Low-density ablator response to induction plasmatron aerothermal environments

The aerothermal response of low-density charring ablators for atmospheric entry is investigated in dissociated air and nitrogen plasmas. NASA’s Phenolic Impregnated Carbon Ablator, and its carbon preform, FiberForm, were subjected to aerothermal environments relevant to Earth and Titan atmospheric entry in the Plasmatron X inductively coupled plasma wind tunnel. The response of these materials across a range of heat fluxes (80–250 W/cm 2 ) and stagnation pressures (1900–7300 Pa) was studied using a combination of in situ imaging and post-test characterizations. The experimental results enabled an assessment of both surface and volumetric ablation mechanisms. A space- and time-dependent Thiele number was computed from the experimental data to characterize competition between rates of chemical reaction and diffusion. The results indicate in-depth oxidation at certain conditions, corroborated by micro-structural analysis.