Secondary Solar Reflection Thrust Effects on Non-planar Solar Sail Topologies

The classic first-order thrust approximation for solar sails is analytically extended to include the effects of secondary reflections and generalized in a practical Finite Element Model (FEM) based routine. Examination and inclusion of secondary reflection forces are shown to grow increasingly non-trivial as the deformation becomes more extreme. The approach taken herein does not address the “billow” deformation of a sail, rather the focus is on heavily corrugated sail topologies such as those present during the unfolding of a zfolded membrane. First, a second-order thrust estimation for a simple corrugated section is developed. These results are then used to verify an FEM based thrust estimation for a similar generic surface geometry that does not consider any elastic membrane behavior. Finally, the FEM approach is used in characterizing the thrust production of a specific micro-solar sail design with severely corrugated topology. Results show that secondary reflections can have a significant effect on the thrust and control of the sail depending on the craft orientation and the ability of the sail structure to achieve the ideal flat surface.