Experimental and Modeling Investigation of CO2 Dissociation in Mars Entry Condition

Shock tube experiments are carried out to study the physical and chemical processes during a vehicle entry into the Mars atmosphere. The facility to establish a strong shock wave is a shock tube which is driven by combustion of hydrogen and oxygen. Measurements of rotational and vibrational temperature behind the shock wave are realized thanks to optical emission spectroscopy (OES). In parallel, tunable diode laser absorption spectroscopy (TDLAS) is utilized to diagnose one absorption line of CO near 2.33 mu m. Combined with these temperature results using OES, CO concentration in the thermal equilibrium region is derived, which is 2.91 x 10(17) cm(-3), corresponding to equilibrium temperature equals to 7000 +/- 400 K. Moreover, a thermochemical code, based on Park's two-temperature theory, for studying chemical and physical processes is developed for Mars entry conditions. Some comparisons between experiments and calculations are presented. Such a two-temperature model fails to reproduce non-equilibrium temperatures and mole fractions but suitable for equilibrium temperature predictions.