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Entry Guidance Based on Analytical Trajectory Solutions

Analytical entry guidance is designed to control the atmospheric gliding of a hypersonic glider. The guidance uses only approximate analytical solutions for a 3-D hypersonic gliding trajectory to fast plan reference trajectory onboard and thus has an extremely high computational efficiency. To reduce the amount of calculation, the adopted analytical solutions are improved first such that their coefficients depend only on generalized flight states. As the coupling of longitudinal and lateral dynamical equations is fully considered, the analytical solutions are of high accuracy but complicated, which consist of zeroth-and first-order solutions. To resolve the resulting difficulty of trajectory planning, an efficient scheme is proposed. In the first guidance cycle of steady glide, the scheme uses only the zeroth-order solutions to plan a trajectory rapidly. In the subsequent guidance cycles, the scheme first uses some profiles obtained from the previously planned trajectory to specify part of the coefficients of the zeroth-and first-order solutions in order to offset the impact of the equations coupling and then utilizes the complete solutions to update the trajectory by proposing a method based on a virtual endpoint of glide and virtual terminal crossrange, which can achieve a very small terminal heading error. The superiority of the guidance is demonstrated by conducting Monte-Carlo simulations.