DEGRADATION AND REUSE OF RADIATIVE THERMAL-PROTECTION-SYSTEM MATERIALS FOR THE SPACE SHUTTLE

摘要

Three silicide-coated columbium alloys and two cobalt alloys were subjected to' identical simulated reentry profiling exposures in both "static" (controlled vacuum leak) and "dynamic" (hypersonic plasma shear) environments.nPrimary emphasis in the columbium-alloy evaluation was on the Cb7 52 and C129Y alloys with a lesser amount on FS85. Commercial silicide coatings of the R512E and. VH109 formulations were used. The coated specimens were intentionally defected to provide the types of coating flaws that are expected in service. Temperatures were profiled up to peak temperatures of either 2350 F or 2500 F for 15 minutes in each cycle.nIn the dynamic cycling, pressure at the specimen surface was on the order of 10 to 25 torr, free-stream velocity was Mach 4 to 5, and aerodynamic shear levels were of-the order of 2 psf.