Fuel Optimal Earth-Moon Transfer Trajectories Using Low-Thrust

Abstract

In this thesis, a new method to yield an initial guess for the inertial frame and the Earth-Moon rotating system are proposed to solve a fuel optimal, specific energy targeting problem. The proposed initial guess structure can provide estimated initial costates which are converged to the solutions efficiently. The new method for the initial guess comes from initial costates properties of the specific energy targeting problem. Through several examples, this method is able to efficiently produce solutions for the arbitrary central planet, long transfer time, initial radius, and terminal target-specific energy conditions. A design procedure for the optimal Earth-Moon trajectory governed by the restricted three-body dynamics in the rotating frame is also introduced and discussed. The first and second steps are that a specific energy targeting problem with respect to the Earth and the Moon respectively in the Earth-Moon rotating frame. When the new method for the initial guess of specific energy targeting problem is considered as the first step, the proposed procedure reduces the design steps comparing to those of the previous works. Additional feasibilities of the solutions of step 1, 2 are inspected by numerical integration for the third step’s problem. At each step of the proposed procedure, the sub-optimal problems and the design techniques are also discussed. The proposed procedure is applied to find the transfer orbit from the 315 km-low circular Earth to 100 km-low lunar orbit with a flight time of 73 days. And also, optimal Earth-to-Moon trajectories are presented with a combined impulse type thruster and Variable Specific Impulse(VSI) type low thruster. For the problem, restricted three-body dynamics is considered, whereas other perturbed forces are not considered for the analysis of baseline trajectories. In the Earth escape phase, the transfer time is a critical issue due to the Van Allen radiation belt. Therefore, an impulsive type thruster is used i...