Space low-thrust trajectory optimization utilizing numerical techniques, a comparative study

The aim of this paper is to solve nonlinear optimal control problem which is achieving maximum radius orbit transfer in a given time utilizing indirect methods including Steepest Descent, Variation of Extremals, Quasilinearization and Collocation Methods. To determine the best method, comparisons are made in the terms of accuracy, the rate of convergence, sensitivity to initial guess and the time of computer processing and then the results are analyzed. In other words, the purpose is to extract the features of the discussed methods in terms of the defined criteria and propose the optimal method for the control problem.