Towards Reentry Capsule Dynamic Stability Prediction: Recent Experience using PyFR for Capsule Wake Flow

Planetary reentry capsules are typically blunt shaped to keep the strong leading bow shock away from the capsule and reduce the thermal load on the surface. Although such shapes are preferred for heating in the hypersonic regime of the flight trajectory, they present significant challenges for dynamic stability at the low supersonic and subsonic Mach number regimes. The unsteady wake behind the blunt body exerts forces and moments on the after-body which dictate the stability character of the capsule. Characterization of this unsteady wake is crucial to understand the dynamic stability behavior. Towards the goal of predicting capsule dynamic stability characteristics using CFD, results from a recent PyFR study of the wake behind the Viking '75 reentry capsule will be presented. Also current effort to extend the capabilities of the solver for free-flight prediction will be mentioned.