Rapid Design and Exploration of High-Fidelity Low-Thrust Transfers to the Moon

Spiral trajectories to the Moon present a difficult trajectory design problem. In this paper we show that the well-known Q-Law guidance algorithm can be leveraged to rapidly produce near optimal, high fidelity trajectories. By combining forward and backward propagated Q-Law, continuous trajectories are generated from an Earth parking orbit to a target Lunar orbit. The Q-Law result can then be refined using direct collocation. To demonstrate this process, we solve a problem inspired by the SMART-1 mission and compare to literature results. Then, an ESPA-class mission scenario is analyzed. We demonstrate that this technique can be used to efficiently explore the trajectory trade space and provide suitable initial guesses for direct optimization.