The goal of this project is to advance the state of the art with regard to low thrust trajectory optimization in 3-body and 4-body force models, specifically in Earth-Moon space. The proposed research will bring together two areas of space exploration capability that have each brought new kinds of missions to the table: electric propulsion (equivalently referred to as “low thrust propulsion” or “solar electric propulsion”) and low-energy transfers. These two areas of study have mostly existed in isolation from each other. The proposed research will explore how bringing them together can be an enabling space technology, and it will quantify the resulting mission benefits and risks. This research will be conducted at the University of Colorado using high fidelity numerical simulations, using code developed specifically for this research and also code that has been developed in the research center to address many similar problems. The trajectory solutions will be validated with NASA software. Some of the questions that will be addressed include: What existing optimization methods for low-thrust trajectories are most suitable for onboard computation? What new missions can be enabled with active thrusting to transfer between halo orbits? Some of the perceived benefits are: reduced mission design time; reduced time of flight, traded with fuel cost; and new types of missions enabled.