MODELING OF CATALYTIC REACTIONS ON SILICA SURFACES WITH CONSIDERATIONOF SLIP EFFECTS

A detailed surface chemistry model is presented for the reactions of N -2, O-2, NO, N, and O on a silica surface, The model distinguishes ads orption, desorption, and recombination reactions according to the Eley -Rideal and Langmuir-Hinshelwood mechanisms as well as dissociative ad sorption reactions of the molecular species, The model parameters are adjusted by comparison of predicted recombination coefficients for N a nd O with experimentally determined recombination coefficients. For th e calculation of surface heating rates of re-entry vehicles, the model is implemented into a multiple-temperature Navier-Stokes code and cou pled with a slip model to take into account rarefaction effects at hig h altitudes. Computational results obtained with the surface chemistry model for Shuttle-equivalent hyperboloids are compared to Shuttle fli ght data.