Dynamics and control of sun-facing diffractive solar sails in displaced orbit for asteroid deflection

A gravity tractor spacecraft propelled by a diffractive sail tracking a displaced orbit offers a potential option for deflecting near-Earth asteroids. This study delves into the preliminary dynamics, evaluates the deflection capabilities, and investigates the stability and control of the diffractive sail on the displaced orbit near the asteroid. Unlike reflective sails, diffractive solar sails generate tangential radiation pressure force, offering multiple advantages. These include the elimination of tilt attitude requirements, no offset angle restrictions from the target asteroid's flight direction, and superior deflection performance with an equivalent area-to-mass ratio when the diffraction angle surpasses 50deg. To maintain position, a controllable diffractive sail model using spatial light modulators, coupled with a feedback control law, is proposed. This control design stabilizes the periodic displaced orbit without necessitating tilt attitude adjustments towards the sun, as validated by our numerical simulations.