Optimal outbound transfer windows for Artemis Ⅲ and beyond

The NASA Artemis program will take incremental steps towards establishing a sustainable and long-term human presence in the vicinity of the Moon. Artemis Ⅲ and beyond (Artemis 3+) will leverage a mission architecture that supports science in lunar orbit and on the surface of the Moon. These later Artemis missions will exploit either the Gateway spacecraft, an orbital laboratory in a 9:2 lunar resonant Near-Rectilinear Halo Orbit (NRHO), or the Human Landing System (HLS) in a similar orbit. While the NRHO provides many benefits to operations, the multi-body gravitational regime produces complex dynamics that can make orbital transfers from Earth difficult to optimize. This study provides a comprehensive examination of NRHO rendezvous transfers subjected to operational constraints presented by an Artemis 3+ architecture. An ephemeris model is utilized for the outbound transfer to rendezvous with a 9:2 NRHO bounded by parameters, such as Earth parking orbit, ΔV requirements, and transfer time constraints expected from an Artemis 3+ mission. The model was used to compute ΔV optimal transfers to a rendezvous target at different epochs corresponding to different positions along the NRHO. Next, contour plots were generated for transfer ΔVs across a range of rendezvous epochs and cislunar transfer durations, similar to a porkchop plot. These contour plots allow mission designers to view the entire solution space over a selected window of dates instead of just point solutions for a given epoch. This is particularly useful for a problem that has multiple local minima. While there is already a theoretical understanding of optimal transfers to an NRHO, this work explores transfer and rendezvous optimization in the context of Artemis 3+ operational constraints. Contour plots of the transfer solution space generated in this study are shown to be a valuable tool for constructing continuous and optimal launch windows.