OPTIMAL LOW-THRUST EARTH-MOON TRANSFERS WITH A SWITCHING FUNCTION-STRUCTURE

A new minimum-fuel, Earth-Moon trajectory problem is examined for a low-thrust spacecraft with engine thrust magnitude controlled by a switching function. The problem is solved in the context of the restricted three-body problem. A direct method is applied to predict the nature of the switching function and allow good initial guesses for the two-point boundary value problem solution. An iterative method is developed which effectively leads to the two-point boundary value problem solution. Several optimal planar Earth-Moon transfers are obtained for a range of fixed end-times. Results are presented for multiple-burn cases ranging from 2 burn/1 coast to 5 burn/4 coast solutions.