For the info of WideBodiedEng and any others who may have not followed the investigation in depth, the Shuttle stack was accelerating through about Mach 2.6 at the time the foam segment detached. Its impact speed at the leading edge was accurately determined from high-speed film to be around 500 mph. Both the released videos of the event clearly show that the impact was forceful.
Also, do not confuse tiles with RCC sections and tank foam. Tiles are not at issue in this accident.