Numerical Investigation of Aerodynamic Stability Derivatives of Atmospheric Entry Vehicle

Abstract

An atmospheric entry vehicle (AEV) design is the most critical component of planetary exploration with an appreciable atmosphere. A successful design demonstrates manageable aerodynamic heating, bearable structural load, smooth deceleration, and intended trajectory during a descent into the atmosphere. Interestingly, the supersonic regime of the AEV manifests limit cycle oscillations (LCO) that restrict the maneuver potential and deployment of the drag chute. Efforts are made numerically and analytically to link the causation of LCO with external geometric variables of AEV, apex angle, and characteristics length. For this, Unsteady Reynolds-Averaged-Navier-Stokes equations are used to calculate damping derivatives through the forced oscillation technique. The numerical results are validated with the NASA Orion Crew Exploration Vehicle (CEV). The multiple time scales (MTS) method, which belongs to the class of perturbation methods, is used to develop an approximate closed-form solution of the nonlinear dynamical behavior of AEV. The analytical solution identifies that cubic nonlinearity, associated with pitch damping and static lift, significantly governs the onset of LCO. Finally, a parametric interaction study is carried out to determine the effect of two design variables, apex angle, and length, on the vehicle’s dynamic stability using the Design of Experiment (DOE). The mean data values from the main geometric effects plot show the condition at which finite-amplitude oscillations will occur. The results indicate that the variation in the apex angle significantly impacts the magnitude of identified cubic nonlinearities.