“…Finally η = 0 represents a constant propulsive acceleration, or a thrust that is independent of the distance from the massive attractor. Actually η = 0 is consistent with a situation in which the propulsion system is either a minimagnetospheric plasma thruster (Winglee et al, 2000;Trask et al, 2004;Mengali and Quarta, 2006), or an electric thruster when the thrust is modulated such as to provide a constant thrust-to-mass ratio (Prussing and Coverstone, 1998;Mengali and Quarta, 2009a) and the power source is independent of the Sun-spacecraft distance, as in a nuclear-powered system. This happens, for example, when the power subsystem is represented by a radio-isotope thermoelectric generator (Hunt, 1993;Lyngvi et al, 2007).…”