Near-Optimal Guidance and Pulse-Modulated Reduced-Attitude Control for Orbit Injection

In most mission scenarios, precise orbit injection represents a crucial requirement, and affects the subsequent phases of spaceflight. This research proposes a new guidance, control, and actuation architecture for upper stage orbit injection maneuvers. A novel, explicit near-optimal guidance algorithm is developed that is based on the local projection of the position and velocity variables, in conjunction with the real-time solution of the associated minimum-time problem. A new, nonlinear reduced-attitude control algorithm is introduced, which enjoys quasi-global stability properties, and is capable of driving the actual longitudinal axis toward the commanded thrust direction. Actuation is based on the joint use of modulated side jets – for the roll control action – and thrust vectoring. The overall dynamics of the upper stage, regarded as a system of two connected bodies, is modeled using Kane’s method. An upper stage with realistic propulsion parameters is selected for numerical testing. Monte Carlo simulations prove that the guidance, control, and actuation architecture at hand is effective for precise orbit injection.