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.
