Spectral emissivity of metals after damage by particle impact

The reflectance, R, solar absorption, alpha, thermal emittance epsilon, and the alpha/epsilon ratio were determined for several metals before and after bombardment by high velocity microprojectiles. Observed decreases of 1 to 26 percent in the reflectance of various metals were apparently dependent on the amount of surface area damaged as well as on the velocity of the impinging projectiles. The thermal emittance was observed to increase more than the solar absorptance, which resulted in a net decrease in the alpha/epsilon ratio in all metals investigated except stainless steel 304. In the case of stainless steel 304, alpha and epsilon were observed to increase equally, resulting in an alpha/epsilon ratio apparently insensitive to microprojectile bombardment. Recommendations for the continuation of these investigations are outlined.