Towards 100-metre class monolithic space structures: Methods to ensure sail flatness for extremely large solar sails

Two novel approaches to maximise structural flatness and minimise perturbation solar radiation torque on 100 m class interplanetary solar sails are presented. First, allowing the length of central tethers to be actuated to maximise sail flatness in orbit. Second, replacing the central tether with rigid booms with controllable length and extension angle, to move the centre of solar radiation pressure with respect to the centre of mass. The performance of the above two methods are analysed by using analytical and numerical techniques. While the large sail size requires a high degree of sail flatness (<1 degree), the results show that the two methods can satisfy this requirement, paving the way towards 100 m class deployable space structures, and an entirely new class of space missions.