Compatibility of dielectric and heat shield material combinations during ablations

The surface recession and mass-transfer rates of materials suitable for reentry thermal protection of microwave antennas have been examined. Experiments were performed with subsonic-turbulent flow of air in a confined channel. In supporting experiments, selected material combinations were subjected to ablative splash tests in the Sandia High Enthalpy Arc Tunnel. Microwave window materials were tested adjacent to ablative heat shield materials in combinations and configurations under consideration for reentry vehicle applications. Test results indicated that fused silica was compatible with quartz-phenolic and carbon-phenolic heat shield materials while the ablative characteristics of hot-pressed boron nitride were very similar to those of the STC-7 carbon composite developed by Sandia Laboratories. (U.S.)