Effects of finite sublimation rate of carbon graphite on stagnation heating

Reacting stagnation point boundary layers were analytically modeled for sublimation assumptions of the boundary conditions. The study was conducted to upgrade predictions of the aerothermal heating environment that will be experienced by a Jovian probe with a carbon ablative shield. The effect of finite rate sublimation was examined using the Knudsen-Langmuir equations with specified sublimation coefficients in the surface boundary conditions. The flow was assumed axisymmetric, steady, laminar, viscous, and compressible, and the atmosphere was assumed to be a hydrogen/helium mixture. Exact solutions were obtained for the boundary layer equations for both sublimation assumptions. The results suggest that the mass loss rate of equilibrium flow with the equilibrium assumption is significantly larger than found with the finite rate assumption. Carbon heating rates are not affected by the sublimation rate law and are affected by the chemical reactions, especially hydrogen dissociation-recombination in the gas phase.