Optimal Earth-Moon Trajectories Using Combined Chemical-Electric Propulsion

Abstract

Minimum-fuel, three-dimensional Earth ‐moon trajectoriesareobtainedforspacecraftusing bothchemicaland electricpropulsion stages. The problem involvesmaximizing thee nal spacecraft mass delivered to a circular, polar midlunarorbit. Themissiondee nition involvesa chemical-stageboostfrom low-Earthorbitinto acoasting ballistic trajectory followed by a lunar capture trajectory performed by the electric propulsion stage. For this analysis, the ballistic orbit transfer and the powered orbit transfer to a circular orbit within the lunar sphere of ine uence are modeled by the dynamics of the classical restricted three-body problem, and two body-centered coordinate frames are utilized. The subsequent descending three-dimensional spiral trajectory to circular polar midlunar orbit is computed via Edelbaum’ s analytic equations in order to eliminate the need to numerically simulate the numerous near-circular lunar orbits. Two classes of current-term electric propulsion thrusters are utilized (arcjet and plasma thrusters ) along with current-term launch vehicle cone gurations. Numerical results are presented, and the optimal chemical ‐electric propulsion transfers exhibit a substantial reduction in trip time compared to Earth‐moon transfers using electric propulsion alone.