佐藤 泰貴

大気球シンポジウム 2021年度（2021年11月1-2日. オンライン開催)資料番号: SA6000166007レポート番号: isas21-sbs-007

The Martian Moons Exploration (MMX) mission of the Japan Aerospace Exploration Agency (JAXA) is scheduled to launch in 2024 and aims to be the world's first mission to return a sample from Phobos. For this, JAXA is developing the MMX sampler. There is a special interest in developing the corer shooting mechanism (C-Sampler) to acquire regolith, a robotic arm to position the core sampler and transfer the acquired regolith, and a sample transfer mechanism to move the regolith to a sample return capsule. This paper reports the system design of the MMX Sampler as well as the results of the tests for the corer sampling mechanism and the regolith conditions needed for effective penetration.

第3回観測ロケットシンポジウム（2021年3月24-25日. オンライン開催)著者人数: 14名資料番号: SA6000162017レポート番号: Ⅴ-3

© 2021, American Institute of Aeronautics and Astronautics Inc, AIAA. All rights reserved. A novel approach for shape control of membrane structures is presented. The shape control is accomplished by exciting a spinning membrane. The membrane forms a shape consisting of several vibration modes, depending on the input frequency, and the wave surface stands still when its frequency is synchronized with the spin; that is, the wave propagation and the spin cancel each other, resulting in a static wave surface in the inertial frame. This paper describes the general theory of the static wave-based shape control. The mathematical model of membrane vibration, classification of control input, and the control system for exciting a static wave are summarized. The proposed method is demonstrated through a ground experiment. A 1 m large polyimide film is rotated and is vibrated in a vacuum chamber, and the output shape is measured using a real-time depth sensor. The nonlinear dynamics of membrane deformation under both the ground and space environments is simulated using a numerical method, showing the validity and effectiveness of the shape control method.

A Pneumatic Sampler (P-SMP) is being provided by Honeybee Robotics with support from NASA Planetary Missions Program Office (PMPO) for JAXA’s Martian Moons eXploration (MMX) mission. The goal of this mission is to closely survey the Martian moons Deimos and Phobos, and then to collect regolith from Phobos and return it to Earth. The P-SMP will be mounted to a leg of the lander and will be responsible for collecting surface regolith alongside the JAXA provide Core Sampler (C-SMP). The Sampling Funnel of the P-SMP 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 for Earth return. Several iterations of the P-Sampler have been designed and tested inside a vacuum chamber with Phobos regolith simulant. In all tests, the P-Sampler successfully acquired the sample, even in an extreme scenario where the sampling head was mounted 10 cm above a surface covered with gravel.

This paper presents a novel approach to sampling subsurface asteroidal regolith under severe time constraints. Sampling operations that must be completed within a few hours require techniques that can manage subsurface obstructions that may be encountered. The large uncertainties due to our lack of knowledge of regolith properties also make sampling difficult. To aid in managing these challenges, machine learning-based detection methods using tactile feedback can detect the presence of rocks deeper than the length of the probe, ensuring reliable sampling in unobstructed areas. In addition, given the variability of soil hardness and the short time available, a corer shooting mechanism has been developed that uses a special shape-memory alloy to collect regolith in about a minute. Experiments on subsurface obstacle detection and shooting-corer ejection tests were conducted to demonstrate the functionality of this approach.

© 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 by the International Astronautical Federation (IAF). All rights reserved. A solar sail is not only propelled by solar radiation pressure (SRP), but also generates torque using SRP. When a sail membrane's shape is not flat, unexpected torque due to SRP is generated. It is necessary to control the sail membrane's shape and the resulting SRP torque to operate a solar sail for long periods and to reduce fuel consumption. Membrane shape control is a common issue not only in solar sails but also in space membrane structures. Therefore, we propose a method to actively control the in-plane and out-of-plane torque by deformation of the membrane shape using Shape Memory Alloy wires (SMA wires). An SMA wire is a type of a soft actuator that contracts when heated. In the proposed method, the SMA wires are attached at several locations on the sail membrane, allowing the entire membrane to deform in out-of-plane at the locations where the SMA wires contract. Furthermore, it is possible to control the membrane shape depending on the situation by selectively contracting subsets of SMA wires. In this paper, a finite element analysis and an experiment were conducted under the same condition to validate the numerical modeling for the SMA wire actuation. As a result, the validity of the membrane shape analysis could be shown since the tendency of the membrane shape deformation was the same in the experiment and the analysis. Next, the relationship between the SMA wire positions and the resulting SRP torque is clarified via another numerical analysis. Results show that in-plane and out-of-plane torques can be produced, respectively by contracting the SMA wires in line-symmetric and point-symmetric manners.

Transformable spacecraft under development is an innovative system that consists of several structural components, such as panels, connected together by internal force actuators. The spacecraft can change its structure drastically by driving installed actuators and achieve the following four features simultaneously. The first feature is "attitude change by internal force using non-holonomic characteristic of the system". It is possible to orient the spacecraft to an arbitrary direction by repeating the deployment of the panel in an appropriate order by the internal force actuator. The second feature is that "change of the structure enables the multiple functions by switching modes". Two telescopes will be installed for scientific missions utilizing the features of the transformable spacecraft and used to realize two different observation modes. One is a mode in which each telescope is oriented to different directions to perform wide-field observation (single telescope mode). The other is a mode in which two telescopes are pointed in the same direction. This mode enables the spacecraft to work as an interferometer (interferometer mode). The third feature is "orbit control and orbit keeping by controlling the solar radiation pressure on the spacecraft with the use of change of spacecraft structure". Since the spacecraft can change its structure by the internal force actuator, the orbit control and orbit keeping are achieved without fuel consumption. By utilizing this feature, the spacecraft will be injected into an artificial halo orbit around Sun-Earth Lagrangian point L2, and the technology demonstration of the transformable spacecraft and the observation mission will be performed in the orbit. The fourth feature is "passive cooling of observation equipment by use of panels as sunlight shield". In the observation mode, observation in the infrared region is performed and sufficient cooling is required. Appropriate arrangement of panels enables shielding of sunlight, and then the passive cooling of the observation equipment is realized. As a result, disturbance due to refrigerator is eliminated, which contributes to precise observation in addition to the contribution by non-holonomic attitude control without disturbance. This paper shows the analysis and experimental results for feasibility studies and conceptual designs of above four features. Furthermore, development status of the system and each subsystem to realize the spacecraft are introduced.

Martian Moons eXploration (MMX) is a mission to Martian moons under development in JAXA with international partners to be launched in 2024. This paper introduces the system definition and the latest status of MMX program. “How was water delivered to rocky planets and enabled the habitability of the solar system?” This is the key question to which MMX is going to answer in the context of our minor body exploration strategy preceded by Hayabusa and Hayabusa2. Solar system formation theories suggest that small bodies as comets and asteroids were delivery capsules of water, volatiles, organic compounds etc. from outside of the snow line to entitle the rocky planet region to be habitable. Mars was at the gateway position to witness the process, which naturally leads us to explore two Martian moons, Phobos and Deimos, to answer to the key question. The goal of MMX is to reveal the origin of the Martian moons, and then to make a progress in our understanding of planetary system formation and of primordial material transport around the border between the inner- and the outer-part of the early solar system. The mission is to survey two Martian moons, and return samples from one of them, Phobos. In view of the launch in 2024, the phase-A study was completed in February, 2020. The mission definition, mission scenario, system definition, critical technologies and programmatic framework are introduced int this paper.

© 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.

Solar power sail technique was demonstrated in the IKAROS mission. However, unexpected phenomena were confirmed. The membrane surface of IKAROS has deformed to a shape that was not flat. In the shape change of the film surface, it is known that the whole membrane surface changes greatly like an umbrella shape or a saddle shape depending on the warping direction of the thin film solar cell. Objection of this study is to clarify mechanism of influence on solar radiation pressure torque due to warp of membrane device and its solution method. Therefore, the shape of the overall membrane surface is clarified by using a simple FEM model and the SRP torque with respect to the shape is calculated, and the mechanism of the overall shape change in warpage and its influence is clarified. As a result, the influence on SRP is related to membrane surface stiffness and warped direction and it was found that it is best that the membrane is warped in the radial direction and its outermost stiffness is high.

In recent years, a large space film structure having a thickness of several micro and a shape of several to several tens of meters attracts attention, and various storing methods have been studied. Considering the thickness of the film surface at the time of winding before launching, there is a problem that circumferential difference occurs inside and outside of the folded film surface. In order to solve this problem, a method of solving the difference between the inner and outer circumference by predicting the inner / outer circumferential difference arising from the film surface and the thickness of the device and managing the phase has been proposed. On the other hand, the point that the target value for adjusting the phase is unknown and empirical was pointed out, and as a result of adjusting the phase, the wave-like slack that occurred caused the unevenness of the film thickness in the circumferential direction. In this research, we derive target value of phase management analytically, compare with experiment, and verify.

Copyright © 2019 by the International Astronautical Federation (IAF). All rights reserved. In this study, we modify multi-particle method, a calculation method for predicting membrane behaviour, for evaluating collision between membranes and the change in membrane compression and bending stiffness due to devices mounted on membrane. This modification is verified its validity by the consistency with the results of the experiments conducted in the previous study. Then, we investigate the changes in the deployment behaviour when the temperature and thickness of solar cells change.

Copyright © 2019 by the International Astronautical Federation (IAF). All rights reserved. Martian Moons eXploration (MMX) is a mission to Martian moons under study in JAXA with international partners to be launched in 2024. This paper introduces the mission definition and the latest status of MMX program. “How was water delivered to rocky planets and enabled the habitability of the solar system?” This is the key question to which MMX is going to answer in the context of our minor body exploration strategy preceded by Hayabusa and Hayabusa2. Solar system formation theories suggest that small bodies as comets and asteroids were delivery capsules of water, volatiles, organic compounds etc. from outside the snow line to entitle the rocky planet region to be habitable. Mars was at the gateway position to witness the process, which naturally leads us to explore two Martian moons, Phobos and Deimos, to answer to the key question. The goal of MMX is to reveal the origin of the Martian moons, and then to make a progress in our understanding of planetary system formation and of primordial material transport around the border between the inner- and the outer-part of the early solar system. The mission is to survey two Martian moons, and return samples from one of them. In view of the launch in 2024, the phase-A study is to be completed in this year. The mission definition, mission scenario, system description, and programmatic framework are introduced int this paper.

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