In-Plane/Out-of-Plane Librations of a Tethered System in Elliptic Orbits

In-plane/out-of-plane librations of a tethered system in elliptical orbits are investigated. It is aimed to clarify the fundamental characteristics of libration of the tethered system subjected to orbital motion and atmospheric drag. Periodic solutions and their stability of a simplified 3-DOF model are analyzed, in which in-plane/out-of-plane librations and longitudinal elongation of the tether are considered. It is shown that the librations become asymptotically stable or unstable because of atmospheric drag. The effects of system parameters on stability are analyzed, and it is shown that the property of longitudinal elongation of the tether determines the nature of stability, that is, asymptotically stable or unstable. It is also shown that the property of atmospheric drag determines only the degree of stability. Results of direct numerical simulations show the validity of the results of stability analyses. Physical interpretation of the phenomena is also clearly shown

Development of a Multifunctional Lightweight Membrane with a High Specific Power Generation Capacity

As a lighter power generation system, Japan Aerospace Exploration Agency (JAXA) and Sakase Adtech Corp. are developing a demonstrator component named “Harvesting Energy with Lightweight Integrated Origami Structure” (HELIOS), which is a deployable lightweight membrane structure. HELIOS has solar arrays on its surface and demonstrates the technology which enables higher specific power generation capacity compared to the conventional solar array panels. The membrane also has communication antennas, showing the potency of lightweight membrane’s multifunctionality such as large data transmitting by 5G antennas and high-resolution observation by interferometer antennas. This paper presents the component’s concept and design, and the expected achievements

Enhancement of a Spring-mass System Model for Numerical Simulations of Centrifugal Deployment Dynamics of Folded Square Membranes

In this paper, the spring-mass system model developed for simple numerical simulations of thin membranes is enhanced by taking into account the properties of buckling and creases. The model is applied to the numerical simulations of centrifugal deployments of folded square membranes that are small-scale models for solar sail spacecraft “IKAROS”. First the folding and deployment methods are reviewed. Then the formulation of the enhanced spring-mass system model is explained. Numerical simulations of the centrifugal deployments of two kinds of folded square membranes with different crease intervals are performed and the numerical results are compared with the corresponding experimental results. The deployment behaviors are discussed and the validity of the spring-mass system model is examined

Numerical Simulation of Stepwise Deployment of Membrane Structure with Booms Using Multi-Particle Approximation Method

Deployable membrane structures are hopeful to develop future lightweight large space structures. In order to predict the dynamic behaviors of the structures in the preliminary design phase, simple and fast numerical simulation is necessary. For this purpose, multi-particle approximation method has been studied which models membranes with spring-mass-damper systems. In this study, polygonal membrane structures integrated with extendible booms are investigated. The membranes are deployed by the elasticity of the booms in a stepwise manner. A multi-particle model for one-dimensional elastic body is introduced as the boom model to the multi-particle method. Each boom is released from the tip end by several particles and the dynamic behaviors of the stepwise deployment can be obtained. The behaviors are compared with deployment experiments of booms without a membrane. Numerical simulation of the deployment of a hexagonal membrane with booms is also demonstrated. Finally, the effect of the stepwise pattern on the vibration motion of the central body due to deployment is studied

Wrinkling of a Membrane with a Curved Small Thin Film

In the operation of a solar power sail IKAROS, curved thin-film solar cells were assumed to make the membrane deformed. The deformation caused propellant consumption to counteract windmill torque. For a next solar power sail in the Japan Aerospace Exploration Agency, we conducted experiments and finite element simulations of a simplified model of a part of the solar power sail to understand the effect of a small curved thin-film on wrinkles in a thin membrane under uniaxial tension force. We compared shapes of the membrane with the curved thin-film solar cell under varying tension force. Main findings are that wrinkle lines near both lateral sides of a small curved thin film are bended by curvature of the film and occur under varying tension force