Escape Trajectories from Lagrangian Points with Electric Propulsion

An indirect method to determine optimal low-thrust trajectories for the escape from Earth’s sphere of influence starting from Sun-Earth or Earth-Moon L2 is developed. The highly chaotic and non-linear dynamics of motion close to Lagrangian points challenges the remarkable precision of the indirect method: different approaches and improvements, such as multifield and possibly multiple-shooting methods, are identified and implemented to handle these numerical problems. The dynamic model considers 4-body gravitation, JPL ephemeris, and may include spherical harmonic models for Earth and Moon; solar radiation pressure is also considered. Results show single burn escape trajectories from Sun-Earth L2 and the relatively small influence of perturbations on C3 and propellant requirements. Single-burn and two-burn trajectories are required for escape from Earth-Moon L2, with large influence on performance by the relative positions of Sun and Moon.