In this paper, it is studied to optimize trajectories of a satellite passing through the shadow area of the Earth using electric propulsion system for transferring orbits.
Electric propulsion system has lower thrust and higher specific impulse than chemical propulsion system. Therefore, the total mass of propellant for satellite mission can be reduced. For these reasons, electric propulsion system has been applied to an interplanetary mission and deep space mission. In addition electric propulsion system is utilized for attitude control for low thrust.
Electric propulsion system has to be applied to a small satellite in a tentative way for acquisition of orbit transfer technology. Considering the missions of the small satellites which are carried out on a low earth orbit, it is important that the satellite is in the earth’s shadow area. During this time, supplying electric power to the satellite is going to be difficult due to the solar array which is under insufficient sun power. Henceforth, the Earth’s shadow effect should be taken into account for obtaining optimal trajectory for orbit transfer.
There are numerous numerical optimization techniques. While the direct method requires many parameters to get a solution, the indirect method needs a few. In addition, orbit transfer time is not specified, it is difficult to get final time using the direct method. For this reason, optimal trajectory was calculated using the indirect method.
And the fact of turning off the electric propulsion system in the earth shadow area mean that it is possible to ON/OFF control of electric propulsion system. Therefore, in this study, the variable thrust system is also considered with direction control of thrust vector.