Spectral and global emissivity assessment by means of a novel infrared methodology

Abstract

One of the most critical phases for a space mission involving a transportation system from space to Earth is the atmospheric re-entry since the high kinetic energy of orbital flight shall be reduced and converted in thermal energy. In these conditions, one of the design parameters that allow the TPS to withstand the aerothermal loads and to guarantee temperatures compatible with the selected materials is the emissivity. This parameter depends on several factors such as mechanical features, chemical composition, surface roughness, angle of sight, wavelength and temperature. For TPS materials, emissivity characteristics are difficult to evaluate due to harsh, and critical to simulate on-ground, operative environment characterized by material surface and plasma flow interaction.

In this work, a novel approach to detect the material spectral emissivity at several wavelengths, ranging from NIR (Near InfraRed) to the LW (Long Wavelength) spectral range, is presented. An experimental set-up composed of a black body, a pyrometer and two thermal cameras has been used for performing an accurate detection of the emissivity value at several wavelengths. The experimental analyses guarantee a systematic approach able to provide quantitative information of the spectral and global materials emissivity.

The ISiComp® material, a long carbon fiber reinforced SiC matrix composite (C/SiC) made in Italy and developed by CIRA and Petroceramics, has been used.