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

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