Abstract: Optimal control methods are applied to a class of minimum-fuel
Earth-moon transfers from a circular low Earth parking orbit to a circular low
lunar parking orbit for low-thrust propulsion systems with thrust-to-weight
ratios on the order of 0.001 to 0.0001. The optimal trajectory is restricted to
a thrust-coast-thrust sequence. Several special numerical techniques are
required to enhance convergence to a solution. Both two- and three-dimensional
numerical results will be presented. In the latter case, the lunar parking
orbit is inclined 90 degrees from the Earth-moon plane.