Accession Number : ADA307326

Title :   Thermal Performance of 625-kg/m3 Elastomeric Ablative Materials on Spherically Blunted 0.44-Radian Cones.

Descriptive Note : Technical memo,

Corporate Author : NATIONAL AERONAUTICS AND SPACE ADMINISTRATION HAMPTON VA LANGLEY RESEARCH CEN TER

Personal Author(s) : Chapman, Andrew J.

PDF Url : ADA307326

Report Date : NOV 1972

Pagination or Media Count : 55

Abstract : Spherically blunted 0.44-radian (25 deg) half-angle conical models coated with elastomeric ablative materials were tested in supersonic arc-heated wind tunnels to evaluate performance of the ablators over a range of conditions typical of lifting entry. Four test conditions were combinations of stagnation-point heat-transfer rates of 2.3 and 4.5 MW/m2 (200 and 400 Btu/ft2-sec) and stagnation pressures of 20 and 2 kN/m2 (0.2 and 0.02 atm). Afterbody values of heat-transfer rate and pressure were 0.05 to 0.20 of stagnation-point values. Stagnation enthalpy varied from 4.4 to 25 MJ/kg (1900 to 11 000 Btu/lbm) and free-stream Mach number was in a range from 3.5 to 4. Ablative materials retained the spherical nose shape throughout tests at the lower heat-transfer level, but receded, assuming a flattened nose shape, during tests at the high heat-transfer level. The residue layer that formed on the conical afterbody was weak, friable, and extensively cracked. The reference ablative material, which contained phenolic microspheres, generally retained the conical shape on the model afterbody. However, a modified ablator, in which phenolic microspheres were replaced with silica microspheres, deformed and separated from the undegraded material, and thereby produced a very uneven surface. Substrate temperatures and ablator recession were in good agreement with values computed by a numerical analysis, for which one set of material properties and environmental data represented the four test conditions.

Descriptors :   *THERMAL ANALYSIS, *ABLATIVE MATERIALS, HEAT TRANSFER, ABLATION, SLENDER BODIES, ATMOSPHERE ENTRY, PERFORMANCE(ENGINEERING), SILICON DIOXIDE, DEFORMATION, ELASTOMERS, THERMAL STABILITY, TEMPERATURE GRADIENTS, SPACE SHUTTLES, WIND TUNNEL TESTS, PROTECTIVE COATINGS, HEAT SHIELDS, LEADING EDGES, MACH NUMBER, LIFTING REENTRY VEHICLES, FREE STREAM, SURFACE TEMPERATURE, ENTHALPY, CONICAL BODIES, AERODYNAMIC HEATING, THERMAL DEGRADATION, BLUNT BODIES, SUPERSONIC WIND TUNNELS, STAGNATION PRESSURE, STAGNATION POINT, AFTERBODIES, MICROSPHERES.

Subject Categories : Thermodynamics
      Elastomers and Rubber
      Spacecraft Trajectories and Reentry

Distribution Statement : APPROVED FOR PUBLIC RELEASE