Spectral Emittance of Ablation Chars, Carbon, and Zirconia to 3700 deg K

Hemispherical Spectral Emittance of Ablation Chars, Carbon, and Zirconia to 3700 deg K
Authors: R. G. Wilson; NATIONAL AERONAUTICS AND SPACE ADMINISTRATION HAMPTON VA LANGLEY RESEARCH CENTER

Abstract: The initial results of the application of special optical techniques to high-temperature emittance and reflectance studies of an ablation-material char and certain other refractory materials representative of those present in ablation residues formed during aerospace reentry operations are presented. Spectral hemispherical emittance and reflectance were determined with an image pyrometer integrated with an arc-imaging furnace for carbon, graphite, zirconia, and a phenolic-nylon ablation-material char at wavelengths from 0.37 micrometer to 0.72 micrometer for temperatures from 2100 deg K to 3700 deg K. The data obtained are compared with those of other investigations to the extent that the existence of comparable data permits. Surface-roughness properties of the materials studied were determined from measurements made with a light-section microscope. The dependence of the spectral hemispherical emittance of oxidized carbon at a wavelength of 0.65 micrometer on its surface-roughness properties was investigated experimentally and the emittance was found to be a linear function of the root-mean-square slope of the surface when the roughness is large compared with wavelength. p3

Limitations: APPROVED FOR PUBLIC RELEASE
Description: Technical note
Pages: 31
Report Date: MAR 65
Report Number: A107703