Onboard generation of three-dimensional constrained entry trajectories

A methodology for very fast design of three-degree-of-freedom (3DOF) entry trajectories subject to all common inequality and equality constraints is developed. The approach makes novel use of the quasi-equilibrium glide phenomenon in lifting entry as a centerpiece for effective and efficient enforcement of the inequality constraints. The highly constrained nonlinear trajectory planning problem is decomposed into two sequential one-parameter search problems. The algorithm is able to generate a complete and feasible 3DOF entry trajectory of 25-min flight time in about 2-3 s on a desktop computer, given the entry conditions, values of constraint parameters, and final conditions. High-fidelity numerical simulations with a reusable launch vehicle model for various entry missions and trajectory planning using the space shuttle model are presented to demonstrate the capability and effectiveness of the algorithm.