Solar sailing near the Sun: A comparison study between point-like and spherical-like Sun models

A study on the behavior of flat and spherical solar sails near the Sun is performed for two Sun models, a point-like model and a spherical-like model. The study is carried on by taking into account two prominent effects near the Sun, Poynting-Robertson effect for high velocities and variation in solar disk intensity. Limb darkening effect has been applied as a model for the variation in solar disk intensity over the wavelength lambda is an element of [302.5, 997.5]nm. Acceleration equations for absorption and specular reflection has been developed analytically for spherical sails and flat sails at normal orientation for the spherical model with limb darkening and Poynting-Robertson effect. As a result of the spherical Sun model, in general, escape trajectories show a large decrease in solar sail speed and overall distance in comparison with the point model. Furthermore, for heliocentric bound orbits, large degradation in radial distance over the period of the solar sail mission is found, accompanied with trajectory oscillation. Between the two solar sail configurations, at close encounter to the Sun, the optimal choice is dependent on the possible values of reflectivity and absorptivity.