Heat-Shield Ablation and Sublimation Determinations through Radioisotope Techniques

A technique has been developed for the determination of heat-shield sublimation (char) and surface recession (ablation) during an atmospheric reentry. A radioactive "line" source embedded in the heat-shield material sublimes and ablates at the same rate as the heat shield. Decreases in source activity are monitored by miniaturized nuclear counters. Accuracies exceeding 90 percent are obtainable. The technique provides a continuous indication of char and ablation rates.