Vibrational-Chemical Kinetics in Mars Entry Problems

Abstract

The paper deals with kinetic theory methods modelling of reacting gas flows near spacecrafts entering the Mars atmosphere. For mixtures containing CO2 molecules, the complete kinetic scheme including all vibrational energy transitions, dissociation, recombination and exchange chemical reactions is proposed. For the prediction of gas dynamic parameters and heat transfer to the surface of a spacecraft, a detailed approach taking into account state-to-state CO2 vibrational and chemical kinetics as well as multi-temperature approaches based on quasi-stationary vibrational distributions are used. A more accurate but complicated and time consuming state-to-state model is applied for the numerical simulation of a one-dimensional flow in a boundary layer near the entering body surface. More simple quasi- stationary three-temperature, two-temperature and one-temperature approaches are used for the numerical study of a 2-D viscous shock layer under entry conditions. The vibrational distributions near the surface are far from the local vibrational and chemical equilibrium and a noticeable difference is found between the values of CO2 vibrational-specific energies at the surface obtained by means of the state-to-state and quasi-stationary approaches. At the same time, for all considered approaches, the kinetic model for vibrational distributions and chemical reactions has a weak influence on the heat transfer to the non-catalytic vehicle surface.