Detailed DSMC surface chemistry modeling of the oxidation of light-weight carbon preform ablators

A detailed finite-rate surface chemistry model which incorporates various standard surface reaction mechanisms was implemented in a direct simulation Monte Carlo (DSMC) solver. The DSMC code SPARTA was used to perform detailed simulations of the various reaction mechanism at different conditions to obtain the measured time-of-flight distributions and angular distributions of the products. The information from this study was used to derive a finite rate oxidation model directly from detailed surface scattering experiments of hyperthermal O reacting with Vitreous Carbon. The surface chemistry model was found to provide excellent agreement with the experimental TOF and angular distributions over a range of temperatures and oxygen surface coverage. The obtained rates were then applied to study the same hyperthermal O beam bombarding a porous fibrous carbon fiber material used as preform for Thermal Protection Systems, FiberForm. The numerical results of the interaction between the molecular beam and FiberForm are studied in detail at the highest temperature of 1823 K. Additionally, the numerical distributions obtained for Vitreous Carbon and FiberForm were compared at 1823 K, and it the main observed feature was the increase in the fraction of products desorbing from the surface thermally accommodated, as well as an increase in the ratio of CO/O products.