The Trail to the Leading Edge

This article focuses on SwRI that had conducted impact experiments, experiments of the sort that would be needed now, on the orbiter's thermal protection system. Studies had included the effects of foam insulation, ablator, and ice striking both carbon-carbon materials similar to those that line the shuttle's leading edges and the silica thermal protective tiles that cover most of the rest of the craft. Concurrently, SwRI developed detailed analytic and numerical models of foam insulation's impact on thermal tiles. The models provided a curve for distinguishing between damage and no damage, based on speed and impact angles. Given an impact speed and angle for an incoming piece of foam insulation, the model determined whether or not tile material would sustain damage. The SwRI model agreed extremely well with previous tile impact tests and would agree with the five tests performed during the Columbia accident investigation of foam insulation impacting tiles.