Low-energy transfers to the Moon with long transfer time

This paper globally explores two-impulse, low-energy Earth–Moon transfers in the planar bicircular restricted four-body problem with transfer time of up to 200 days. A grid search combined with a direct transcription and multiple shooting technique reveals numerous families of optimal low-energy solutions, including some that have not been reported yet. We investigate characteristics of solutions in terms of parameters in two- and three-body dynamics, and discuss a trade-off between cost and transfer time based on Pareto-optimal solutions, with and without lunar gravity assists. Analysis of orbital characteristics reveals the role of the Sun, the Earth, and the Moon in the transfer dynamics.