Accession Number : ADA305295

Title :   Graphite and Ablative Material Response to CO2-Laser, Carbon-Arc, and Xenon-Arc Radiation.

Descriptive Note : Technical note,

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

Personal Author(s) : Brewer, William D.

PDF Url : ADA305295

Report Date : SEP 1976

Pagination or Media Count : 38

Abstract : This study investigated the behavior of graphite and several charring ablators in a variety of high-radiative heat-flux environments. A commercial-grade graphite and nine state-of-the-art charring ablators were subjected to various radiative environments produced by a CO2 laser and a carbon arc. Graphite was also tested in xenon-arc radiation. Heat-flux levels ranged from 10 to 47 Mw/m2. Tests were conducted in air, nitrogen, helium, and a CO2-N2 mixture which simulated the Venus atmosphere. The experimental results were compared with theoretical results obtained with a one-dimensional charring ablator analysis and a two-dimensional subliming-ablator analysis. Neither the graphite nor the charring ablators showed significant differences in appearance or micro structure after testing in the different radiative environments. The performance of phenolic nylon and graphite was predicted satisfactorily with existing analyses and published material- property data. Good agreement between experimental and analytical results was obtained by using sublimation parameters from a chemical nonequilibrium analysis of graphite sublimation. Some charring ablators performed reasonably well and could withstand radiative fluxes of the level encountered in certain planetary entries. Other materials showed excessive surface recession and/or large amounts of cracking and spalling, and appear to be unsuitable for severe radiative environments.

Descriptors :   *ABLATION, *GRAPHITE, *EPOXY COMPOSITES, *THERMAL RADIATION, SURFACE ANALYSIS, MICROSTRUCTURE, ATMOSPHERE ENTRY, HIGH TEMPERATURE, CRACKING(FRACTURING), NYLON, ELASTOMERS, RADIATIVE TRANSFER, NITROGEN, CARBON CARBON COMPOSITES, THERMAL ANALYSIS, THERMAL EXPANSION, SUBLIMATION, HEAT SHIELDS, HELIUM, CONVECTION(HEAT TRANSFER), HEAT FLUX, GRAPHITED MATERIALS, SURFACE TEMPERATURE, WEIGHT REDUCTION, CARBON DIOXIDE LASERS, RADIATION EFFECTS, STAGNATION POINT, ABLATIVE MATERIALS, PHENOLIC PLASTICS, CHARRING.

Subject Categories : Laminates and Composite Materials
      Thermodynamics

Distribution Statement : APPROVED FOR PUBLIC RELEASE