Experimental and Numerical Investigation of Hypervelocity Carbon Dioxide Flow over Blunt Bodies

This paper represents ongoing efforts to study high-enthalpy carbon dioxide flows in anticipation of the upcoming Mars Science Laboratory and future missions. The work is motivated by observed anomalies between experimental and numerical studies in hypervelocity impulse facilities. In this study, experiments are conducted in the hypervelocity expansion tube that, by virtue of its flowacceleration process, exhibitsminimal freestreamdissociation in comparisonwith reflected shock tunnels, simplifying comparisonwith simulations. Shock shapes of the laboratory aeroshell at angles of attack of 0, 11, and 16deg and spherical geometries are in very good agreementwith simulations incorporating detailed thermochemical modeling. Laboratory shock shapes at a 0 deg of attack are also in good agreement with data from the LENS X expansion tunnel facility, confirming results are facility-independent for the same type of flow acceleration. The shock standoff distance is sensitive to the thermochemical state and is used as an experimental measurable for comparison with simulations and two different theoretical models. For low-density small-scale experiments, it is seen thatmodels baseduponassumptions of large binary scaling values donotmatch the experimental andnumerical results. In an effort to address surface chemistry issues arising in high-enthalpy groundtest experiments, spherical stagnation point and aeroshell heat transfer distributions are also compared with the simulation. Heat transfer distributions over the aeroshell at the three angles of attack are in reasonable agreement with simulations, and the data fall within the noncatalytic and supercatalytic solutions.