Optimization of Refueling Strategies for Electric Propulsion Space Missions

This paper presents an analytical framework for optimizing refueling strategies for space missions using electric propulsion assuming the availability of in-space refueling stations. The authors derive analytical expressions for key performance metrics, including normalized payload and structure mass, firing time ratio, and specific propellant consumption. They demonstrate that an evenly distributed refueling sequence maximizes the payload mass and that the optimal specific impulse decreases as the number of refueling stations increases. Additionally, the authors extend the concept of the Stuhlinger characteristic velocity to incorporate refueling. Finally, an optimization problem is formulated to determine the ideal refueling sequence that maximizes payload under constraints on the mission time within practical mission constraints. Using the SMART-1 mission as a case study, the authors illustrate the potential of their refueling optimization approach to significantly increase payload mass and reduce specific propellant consumption at the expense of a slightly longer mission time.