New Nonlinear Control Technique for Ascent Phase of Reusable Launch Vehicles

Abstract

Modifications and extensions to a recently developed hybrid numerical-analytical method for optimization of future launch vehicles are presented, to allow for the real time generation of abort trajectories. A set of terminal constraints is formulated that targets an entry condition for the abort case and allows the vehicle to attach tangentially to a nominal entry path. The trajectories are optimal in the sense of maximizing terminal energy. In addition, the algorithm has been extended to include path constraints on both angle of attack and q . α. A second issue addressed concerns the possibility of singular arcs, both for nominal ascent and aborts. It is proven that such arcs are not feasible, both within the atmosphere and in vacuum, when the control variables consist of body attitude and throttle. Finally, numerical results for different abort scenarios using a single-stage vehicle model illustrate both the capabilities and some of the deficiencies of the approach.