Thermal response and surface recession of a carbon-phenolic charring heatshield of spacecraft: Numerical simulation and validation

Abstract

Aero-thermal heating experienced by spacecraft as they enter planetary atmosphere is exorbitant. The response of a sacrificial thermal shielding system of a spacecraft to extreme heating depends on the unsteady dynamics of thermo-physico-chemical interaction of shielding material with high enthalpy plasma. This paper addresses a transient analysis being performed to elucidate these interaction phenomena and to approximate the thermal response and the surface recession of an iso-q model made of low-density, high-porosity carbon/phenolic ablative material. The newly developed finite element material response code of this study solved time-dependent governing equations, including two energy conservation equations (for internal- and surface energy). A three-component chemical decomposition model approximated the material decomposition rate. Darcy's law predicted the direction of pyrolysis gas flow as well as the pressure gradient across the homogeneously porous solid material. A shaver re-meshing technique refined the ablation front posterior to the surface recession. Benchmark solutions were computed and compared against available solutions to interrogate the fidelity of the proposed code. For an identical surface energy boundary condition, the proposed code predicted a material temperature in excellent agreement with the thermal response data inferred from the material response code “Amaryllis”. Besides, the predicted char contours were similar to that of a high enthalpy air-plasma-exposed iso-q specimen. The outcomes of this study will reinforce the confidence of spacecraft engineers on the proposed code for the aero-thermal analysis of next generation sacrificial thermal shielding systems.