Proposal for a light solar sail structure and its deployment

Existing solar sail designs have relied extensively on radial stiffeners and centrifugal force derived from rotation to maintain the shape of a membrane in space. For future large area solar sail missions (>1 km
²
), the former contributes greatly to the weight of the sail while the latter leads to attitude control problems. It is of general interest to have a more effective method of tensioning the membrane without degrading the solar sail performance. Here we propose a sail, shaped like a cone, which redirects the incident solar radiation force to suitably tension itself against deformation. Advantages of the new design are highlighted by computing the performance parameters for a hypothetical, nano-satellite mission and comparing it with existing mission designs. The feasibility of stowing the cone-shaped reflector into a compact form is demonstrated by proposing a suitable folding technique and deployment method. An origami-based folding technique, proposed for flat membranes, is adapted to suit the new shape and mathematical formulations of the fold parameters are presented. A passive deployment scheme using torsional springs located circumferentially along the edge of the membrane is developed and verified by deployment experiments using a small scale membrane model. A numerical lumped mass membrane model was developed to simulate the dynamics of the membrane in space. The accuracy of the numerical model was assessed by comparison with Earth-based experiments. The numerical model was further used to predict the membrane behaviour in space under failure conditions such as asymmetric loading and localized membrane deformations.