佐藤 泰貴

第28回アストロダイナミクスシンポジウム (2018年7月30-31日. 宇宙航空研究開発機構宇宙科学研究所), 相模原市, 神奈川県資料番号: SA6000135023レポート番号: A-23

© 2018, American Institute of Aeronautics and Astronautics Inc, AIAA. All rights reserved. An elasto-plastic crease model under deployment is examined to predict the deployment behavior of the membrane accurately. The elasto-plastic deformation properties of the membrane under folding and deployment are identified numerically. The results of the numerical analyses for the creasing process are in good agreement with the experiments, and thus, the elasto-plastic deformation properties of the crease are verified. In consideration of the properties, a numerical model of the crease is proposed to express the elasto-plastic deployment behavior of the crease and to reduce the nodes in the finite element analyses, where rotational spring is employed. Additionally, the results indicate that the spring constant of the crease model at high tensile force does not depend on the layer thickness of the creased configuration.

Copyright © 2018 by the International Astronautical Federation (IAF). All rights reserved. As an innovative spacecraft system, a transformable spacecraft is proposed, which consists of multiple bodies connected with each other. They are equipped with actuators that move them relatively within a certain range of angle. The shape of the bodies is arbitrary, and the simplest is panel shape, for example. Supposing a transformable spacecraft consisting of a number of panels, they can be folded to be compact as a whole, unfolded to configure a large plane, and recomposed to configure various kinds of three-dimensional shape. The system enables a single spacecraft to have multiple functions by transforming the shape. A distinctive characteristic of a transformable spacecraft is its capability of performing nonholonomic attitude control. By transforming to another shape and transforming back to the original shape in a different path, the attitude is changed even if the shape is unaltered. This nonholonomic control is realized only by internal torque, and does not require any fuel consumption. We introduce the concept of a transformable spacecraft and its applications to missions, utilizing the nonholonomic control. For example, combining the function of variable-shape structure with the nonholonomic control, a multifunction space telescope can be realized orbiting around the Sun-Earth Lagrange point.

© 2017, American Institute of Aeronautics and Astronautics Inc, AIAA. All rights reserved. A spinning solar sail membrane with 14 meters in width and 7.5 microns in thickness of small solar power sail demonstration spacecraft “IKAROS” was deployed in space in 2010. After the deployment, images of the membrane taken by separation cameras and onboard cameras revealed that the sail membrane might be deformed toward the sun against the solar radiation pressure and that the membrane kept its deployed shape even under very low spin rate. In order to investigate the mechanism of the phenomena, the authors have performed detailed numerical investigations of the structure characteristics of the deployed sail employing the nonlinear finite element analysis software Abaqus. In the previous paper, it was reported that the curvatures of thin film solar cells attached to the sail might increase the stiffness of the membrane by conducting a static implicit analysis of Abaqus.1 In this paper, a new finite element model of the sail membrane is created and dynamic explicit analysis of Abaqus is employed to decrease the calculation time. Deployed shape analyses under several combinations of the curvatures and spin rates are conducted and the results which indicate upward deformation and high stiffness are obtained. Finally, geometric mechanism of the deployed shapes of the spinning square sail is discussed.

Copyright © (2017) by International Astronautical Federation. All rights reserved. A mechanism for the high-precision positioning of reflector segments by using kinematic couplings has been developed for balloon-borne radio telescopes, and the effectiveness of the mechanism is demonstrated through experiments. A high-precision reflector for radio telescopes is under development, and it is intended to be used for the observation of radio waves of up to 300 GHz. The reflector consists of six segments, a back structure, and a high-precision positioning mechanism. The high-precision positioning mechanism utilizes kinematic couplings, and the segments are positioned and fixed precisely to the back structure by the kinematic couplings. The positioning of the segments on the back structure is one of the largest sources of error in reflector systems. Therefore, kinematic couplings are important components of a reflector system for achieving a high surface accuracy. Three combinations of a ball and a V-groove are employed in the positioning mechanism. Load-applying mechanisms are used to apply and control pressing loads between the segment and back structure. In order to demonstrate the effectiveness of the mechanism, the positioning repeatability between a segment and a back structure was investigated through experiments. In these experiments, the reflector segment was attached to and detached from the back structure, and the relative positions of the reflector with respect to the back structure were measured using a photogrammetry system during the process of attachment. The cycle of attachment, measurement, and detachment was repeated five times, and the positioning repeatability was evaluated. A positioning accuracy of approximately 20 um RMS was achieved using the developed reflector system. The results demonstrate the effectiveness of the positioning mechanism, which incorporates kinematic couplings for the high-precision positioning of a reflector for a balloon-borne radio telescope.

© 2016, American Institute of Aeronautics and Astronautics Inc, AIAA. All rights reserved. Many de-orbiting systems using deployable membranes are developed to keep the safety space environment. We have proposed a boom-membrane integrated space structure using tri-axial tubular CFRP booms. This paper describes detailed properties of the booms with and without the gravity compensation devices and fixed and free for rotation constraint of the stowage hub through the deployment experiments. We focus on the boom tip because the point where the membrane is applied by the tensile forces. In the experiments we measure the tip position and calculate the time history of deploying length and tip speed. As a result, the effects of the gravity compensation devices and rotation constraint of the stowage hub to deployment of the booms are clarified, as well as the validity of the hinge deployment model has been verified.

© 2015, American Institute of Aeronautics and Astronautics Inc. All rights reserved. This paper discusses the deformation properties of the solar sail IKAROS membrane to identify the possible causes of the phenomena observed by the flight data: the direction of the out-of-plane deformation. The flight data indicated that the direction of the out-of-plane deformation of the sail membrane was toward the Sun, although the solar pressure was applied from the Sun. This study hypothesized that the possible causes of the phenomenon is due to the initial curvature of the thin film devices on the sail and due to the circumferential slack induced by the bridges which connects each trapezoidal petal. The hypothesis was verified through geometrically nonlinear finite element analyses. The analysis results indicated that the sail membrane could deform in the Sun’s direction when the initial curvature of the thin film devices and the circumferential slack were simultaneously applied.

© 2015, American Institute of Aeronautics and Astronautics Inc. All rights reserved. The membrane-boom deployable structures which consist of self-deployable tri-axis CFRP boom with skew/spiral fold membrane wrapped around a single hub, have been developing for several small satellite missions as, solar sails, de-orbiting membrane systems, thin solar cell deployable membranes, and membrane antennas. Because the deployment properties of the membrane-boom structures depend on the self-deploying properties of the CFRP booms, the integration of membrane and booms is significant for designing the deployable structures. Also, the deploy-ability of the membrane-boom structures has to be evaluated by the ground testing and numerical simulations. This paper focuses on the dynamic properties of the membrane-boom deployable structures in the course of deployment through deployment experiments. Experimental results of the membrane-boom deployable structures models indicated the dynamic properties of membrane-boom deployable structures and non-linear buckling like properties for the deployable booms are discussed as well as to realize the simultaneous fold and deployment with simple holding/deploying mechanisms.

This paper addresses a simultaneous design optimization of the structure and actuator location for a plate model of space antenna to realize the high precision surface. The space antenna has an adaptive structure system to correct multiple surface error modes, which are induced in the space environment. The design optimization for the correction of the multiple surface error modes is formulated, where the weighting residual surface error vector is introduced to evaluate the contribution of the error modes. A constraint parameter of the actuator location is proposed to improve the performance of the design optimization. The results of the design optimization indicate that high performance is obtained by using the proposed constraint parameter, and thus, the effectiveness of the proposed parameter is verified.

This paper addresses the deformation properties of the IKAROS membrane to identify the IKAROS' higher out-of-plane stiffness, which was higher than expected. IKAROS' flight data showed that the out-of-plane deformation of the membrane was smaller than that predicted preflight by numerical simulations. A possible cause is the initial deformation of the IKAROS membrane, which is induced by the initial curvature of the thin film solar cells and the reflection control devices. In order to examine the effects of the initial deformation on the out-of-plane stiffness, nonlinear finite element analyses were carried out with shell elements for the 1/4 IKAROS membrane using the initial curvatures of the thin-film components. The results of the numerical simulations indicated that the on-orbit IKAROS membrane was nonflat due to the initial curvature of the thin-film components. The out-of-plane deformation with the initial deformation was found to be smaller than the deformation of the ideal flat membrane, and the numerical results qualitatively agreed with the IKAROS' flight data. As the initially deformed membrane increases the out-of-plane stiffness, which determines the deformation properties of the membrane, the bending stiffness is significant for the simulation of nonflat membrane structures. Based on the results, the mechanics of the higher out-of-plane stiffness of the IKAROS membrane was identified: it is the effects of the initial deformation of the membrane, which is globally propagated by the local deformation of initial curvatures of the thin film components.

Copyright ©2014 by the International Astronautical Federation. All rights reserved. The membrane-boom deployable structures which consist of self-deployable tri-axis CFRP boom with skew/spiral fold membrane wrapped around a single hub, have been developing for several small satellite missions as, solar sails, de-orbiting membrane systems, thin solar cell deployable membranes, and membrane antennas. Because the deployment properties of the membrane-boom structures depend on the self-deploying properties of the CFRP booms, the integration of membrane and booms is significant for designing the deployable structures. Also, the deploy-ability of the membrane-boom structures has to be evaluated by the ground testing and numerical simulations. This paper focuses on the dynamic properties of the membrane-boom deployable structures in the course of deployment through deployment experiments. Experimental results of the membrane-boom deployable structures models indicated the dynamic properties of membrane-boom deployable structures and non-linear buckling like properties for the deployable booms are discussed as well as to realize the simultaneous fold and deployment with simple holding/deploying mechanisms.

第29回宇宙構造・材料シンポジウム（2013年12月3日. 宇宙航空研究開発機構宇宙科学研究所 (JAXA)(ISAS)), 相模原市, 神奈川県資料番号: SA6000013001レポート番号: A1