Self-Stabilization of Light Sails by Damped Internal Degrees of Freedom

We consider the motion of a light sail that is accelerated by a powerful laser beam. We derive the equations of motion for two proof-of-concept sail designs with damped internal degrees of freedom. Using linear stability analysis, we show that perturbations of the sail movement in all lateral degrees of freedom can be damped passively: the sail is asymptotically stable. This analysis also shows complicated behavior akin to that associated with exceptional points in PT-symmetric systems in optics and quantum mechanics. We show that the excess heat that is produced by the damping mechanism is likely to be substantially smaller than the expected heating due to the partial absorption of the incident laser beam by the sail.