A New Model for the Planetary Radiation Pressure Acceleration for Solar Sails

Abstract

Solar sailing is a propellantless propulsion method that takes advantage of solar radiation pressure to generate thrust. The last decades have seen the launch of several solar-sail missions to demonstrate the technology’s potential for space exploration and exploitation. Even more missions are scheduled for launch in the near future, including NASA’s ACS3 and NEA Scout missions and Gama’s Alpha sailcraft. Although most of these sailcraft have flown – or will fly – in LEO, where the planetary radiation pressure is strong (up to approximately 20% of the solar radiation pressure), studies on the perturbing accelerations produced by the Earth’s albedo and blackbody radiation have been conducted only to a very limited first-order extent. This paper therefore provides a novel, detailed analytical model for these perturbing accelerations, valid for double-sided perfectly reflecting solar sails. The underlying assumptions of the model are presented and its full derivation is described. A thorough analysis of the blackbody and albedo radiation pressure accelerations is conducted for a variety of orbital conditions and Sun-Earth-sail configurations. In order to quantify the accuracy of the model, a comparison with the state of the art (the finite-disk radiation source model) is provided. Ultimately, a variety of analyses to quantify the effect of Earth’s albedo and blackbody radiation on the maneuvering capabilities of solar sails are provided, using the orbit of the ACS3 mission as reference scenario. These analyses show that, for an orbit-raising steering law, losses in the altitude gain of 19.6% of the total gain are incurred over a 10-day orbit-raising period. Similarly, losses in the inclination gain of up to 25% of the total gain are observed when implementing an inclination-changing steering law. These results highlight the non-negligible effect of uncontrolled planetary radiation pressure acceleration on the maneuvering capabilities of solar sails in LEO.