Nonlinear Effects of the Central Body Oblateness on the Coplanar Dynamics of Solar Sails

The nonlinearities introduced by the coupling of solar radiation pressure and oblateness perturbations are known to yield radical changes in the long-term dynamics of solar sails. After a reduction process in which short-period terms are removed by perturbation theory, we arrive to a time-dependent two-degrees-of-freedom Hamiltonian depending on one physical and one dynamical parameter. While the reduced model is non-integrable in general, coplanar orbits constitute an integrable invariant manifold. We discuss the qualitative features of the coplanar dynamics and find three regions of the parameters space characterized by the existence of different regimes of the reduced flow.