大槻 真嗣

平成30年度宇宙科学に関する室内実験シンポジウム (2019年2月28日-3月1日. 宇宙航空研究開発機構宇宙科学研究所(JAXA)(ISAS)相模原キャンパス), 相模原市, 神奈川県資料番号: SA6000139027

© 2019 by the American Institute of Aeronautics and Astronautics, Inc. All rights reserved. Fuel sloshing shows a non-linear response under microgravity conditions, so it becomes difficult to predict the liquid motion and the dynamic force acting on the tank walls. During the touchdown phase of landers, it is necessary to quantitatively evaluate the effect of sloshing to avoid the turnover of landers. In the present paper, microgravity experiments using parabolic flights were conducted. The dynamic liquid motion in a spherical tank subjected to a vertical impulsive acceleration was successfully visualized. The numerical simulation corresponding to the experiment was also carried out and the computed liquid motion showed a good agreement with the experimental results. As the application of this numerical method, the dynamic response of sloshing during the touchdown phase of the Marian Moons eXploration (MMX) lander was discussed. It was revealed that the liquid column rose after the landing, and the upward force acted on the landers several times with time delay. Moreover, the effectiveness of ring baffle plate as a damping device was successfully confirmed.

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.

The world's smallest moon lander (OMOTENASHI) will be launched by NASA's space launch system. The lander impacts to the moon at 100km/h. The landing impact is absorbed by crushable materials and an airbag consisted of an external cover and an air chamber made by polyimide films. However, the coexistence of tough glued strength and lightweight will not be expected. Meanwhile, welding technique for polyimide films has been proposed which can be fabricated stronger and lighter than the glued films. In this paper, the development of the air chamber fabricated by using the welding technique for polyimide films is shown.

DESTINY+ is a flyby space mission for the asteroid named Phaethon and will be launched in 2022. Camera system in Flyby space mission has been conventionally controlled by a PD controller. However, PD controller cannot generally consider constraints. A flyby mission requires a robust control for constraints in traversing at high-speed. This paper proposes a control scheme based on Model predictive Control for a flyby mission with robustness for constraints of input and angular velocity. The simulation study shows that Model predictive Control is effective for robustness in a flyby mission.

When the lander carries a large amount of fuel, the landing on a celestial body becomes difficult and dangerous due to sloshing of fuel. Sloshing of fuel causes turbulence of attitude and overturning of the lander. In order to design a landing gear and attitude control system, landing simulation with a sloshing will be required. The mechanical sloshing model that takes the place of experiment and computational fluid dynamics is required for the landing simulator. This paper describes the modelling of mechanical concentrated-constant sloshing models for a landing simulator and the result of numerical simulations of landing on a small body celestial bodies.

Understanding the interaction between granular materials on surface of a small body and a spacecraft is the key issue to design equipments of the spacecraft utilized in a future planetary exploration. Aiming to realize a safe long-term stay on the small body, this paper presents the experimental results that acquired the basic data about the interaction through the drop tower test.

© ICROS. Model Predictive Control (MPC) is one of control methods for the discrete time system. The optimum input is calculated by using Linear Quadratic Regulator (LQR). In MPC, the cross-product term is generally omitted in the evaluation function for LQR. However, the effectiveness of the cross-product term for LQR is confirmed by various researches. Therefore, this paper addresses the expanded form of cross-product term applied to MPC. Simulation of zero momentum spacecraft shows that the cross-product term is effective for consideration of performance to MPC.

This paper presents a novel mechanical design for efficient traverse of hopping rovers. In order to continue the exploration of planetary environment without any human help, optimizations and efficient designs of rovers are essential. In particular, improving robustness and decreasing energy consumption are crucial aspects of rovers design. Hopping efficiency on sandy surfaces is strikingly worse than on hard ground, because such soil is deformed and easily causes slip. The purpose of this paper is to develop a novel mechanical design which can get enough friction from granular media. First, the effects of soft soil for hopping are studied by comparing with hopping on hard ground in terms of energy. Next, a novel foot pad design for hopping on planetary terrain is proposed. Inspired by the conventional wheeled vehicle design, treads, called grouser, are installed for the bottom of the proposed foot pad. The effectiveness of the proposed design is validated through experimental evaluation.

Planetary exploration rovers face severe energy and safety restrictions, which have a strong connection with terrain slopes. During a steep slope traverse, a rover consumes more power and is exposed to higher risks of getting stuck or of overturning. It is essential for a rover to autonomously recognize and avoid steep slopes for efficient and safe operations. Existing techniques (e.g. stereo vision) do not completely address challenges in planetary exploration, such as low-textured terrain appearance and computational resource limitations. This paper presents a novel slope estimation method using a monocular infrared camera. The proposed method estimates slope normals based on surface temperatures on two different slopes. The surface energy model is employed to correlate thermal properties to geometrical properties of the terrain. The idea behind this approach is that the solar radiation, which is a major energy source for terrains, can differ by time, slope angles and directions. The difference in energy input generates the gap of surface temperatures between target and reference surfaces, which can be remotely detected with an infrared camera. The proposed method avoids the problem of terrain appearance as it only uses temperature measurements, and is also computationally efficient thanks to efficient preprocessing. The algorithm is validated through simulations and outdoor experiments. The results show the effectiveness of the proposed scheme to estimate terrain slope normals solely from temperature measurements.

Hopping rover is one of solution for locomotion on loose and rocky terrain on the moon and planetary surface. The hopping rover jumps over an obstacles. Since the height of hopping is equal to the height which the rover can get over, the traversability of rover becomes higher. In order to design a push plate with a small amount of slip on the granular media for a stable and efficient hopping, it is necessary to know the reaction force received from the ground. In this paper, we describe the force estimation method of shoe plate design of jump rover based on Resistive Force Theory and calculate the reaction force when pressing the shoe plate and find of the shape that is suitable for hopping. The shoe plate is manufactured with a 3D printer, and the pressing test result and the calculation result are compared. Finally, we verify the effectiveness including the hopping motion of the rover, using the dynamics simulator on the moon gravity.

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.

Model Predictive Control (MPC) is one of control methods for the discrete time system. The optimum input is calculated by using Linear Quadratic Regulator (LQR). In MPC, the cross-product term is generally omitted in the evaluation function for LQR. However, the effectiveness of the cross-product term for LQR is confirmed by various researches. Therefore, this paper addresses the expanded form of cross-product term applied to MPC. Simulation of zero momentum spacecraft shows that the cross-product term is effective for consideration of performance to MPC.

<p>小型月面探査機OMOTENASHIには，月面着陸時に機器の破損を防ぐために衝撃緩和装置としてエアバッグを搭載する．エアバッグ気室はポリイミド製であるが、従来の樹脂製接着剤を用いた製作方法では目標の質量を超えていた．そこで，気室（バルーン）の軽量化を目的とし，本研究室が有しているポリイミド溶着技術の応用によって新たなバルーンの設計・製作を実施した．本発表では製作したバルーンの性能評価及び構造の改良について述べる．</p>