On-board entry trajectory planning for sub-orbital flight

An algorithm for on-board planning of sub-orbital entry trajectories is presented. For entry vehicles with low lift-to-drag ratios and entering entry flight at sub-orbital speeds, this algorithm fills a gap left in a recently developed methodology for on-board generation of three-degree-of-freedom (3DOF) entry trajectories. The algorithm developed in this paper is able to reliably generate a 3DOF feasible sub-orbital entry trajectory in a time frame compatible with on-board environment. The combination of this algorithm and an algorithm recently developed for orbital entry missions provides the capability for full-envelope autonomous adaptive entry guidance. The current algorithm is validated by extensive high fidelity simulations using a sub-orbital reusable launch vehicle model and difficult mission scenarios including failures and aborts.