A Simple Semi-Analytic Model for Optimum Specific Impulse Interplanetary Low Thrust Trajectories

This paper describes a simple semi-analytic model for interplanetary solar electric low thrust trajectories. A description is given of a performance model that accurately and quickly models optimum specific impulse circular-coplanar low thrust transfers with a series of simple empirical and physics based relationships that can be implemented easily in a spreadsheet. The paper describes the development methodology, identifies governing variables and fundamental relationships, and presents a model that efficiently calculates system parameters (delivered mass, optimum specific impulse, and ΔV) for a wide range of trajectories. Models are presented for Earth-Jupiter/Trojan Asteroid, Earth-Mars, MarsEarth, Earth-Venus, and Earth-Main Belt Asteroid transfers using solar electric propulsion. The results show good agreement for estimates of both delivered mass (+8%/-15%) and optimum specific impulse (+20%/-20%). The paper also describes progress made towards development of a generalized model that encompasses spacecraft operating at a fixed nonoptimum specific impulse. Results are presented showing good agreement (+/-15%) for a specific Earth-Jupiter transit modeled using the generalized model.