Shape-changing solar sails for novel mission applications

In order to increase the range of potential mission applications of solar sail technology, this paper introduces the concepts of shape change and continuously variable optical properties to large gossamer spacecraft. Merging the two concepts leads to the idea of solar sails as multi-functional platforms that can have potential benefits over conventional solar sails by delivering additional key mission functions such as power collection, sensing and communications. To this aim, the paper investigates the static deflection of a thin inelastic circular sail film with a variable surface reflectivity distribution. The sail film is modelled as a single surface framed by a rigid supporting hoop structure. When changing the reflectivity coefficient across the sail surface, the forces acting on the sail can be controlled without changing the incidence angle relative to the Sun. In addition, by assigning an appropriate reflectivity function across the sail, the load distribution due to solar radiation pressure can also be manipulated to control the billowing of the film. By an appropriate choice of reflectivity across the sail, specific geometries can be generated, such as a parabolic reflector, thus enabling a multi-functional sail. This novel concept of optical reconfiguration can potentially extend solar sail mission applications