Packaging of thick membranes using a multi-spiral folding approach: Flat and curved surfaces

Elucidating versatile configurations of spiral folding, and investigating the deployment performance is of relevant interest to extend the applicability of deployable membranes towards large-scale and functional configurations.In this paper we propose new schemes to package flat and curved membranes of finite thickness by using multiple spirals, whose governing equations render folding lines by juxtaposing spirals and by accommodating membrane thickness. Our experiments using a set of topologically distinct flat and curved membranes deployed by tensile forces applied in the radial and circumferential directions have shown that (1) the multi-spiral approach with prismatic folding lines offered the improved deployment performance, and (2) the deployment of curved surfaces progresses rapidly within a finite load domain. Furthermore, we confirmed the high efficiency of membranes folded by multi-spiral patterns.From viewpoints of configuration and deployment performance, the multi-spiral approach is potential to extend the versatility and maneuverability of spiral folding mechanisms.     

Folding patterns of planar gossamer space structures consisting of membranes and booms

The combination of large membranes and light-weight deployable booms, often called a gossamer structure, has enabled innovative space missions, such as solar sailing, to become possible. Though many designs have been proposed and demonstrated, two problems remain regarding the folding patterns of the membranes. The first problem involves considering the thickness of a membrane to enable uniform and compact folding. The other involves membrane-folding patterns that allow for connecting the membrane to the booms at multiple points and deploying them together while minimizing the use of complex mechanisms. This study proposes three methods that consider the thickness, and two of them can keep the crease lines straight, in contrast to the conventional non-straight crease line solutions. In addition, this study derives one effective design to integrate a membrane with diagonal booms through the systematic classification of existing membrane folding patterns.     

Spinning solar sail orbit steering via spin rate control

The orbit of a solar sail can be controlled by changing the attitude of the spacecraft. In this study, we consider the spinning solar power sail IKAROS (Interplanetary Kite-craft Accelerated by Radiation Of the Sun), which is managed by Japan Aerospace Exploration Agency (JAXA). The IKAROS attitude, i.e., the direction of its spin-axis, is nominally controlled by the rhumb-line control method. By utilizing the solar radiation torque, however, we are able to change the direction of the spin-axis by only controlling its spin rate. With this spin rate control, we can also control indirectly the solar sail’s trajectory. The main objective of this study is to construct the orbit control strategy of the solar sail via the spin-rate control method. We evaluate this strategy in terms of its propellant consumption compared to the rhumb-line control method. Finally, we present the actual flight attitude data of IKAROS and the change of its trajectory.