Measurement of the complex refractive index and complex dielectric permittivity of T.P.S. Space Shuttle tile materials at millimeter wavelengths

Complex refractive index and dielectric permittivity studies of presently used Space Shuttle tile materials at millimeter wavelengths reveal these tiles to exhibit similar absorption characteristics to those of fused silica materials. This absorption is mainly related to the water content in the specimen. A strong birefringence is observed at least in one of these fibrous refractory composite materials.