Fast and robust computation of low-thrust orbit-raising trajectories

Abstract

This paper presents a new dynamic model of a thrusting spacecraft, and the model is used for computing low-thrust orbit-raising trajectories to the geosynchronous equatorial orbit. Low-thrust orbit raising is a challenging problem, owing to numerous revolutions and multiple eclipses encountered during the long transfer. The paper also presents a mathematical framework that poses the orbit-raising problem as a sequence of multiple unconstrained optimization subproblems, with each subproblem attempting to minimize the deviation of the spacecraft's orbit from geosynchronous equatorial orbit at the end of one revolution. We demonstrate the application of the developed framework through numerical examples corresponding to planar and nonplanar orbit-raising scenarios. Simulation studies indicate that orbit-raising scenarios can be solved quickly and demonstrate robust convergence, without requiring the need for any user-input initial guess. This advantage is obtained at the cost of suboptimality of the generated solutions, and an estimate of the optimality gap is provided by comparing the computed solutions with those available in the literature.