Impact damage characteristics of Space Shuttle Orbiter thermal protection tiles

Abstract

Space Shuttle Orbiter thermal protection tiles were subjected to impacts under various conditions, ranging from low-velocity impacts with a large, high-mass object to high-velocity impacts with a small, low-mass projectile. Fractography showed that failure of the glaze was due to bending (with the origin at the glaze/tile interface), or impact (with the origin on the surface being struck), or a combination of these two. Tiles made using experimental compositions of fibrous refractory composite insulation were more resistant to impact damage than those made from vitreous silica fibers only. The primary reason for this difference was the fact that the glaze was in compression on the experimental tiles, while it was in tension on the standard tiles. Impacts with large objects tended to produce bending failures, offen with extensive surface cracking. Impacts with small projectiles, especially when at higher velocities, tended to produce impact or mixed bending/impact failures; damage was localized, with holes offen being punched in the coating.