Solar Sail Near-Optimal Circular Transfers with Plane Change

Near-minimum time interplanetary trajectories between circular orbits with different orbital planes are investigated. By assumption, the mission is carried out with a solar sail spacecraft, whose performance takes into account the optical characteristics of the sail film and the maximum temperature constraint. In an effort to obtain a general, albeit approximate, solution, the problem is tackled by dividing the mission in two or three phases, depending on the value of the inclination change between the initial and target orbit. Each phase is analyzed by solving a minimum time problem with an indirect approach, and the whole mission time is estimated as the sum of the contributions of the elementary phases. The obtained results are then collected through graphs and fitting functions that can be used effectively to get a good and quick estimate of the main mission parameters, as well as to quantify their effect on the mission flight time. A comparison of the proposed approach with the optimal results available for the Solar Polar Imager mission confirms the effectiveness of the developed methodology.