Analytical Investigation of Global Deployed Shape of a Spinning Solar Sail Membrane

In this paper, the deployed shape of spinning square solar sails was investigated through dynamic nonlinear finite element analysis of the full model of the solar power sail of the world’s first solar sail: Interplanetary Kite-craft Accelerated by Radiation of the Sun (IKAROS). The on-orbit photographs of IKAROS revealed that the sail membrane was deformed toward the sun and the membrane maintained its deployed shape during very low-spin-rate operations. To clarify the mechanism of the deformation and high stiffness, the authors of the present study previously performed deployed shape analyses of one-quarter of one square sail by employing Abaqus and reported that the phenomenon was probably caused by curvatures of thin-film devices attached to the membrane. In this study, a finite element model of the entire square sail of IKAROS was created. Furthermore, deployed shape analysis under several combinations of curvatures and spin rates was conducted by employing the dynamic solver “Abaqus/Explicit.” The results indicated that the sail deformations were induced by the curvatures of thin-film devices and that umbrella and saddle shapes appeared owing to the curvatures. The results also indicated that the electric harnesses between the sail and spacecraft supported the sail shape when the spin rate was low.