QEGC-based time-coordinated analytical entry guidance for reentry glide vehicles with irregular no-fly zones

Entry guidance for near-space reentry vehicles is increasingly challenged by stringent terminal constraints in complex mission scenarios, particularly in the presence of irregular no-fly zones (NFZs). To address this issue, this paper studies a time-coordinated entry guidance problem for reentry vehicles subject to irregular NFZ constraints. For longitudinal guidance, an analytical guidance law is developed under the quasi-equilibrium glide condition, from which the reference flight path angle and reference altitude rate are generated analytically. Based on these reference quantities, an LQR-based correction is introduced to compensate the approximation error of the analytical guidance law, suppress altitude oscillations, and improve terminal constraint satisfaction. To incorporate arrival-time requirements without resorting to iterative schemes, terminal velocity is treated as an online adjustable variable, enabling effective coordination between range-to-go and time-to-go. On the lateral side, irregular NFZs are represented by a set of minimum covering circles generated through constrained Delaunay triangulation with pre-inserted interior points, from which a compact heading angle corridor is constructed for avoidance. Numerical simulations verify the robustness of the proposed guidance method against initial-state perturbations and its effectiveness in handling irregular NFZs.