Theory of radiation pressure on a diffractive solar sail

Abstract

Solar sails propelled by radiation pressure enable space missions that cannot be achieved using chemical rockets alone. Significant in-space propulsion for missions such as a solar polar orbiter may be achieved with a sail that deviates sunlight at a large average angular direction. The momentum transfer efficiency of sunlight diffracted from a Sun-facing diffractive sail comprising periodic right prism elements is examined here. The spectrally averaged efficiency, integrated across the solar blackbody spectrum, is found to approach that of a monolithic prism when the grating period is much longer than the peak of the solar spectrum. This idealized diffraction analysis predicts a greater transverse radiation pressure force compared to an idealized reflective sail. With modern optical design and fabrication techniques, optimized diffractive solar sails may one day replace reflective sails.