“…First studies of optimization problems for electric-propulsion spacecraft using simplified models of real gravity fields produced a number of analytic solutions, which facilitated engineering research. Due to this historical phenomenon, at the current stage, which is undoubtedly timely [36,39,40,48,50,53,61,68,72,73,75,76,78,82], the practical development of advanced orbital transfer electric-propulsion vehicles leans upon an unusually and favorably solid theoretical footing.…”