Structural and Control Concepts for Variable Geometry Planetary Entry Systems

The results presented in this paper apply to a generic vehicle that makes use of geometry changes to modulate the heat, drag, and acceleration loads while entering a planetary atmosphere. Two structural concepts for implementing the cone angle variation, namely a segmented shell and a corrugated shell, are presented. A structural analysis of the corrugated shell configuration shows that the stress levels are tolerable during entry. The analytic expressions of the longitudinal aerodynamic coefficients are also derived, and guidance laws that track reference heat flux, drag, and aerodynamic acceleration loads are also proposed. These guidance laws have been tested in an integrated simulation environment, and the results indicate that use of variable geometry is feasible to track specific profiles of dynamic load conditions during reentry.