Sun Gravity-Assist to Trans-Lunar Injection Orbits

Solar gravity propelled highly elliptical resident Earth orbits have been utilized to improve lunar mission performance. A regularized orbit propagator has been used to perform linear search for initial conditions that produce energy-saving pre-trans-lunar injection exo-atmospheric highly elliptical orbits. Additional propellant mass margin or smaller piggyback payloads to the Moon/high altitude orbits may be enabled by such transfers.