Performance of Several Ablation Materials Exposed to Low Convective Heating Rates in an Arc-Jet Stream.

摘要

An investigation was made of the performance of eleven different types of ablation materials bonded to beryllium or aluminum backup plates. Thirty-four specimens fabricated as flat square sections with a nominal side dimension of 5 inches (12.70 cm) were exposed to convective heating rates of less than 10 Btu/(sq ft)(sec) (0.ll4 MW/sq m) for exposure times in excess of 200 seconds in the 2500-kilowatt arc jet at the Langley Research Center. Some of the specimens were tested in air and others, in a mixture of air and nitrogen. The back surface temperature response, the mass distribution loss of ablation materials, and the depth of thermal degradation are presented. The performance of each material during testing is also discussed. A comparison of measured and calculated back surface temperature responses is presented for some of the ablation materials tested in the arc jet. Calculations were made for those materials for which data concerning physical and thermal properties were available. Reasonable agreement was obtained between experimental and calculated temperature responses. Photographs of ablation materials which experienced reentry on the afterbody of the spacecraft of the Project Mercury mission MA-8 are shown. A comparison is made of the physical appearance of identical materials tested in flight and in the arc jet. This comparison indicates that, despite the more severe oxidation in the arc jet stream, certain materials developed the same type of physical defects in both the reentry and arc jet environments.