佐藤 泰貴

© 2020 IEEE. The goal of the JAXA's Martian Moons Exploration (MMX) mission is to explore the two moons of Mars, Phobos and Deimos, and return samples from the surface of Phobos. Honeybee Robotics is designing and fabricating a NASA-provided Pneumatic Sampler, or P-Sampler, that would capture surface material from Phobos using a pneumatic sampling approach. The P-Sampler will be mounted along a leg of the MMX lander. The sampling head of the P-sampler utilizes two sets of sampling nozzles: one set of nozzles pointed directly at the surface to kick-up and loft material into the sampling head, and a second set of nozzles to direct the oncoming material into the sample return canister further up the lander leg. A robotic arm mounted underneath the lander will then remove the sample canister and place it inside the sample return capsule. Several iterations of the P-Sampler have been designed and tested inside a vacuum chamber with Phobos analog material. In all tests, the P-Sampler successfully acquired sample, even in an extreme scenario where the sampling head was mounted 10 cm above the surface covered with gravel.

© 2020, American Institute of Aeronautics and Astronautics Inc, AIAA. All rights reserved. This paper addresses how to predict the releasing and the deploying behaviors of the creased space membrane accurately. Although conventional study analyzed the released shape of creased membrane considering the elasto-plastic properties, that shape did not agree with the experimental results when the membrane is tightly creased. To examine the released shape of the membrane, at first, creasing and releasing experiments are carried out. The experimental results indicate that the opening angle of the crease increases with increasing elapsed time after releasing due to stress relaxation. The stress relaxation behavior is predicted by FEA considering on the visco-elasto-plastic material properties. In addition, the analytical model of the releasing and the deploying membrane is proposed. The results of the FEA and the analytical model show that the released angles are good agreement with experimental results. Thus, it is found that the effects of the viscosity are important to predict the releasing behavior of the space membrane.

© 2019, Tsinghua University Press. A solar power sail demonstrator “IKAROS” demonstrated solar sailing technology in 2010. The membrane of the spinning solar sail IKAROS is estimated to be deformed toward the Sun. The deformation was kept even under low spin-rate. Previous studies suggest that curvature of thin-film solar cells on the membrane increases the out-of-plane stiffness by finite element analysis. Shape, out-of-plane stiffness, and natural frequency of membranes have to be predicted for solar sails with thin-film devices, such as thin-film solar cells, dust counters, and reflectivity control devices in order to reduce the margins of sail size and propellant mass against disturbance solar pressure torque acting on the membrane. In this paper, the effect of a curved thin-film device on the natural frequency of a rectangle membrane under uniaxial tension was investigated. Three types of membranes were evaluated: a membrane with a curved thin-film device, a membrane with a flat thin-film device, and a plane membrane. Geometric nonlinear finite element analysis and eigenvalue analysis were conducted to investigate the natural frequencies under varying tension. The simulations were verified by vibration experiments. It was found that under low tension, the natural frequency of the membrane with the curved thin-film device is significantly higher than that of the others and that under high tension, the natural frequency of the membrane with the thin-film device is slightly lower than that of the plane membrane. In addition, parametric analysis on the curvature of the thin-film device shows that natural frequency at low tension is sensitive to the curvature. The eigenvalue analysis of a whole solar sail with the curved thin-film devices also suggests that the curvature remarkably affects the vibration modes. In conclusion, curved thin-film devices have a significant impact on the out-of-plane stiffness of a membrane under low tension.

Copyright © 2019 by the International Astronautical Federation (IAF). All rights reserved. In recent times, a variety of small satellite missions use a space membrane structure for a large solar cell or a deorbit device. These devices require attitude meneuver of the membrane. Some of past missions change the attitude of the membrane as the attitude maneuver of the satellite. The other missions use RCDs to change the attitude. While these methods can achieve attitude maneuver, they cannot achieve both agility and vibration attenuation of the membrane. This study proposes an attitude control method of the membrane with electromagnetic force. This method attaches a loop of electrical wire on the membrane edge, and the electromagnetic force caused by the interaction between the current and magnetic field changes the attitude and attenuates the vibration of the membrane. The aim of this study is to evaluate the agility and the vibration attenuation function of the proposed method with numerical simulation. In this study, the attitude dynamics of the satellite and the movement of the membrane is modelled with unconstrained model, and PD control is used. The numerical simulation results are shown in this study, and it is revealed that the proposed method can achieve agile attitude control. However, membrane attenuation does not work well, and thus, this study provides the correction point.

© 2019, American Institute of Aeronautics and Astronautics Inc, AIAA. All rights reserved. This paper addresses how to design bonding area of the thin-film solar cell attached large space membrane structure. The solar cell glued membrane is easily deformed by the temperature change because of the thermal expansion mismatch between the solar cell the adhesive layer which decreases the power generation efficiency of the solar cell. On the other hand enough bonding area is required to have enough strength under deployment load condition. Thus an optimum bonding area design is examined by using FEA for a single unit of solar cell for OKEANOS membrane. The results of the analyses indicate that the above requirements can be satisfied by employing discreetly located bonding area with having curvature directionality. The obtained design is applied to the OKEANOS membrane where the deformed shape of the membrane with curved solar cell is obtained by FEA. As the results the membrane shape satisfies the requirements thus the effectiveness of the bonding area design is indicated.

第34回宇宙構造・材料シンポジウム（2018年12月4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: SA6000137042レポート番号: B20

第34回宇宙構造・材料シンポジウム（2018年12月4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: SA6000137041レポート番号: B19

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: SA6000135019レポート番号: A-19

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.