Refined solar sail force model with mission application

The aim of this paper is to propose a refined mathematical model for describing the acceleration experienced by a solar sail. Unlike the conventional model characterized by constant coefficients, the force coefficients of the sail are now assumed to depend on the light incidence angle, the sail surface roughness, and the sun-sail distance. The new model is elaborated with the support of experimental data that show how the main variable affecting the force coefficients is the light incidence angle. To emphasize the differences between the refined force model with respect to the conventional one, a comparison is established through the analysis of a circle-to-circle interplanetary rendezvous problem between coplanar orbits. The problem is solved using an indirect approach and the optimal steering law is approximated in polynomial form. A number of optimal trajectories toward Mars and Venus are simulated and the results obtained are discussed as a function of the dimensionless sail loading parameter and the sail surface roughness.