森 治

Copyright ©2014 by the International Astronautical Federation. All rights reserved. Most of space membrane structures have creases on their membranes. The first solar power sail "IKAROS" launched by Japan Aerospace Exploration Agency (JAXA) in 2010 deployed its folded membrane centrifugally by spinning itself. IKAROS has a cylindrical main body at the center and four trapezoidal membranes called petal around the main body. The petals were folded up into concertinas and wrapped round the main body before the deployment. JAXA is currently developing the next-generation solar power sail which has the same structure as IKAROS and a wider membrane than IKAROS. The creases on space membrane structures significantly affect the behavior of its membrane. The creases make the bending or compressive stiffness of the membrane larger. IKAROS could not deploy its petals at the same time because the deployment of a specific petal lagged behind that of the other petals significantly. This deployment behavior is called the asymmetric deployment and was observed by some deployment experiments in a vacuum chamber. The asymmetric deployment might affect success and failure of a mission because the asymmetric deployment confuses the attitude of a spacecraft. The creases are considered a cause of the asymmetric deployment but the factor of the asymmetric deployment has not been clarified yet. Furthermore, previous simulation models do not consider the mechanical characteristic of the creases sufficiently and they have not recreated the asymmetric deployment. Therefore, this work proposes an analysis model of space membrane structures considering mechanical characteristic of creases. This analysis model is modeled by multi-particle method because it is difficult to simulate the dynamic behavior of the membrane by using finite element models due to computational convergent and cost. In the proposed model, the strength of the creases and the bending or compressive stiffness resulting from the creases are simulated by many rotational springs and compressive springs. The spring constants or natural angles are determined by two static experiments under gravity. The proposed model also considers the local buckling on the creases. The deployment experiments in a vacuum chamber were simulated by the proposed model. The simulations successfully recreate the asymmetric deployment and the proposed model is validated. Furthermore, the simulations clarified that the local buckling on the creases affects the behavior of the membrane and the asymmetric deployment. The proposed model and the knowledge obtained by these simulations contribute many missions using space membrane structures like solar sail missions.

This paper gives a detailed evaluation of the solar and thermal radiation accelerations acting on the IKAROS solar sail and its spacecraft body during its operational mission from June to December 2010. In particular, the predicted temperatures are compared with actual in-flight measurements on the sail membrane as well as on the body. The results show fairly good correspondences in most cases but a few appreciable deviations have also been observed. The simulation results indicate that the magnitude of the thermal radiation perturbations on the solar sail trajectory is only about one percent of the solar radiation and may be neglected in view of the considerable uncertainties in the solar radiation force.

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.

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

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: SA6000013003レポート番号: A3

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: SA6000013022レポート番号: B7

The present study proposes ... Features (i) stiffer for ground testing, (ii) Synchronous boom-membrane deployment, (iii) Resist launch vibration, (iv) Repeatable and simpler folding pattern, ... to be written!. Copyright© (2013) by the International Astronautical Federation.

The present study proposes ... Features (i) stiffer for ground testing, (ii) Synchronous boom-membrane deployment, (iii) Resist launch vibration, (iv) Repeatable and simpler folding pattern, ... to be written!. Copyright© (2013) by the International Astronautical Federation.

The present study proposes ... Features (i) stiffer for ground testing, (ii) Synchronous boom-membrane deployment, (iii) Resist launch vibration, (iv) Repeatable and simpler folding pattern, ... to be written!. Copyright© (2013) by the International Astronautical Federation.

This paper describes a basic characteristic of a 7/8-GHz band circular stacked patch active integrated array antenna (AIAA) unit for solar sail embedding application. The proposed AIAA unit mainly consists of a 2×2 stacked circular patch array, two low noise amplifiers (LNAs) and two power amplifiers (PAs). The array has stacked structure for dual band operation. Moreover, the stacked patch array has orthogonal feed structure for better isolation characteristics between transmitter and receiver ports. Radiation patterns and S-parameters are evaluated by 3-D electromagnetic field simulation and measurement. © 2013 IEEE.