Abstract. With the discovery of water ice at the moon's south pole, future human lunar exploration will likely occur at polar sites and, therefore, require high inclination orbits. Also of importance for human missions is the capability to abort if unfavorable circumstances arise. This work addresses both of these concerns by developing an automated, systematic architecture for constructing minimum-fuel, multi-maneuver lunar orbit insertion sequences while providing a ballistic abort option on a free return trajectory. A procedure for free return generation in the circular restricted three-body problem is presented first. No trial and error is required to generate the initial estimate. The automated algorithm is used to generate families of free return orbits for analysis. Next, a targeting and optimization procedure is developed to transfer the spacecraft from the free return trajectory to a closed lunar parking orbit in the four-body ephemeris model. The initial estimate procedure is automated, and analytical gradients are implemented to facilitate optimization. An impulsive engine model is used before conversion to a finite thrust model.
Optimal control theory is then applied and the results are compared with the linearly steered thrust model. Trends in the cost and flight time for various orbit insertion sequences are analyzed.