Experimental and Numerical Study of Carbon-Dioxide Dissociation for Mars Atmospheric Entry

Abstract

The mechanism of dissociation during entry in the Mars atmosphere is experimentally investigated. A hydrogen–oxygen combustion-driven shock tube is used to simulate physical and chemical conditions in a mixture. Two shock velocity/initial pressure conditions are studied: at 100 Pa (called the low-pressure condition) and at 300 Pa (called the high-pressure condition). The temperature behind the shock wave is obtained by analyzing the high-temporal-resolution and high-spatial-resolution experimental spectra of the CN violet (, ) system. The CO number density is derived using a tunable diode laser absorption spectroscopy system based on CO absorption near . Moreover, a numerical code is developed to reproduce the experimental results (temperatures and species densities). The kinetic code in this work is based on Park’s two-temperature model. Comparisons between experiments and calculations are presented. Such a relatively simple two-temperature model fails to accurately describe the nonequilibrium temperature and CO number density but is suitable for equilibrium temperature predictions.