Optimal impulsive orbit transfers from gateway to low lunar orbit

Gateway represents a key element of the Artemis program for the upcoming lunar exploration aimed at establishing a sustainable presence by the mid-2030s. This paper investigates minimum-fuel bi-impulsive orbit transfers from Gateway to low lunar orbits (LLOs) with a maximum time of flight of 48 h. Two distinct scenarios are analyzed: (i) target orbits with free right ascension of the ascending node (RAAN), and (ii) target orbits with specified RAAN. For case (i), a global optimization technique based on a heuristic algorithm is exploited to obtain the minimum-fuel transfer. Several inclinations of the target orbit are considered. For case (ii), two distinct techniques are proposed: (a) a purely heuristic approach, and (b) a semi-analytical method based on local refinement of a Lambert-based solution. Numerical propagations are conducted in all scenarios in a high-fidelity framework that includes all relevant perturbations. A comparison between the different strategies and the related numerical results is provided.