Hypersonic flow over Stardust Re-entry Capsule using ab-initio based chemical reaction model

Abstract

Hypersonic air flow around the Stardust Re-entry Vehicle for diverse ambient conditions is investigated using the Direct Simulation Monte Carlo (DSMC) method. In the present work, the flow field and surface properties on the re-entry vehicle are compared for simulations employing two different chemical reaction models: the traditional phenomenological Total Collision Energy (TCE) model and a new chemical reaction model based on ab-initio principles. The reactive cross-section used in the new chemical reaction model are calculated using Quasi-Classical Trajectory method and employs highly accurate Potential Energy Surfaces. Conditions prevailing at 68 km, 80 km and 100 km are simulated and for two re-entry speeds. It is found that the DSMC simulations with the new ab-initio based chemical reaction model predicts higher heat flux and heat load on the re-entry vehicle surface compared to the simulations employing the TCE model. The difference in the heat flux predicted by the two models is most evident at 80 km. This is a significant inference for engineers designing the Thermal Protection Systems. It is observed that there are significant differences in the estimation of mole fraction of NO by the two models. The limitations of the present model and future scope are discussed in detail.