer coating is significantly lower than the similar value obtained for its individual components. It is established that by changing the ratio of thickness of layers of Al and TiO2 it is possible to reduce the ratio of coefficients to the value that provides an acceptable level of temperature of the surface of the spacecraft.