Embedding Performance Optimization and Constraint Enforcement into Heritage Powered Descent Guidance

Heritage powered descent guidance laws from the Apollo era, such as the Apollo Lunar Descent Guidance and E-Guidance laws, are valued for their analytic simplicity, robustness, and flight-proven maturity. Yet they lack automated methods for initializing time-to-go, enforcing inequality constraints, and optimizing performance. This paper presents an approach that embeds these capabilities within the Fractional Polynomial Powered Descent Guidance ([Formula: see text]) laws, a modern embodiment and extension of the Apollo-era guidance laws. By optimizing the [Formula: see text] parameters and the initial time-to-go, a compact nonlinear programming problem of dimension three is solved to minimize propellant usage while satisfying thrust limits and other trajectory constraints. The problem has closed-form expressions and can be solved rapidly, making onboard implementation feasible. The numerical investigation shows that the optimized [Formula: see text] law can achieve propellant efficiency closely comparable to that of modern propellant-optimal guidance algorithms, effectively enforce physical and operational constraints, and be capable of supporting autonomous divert and hazard avoidance maneuvers, all with the simplicity and maturity of Apollo-era guidance.