Propellant-Optimal Powered Descent Guidance

摘要

The problem of guiding a rocket-powered vehicle to land on a planet (or the Moon) with pinpoint precision and minimum propellant usage is the focus of this work. Three related but different versions of optimal powered descent problems are formulated with different intended purposes. Comparison and relationships among the solutions to these problems are analyzed. A theoretical investigation reveals the detailed structure of the optimal thrust magnitude profile in the problems and helps significantly simplify the design of the guidance algorithm. An indirect-method-based fast and robust algorithm is developed to solve these problems. Another unique contribution of this paper is a novel and simple strategy to adaptively determine onboard a desirable powered descent initiation condition so that no major divert is required of the powered descent trajectory. The algorithm is demonstrated in closed-loop simulations for a human Mars mission where a significantly heavier landing mass and more stringent landing precision are required than in any robotic missions thus far.