Evaluation of Hypervelocity Carbon Dioxide Blunt Body Experiments in an Expansion Tube Facility

Abstract

This work represents efforts to study high-enthalpy carbon dioxide flows in anticipation of the upcoming Mars Science Laboratory (MSL) and future missions. The current study extends the previous presentation of experimental results by the comparison now with axisymmetric simulations incorporating detailed thermochemical modeling. The work is motivated by observed anomalies between experimental and numerical studies in hypervelocity impulse facilities. In this work, experiments are conducted in the Hypervelocity Expansion Tube (HET) which, by virtue of its flow acceleration process, exhibits minimal freestream dissociation in comparison to reflected shock tunnels. This simplifies the comparison with computational result as freestream dissociation and considerable thermochemical excitation can be neglected. Shock shapes of the Laboratory aeroshell and spherical geometries are compared with numerical simulations. In an effort to address surface chemistry issues arising from high-enthalpy carbon dioxide ground-test based experiments, spherical stagnation point and aeroshell heat transfer distributions are also compared with simulation. The shock stand-off distance has been identified in the past as sensitive to the thermochemical state and as such, is used here as an experimental measureable for comparison with CFD and two different theoretical models. For low-density, small-scale experiments it is seen that models based upon assumptions of large binary scaling values are unable to match the experimental and numerical results. Very good agreement between experiment and CFD is seen for all shock shapes and heat transfer distributions fall within the non-catalytic and super-catalytic solutions.

Files

Additional details