Award type：Award from Japanese society, conference, symposium, etc.  Country：Japan

Country：Japan

Country：Japan

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.2514/1.C036649

Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1016/j.actaastro.2022.06.009

DOI： 10.1016/j.actaastro.2022.06.009

Web of Science

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1016/j.asr.2022.02.050

Web of Science

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：Institute of Electrical and Electronics Engineers (IEEE)  

DOI： 10.1109/ACCESS.2021.3139156

Web of Science

Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (international conference proceedings)  

Web of Science

Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：Japan UAS Industrial Development Association  

Vertical autorotation is proposed and investigated as an emergency landing technique for a multirotor drone suffering a total loss of one motor. A quadrotor with collective pitch control mechanisms is assumed. The blades have no twist because the rotors operate in windmill and propeller modes. The vertical autorotation consists of two phases. In phase 1, all rotors operate in windmill mode and the collective pitch for no attitude control is determined so as to minimize the terminal descending velocity. The quadrotor attitude in phase 1 is adjusted by varying the collective pitch. Flight control in this phase will be a research theme in future. In phase 2, two rotors, including a damaged one, operate in windmill mode while the other two operate in propeller mode. The collective pitch is determined so that the terminal descending velocity at landing is close to 0. Each multirotor has a particular critical altitude value, which relates to the specifics of this vertical autorotation. Critical altitude is the altitude for the case in which phases 1 and 2 are switched just when the descending velocity converges to the terminal velocity during phase 1. The detailed autorotation process depends on the magnitude relationship between the quadrotorʼs critical and initial altitudes.

DOI： 10.34590/tjam.3.7_91

CiNii Research

Language：English   Publishing type：Research paper (scientific journal)  

This paper aims to investigate the ballistic kinetic impactor (B-KI) in order to mitigate the risks posed by a potential asteroid collision on Earth in the future.
The B-KI is a spacecraft that employs a single impulsive thrust to put the spacecraft into an orbit, which, in turn, impacts the target asteroid to deflect it from the collision route of Earth.
To evaluate the effectiveness of the B-KI, we introduce impact-geometry maps (IGMs), which visualize the achievable change in the orbital energy of the asteroid as a function of the spacecraft's semi-major axis and eccentricity. The achievable performance of the B-KI is investigated in the form of its mobility capability on the IGM.
In addition, parameters that govern the mission's feasibility, such as the spacecraft's relative impact speed and phase angle, are discussed.
We conducted a parametric study on the asteroid's orbital elements and found that the B-KI is, in fact, a better option for deflecting asteroids belonging to the Aten family at the intersection point where the radial velocity component is positive.
We also designed several fictional B-KI missions to achieve a more realistic asteroid mitigation campaign scenario.
The obtained results are compared with those of previous kinetic impactor studies that employ low-continuous-propulsion systems.
The study finally highlights that the B-KI can efficiently increase the impact efficiency and deflection distance for a part of the target asteroids.

DOI： 10.1016/j.actaastro.2021.01.027

Web of Science

Language：English   Publishing type：Research paper (scientific journal)   Publisher：American Institute of Aeronautics and Astronautics (AIAA)  

DOI： 10.2514/1.A34817

Web of Science

Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：THE JAPAN SOCIETY FOR AERONAUTICAL AND SPACE SCIENCES  

<p>A small airplane is strongly affected by crosswind in take-off and landing phases, because the flight velocity and gravitational force acting on it are not much larger than the crosswind velocity and aerodynamic force due to crosswind, respectively. A vertical tail volume can be decreased dramatically for a smaller airplane for the stability of lateral/directional motions. The NDD (Neutral Dihedral effect and Directional stability) airplane defined as <i>C</i>_{l_β} = <i>C</i>_{n_β} = 0 was conceived so that it has a tolerance to crosswind. An airplane without a dihedral effect and directional stability is not accepted in the current regulation for airplane design. Then, an airplane with small values of <i>C</i>_{l_β} and <i>C</i>_{n_β} has been newly proposed. All of the modes in the lateral/directional motions can converge without oscillating in the proposed airplane, named ``QNDD'' airplane, which is not observed in the NDD airplane. </p>

DOI： 10.2322/jjsass.69.24

CiNii Research

Language：English   Publishing type：Research paper (scientific journal)   Publisher：THE JAPAN SOCIETY FOR AERONAUTICAL AND SPACE SCIENCES  

<p>Two types of wing geometries imitating wings of birds in gliding flight are analyzed with the vortex lattice method in terms of lift-drag ratio and root bending moment while varying the joint positions and joint angles under the constant lift coefficient and constant flight velocity conditions. One geometry is, what is sometimes called, a gull wing which has a dihedral inner wing and horizontal outer wing, named “DH wing.” On the contrary, the other geometry is a drooped wing which has a horizontal inner wing and anhedral outer wing, named “HA wing.” The lift-drag ratio of the HA wing becomes larger when the joint of the anhedral outer wing is closer to the wing tip with a larger anhedral angle, while the root bending moment of the HA wing becomes smaller when the joint of the anhedral outer wing is closer to the wing root with a larger anhedral angle. In contrast, the DH wing has no combination of a joint position and joint angle to improve the lift-drag ratio, and it is found that the HA wing effectively contributes to the reduction of the root bending moment and the lift-drag ratio compared with the DH wing.</p>

DOI： 10.2322/tjsass.64.267

Web of Science

CiNii Research

Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：The Robotics Society of Japan  

<p>The following three points have been investigated for improving the flight performance of a multiple rotor drone. The first one is `collective pitch control', which enables rotors to change the thrust much quicker than the rotor speed control method．Furthermore, a negative thrust can be generated by the rotors with a negative collective pitch. The negative thrust can cause a large control moment for controlling the attitude. Then, the drone has high maneuverability thanks to the quick thrust change due to the collective pitch control. The second one is `decreases of the moments of inertia', which can enhance the maneuverability of the drone. The variation of moments of inertia has also possibility to decrease a motion of the drone due to a disturbance moment when a feedback control is adopted. The third one is `a rotor with small aspect ratio rotor blades', which generates a larger thrust caused by the larger chord length and the larger thrust coefficient. </p>

DOI： 10.7210/jrsj.39.357

CiNii Research

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.2514/1.G004867

Web of Science

J-GLOBAL

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1016/j.actaastro.2019.10.001

Web of Science

J-GLOBAL

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1109/ACCESS.2020.2994329

Web of Science

J-GLOBAL

Authorship：Lead author   Language：Japanese   Publishing type：Research paper (scientific journal)  

Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：THE JAPAN SOCIETY FOR AERONAUTICAL AND SPACE SCIENCES  

<p>To simulate the motion of a rotor while accelerating during slow descent, a simulation model that corrects errors in data obtained experimentally is developed in this paper. The effect caused by acceleration is expressed as errors in induced velocity and external thrust force, and defined by two correction factors. Best-fit correction factors that provide good approximations for experimental flight data of a bamboo dragonfly are searched and the effectiveness of the method proposed is shown.</p>

DOI： 10.2322/tastj.17.577

CiNii Research

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER INST AERONAUTICS ASTRONAUTICS  

To investigate the effectiveness of a kinetic impactor that accelerates a spacecraft to impact and deflect an Earth-threatening asteroid, a graphical representation, called an impact-geometry map, is proposed in this study. Impact-geometry values that account for changes in asteroid orbital energy at an ideal orbital intersection point for the spacecraft and asteroid were investigated. The impact-geometry map is defined as a contour plot of the impact geometry as a function of the semimajor axis and eccentricity of the spacecraft. The ideal impact of the spacecraft on the asteroid depends on the shape of the injected orbit, and this is well visualized by the impact-geometry map. In addition, the trajectory optimization of photonic solar sails for fictional kinetic-impactor-mission scenarios was performed and the results with an impact-geometry map were investigated. The results were plotted on the impact-geometry map and well reflect the relationship between achievable deflection distance and impact geometry. This paper also highlights the differences between the impact geometry achieved by the mission and the ideal value obtained by the impact-geometry map.

DOI： 10.2514/1.A33985

Web of Science

Language：Japanese  

Language：Japanese   Publishing type：Research paper (other academic)   Publisher：Japanese Society for Engineering Education  

DOI： 10.20549/jseeja.2018.0_26

CiNii Research

Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：THE JAPAN SOCIETY FOR AERONAUTICAL AND SPACE SCIENCES  

<p>Flying cars have been developed as next generation vehicles that enable high speed and flexible door-to-door transportations. A short take-off distance is expected to contribute to increase the possibility that flying cars will be used in our daily life. The purpose of the present study is to investigate to shorten a take-off distance of a flying car by using a wheels' driving force, propeller thrust and lift of main wings. This paper shows that accelerating the car by using wheels is efficient when the velocity is low. On the other hand, using propellers is more efficient when the car approaches to the take-off velocity. As a practical way to shorten the take-off distance, we propose a law to determine the power consumed by propellers and wheels as a function of the velocity of the flying car. Computation results show that the performance of the take-off phase of the flying car can be improved by using a high running ability of the car with wheels. </p>

DOI： 10.2322/jjsass.66.167

CiNii Research

Language：Japanese   Publishing type：Research paper (other academic)   Publisher：The Japan Joint Automatic Control Conference  

DOI： 10.11511/jacc.61.0_1568

CiNii Research

Language：English   Publishing type：Research paper (international conference proceedings)  

Web of Science

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：English   Publishing type：Research paper (international conference proceedings)  

Web of Science

Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：The Japan Society of Mechanical Engineers  

DOI： 10.1299/jsmetokai.2018.67.126

CiNii Research

Language：Japanese   Publishing type：Research paper (other academic)  

Authorship：Lead author   Language：English  

Language：English   Publishing type：Research paper (international conference proceedings)  

Authorship：Lead author   Language：Japanese  

Language：Japanese   Publishing type：Research paper (other academic)  

Language：English  

Language：Japanese   Publishing type：Research paper (conference, symposium, etc.)   Publisher：The Japan Society of Mechanical Engineers  

Collisions between Asteroids and Earth sometimes occur and bring severe damage to human society. Some asteroid deflection techniques to avoid the collisions have been suggested by astronomers and scientists. We discuss these techniques, especially kinetic impactor. In this paper, we think about the improvement of the kinetic impactor by using the concept of Impact Geometry Map which visualizes the maximum change of the asteroid’s orbital energy by an impact. This report suggests a method to increase the change in the orbital energy of the asteroid by using locally optimal thrust vectoring and the Impact Geometry Map. We also use time differentiation of Impact Geometry to make an efficient spacecraft orbit. Additionally, we describe a global trajectory optimization method of spacecraft to increase Impact Geometry.

DOI： 10.1299/jsmesec.2017.26.1a2

CiNii Research

Language：English   Publishing type：Research paper (international conference proceedings)  

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：SPRINGER HEIDELBERG  

An electric solar wind sail uses the natural solar wind stream to produce low but continuous thrust by interacting with a number of long thin charged tethers. It allows a spacecraft to generate a thrust without consuming any reaction mass. The aim of this paper is to investigate the use of a spacecraft with such a propulsion system to deflect an asteroid with a high relative velocity away from an Earth collision trajectory. To this end, we formulate a simulation model for the electric solar wind sail. By summing thrust vectors exerted on each tether, a dynamic model which gives the relation between the thrust and sail attitude is proposed. Orbital maneuvering by fixing the sail's attitude and changing tether voltage is considered. A detailed study of the deflection of fictional asteroids, which are assumed to be identified 15 years before Earth impact, is also presented. Assuming a spacecraft characteristic acceleration of 0.5 mm/s (2), and a projectile mass of 1,000 kg, we show that the trajectory of asteroids with one million tons can be changed enough to avoid a collision with the Earth. Finally, the effectiveness of using this method of propulsion in an asteroid deflection mission is evaluated in comparison with using flat photonic solar sails.

DOI： 10.1007/s40295-015-0081-x

Web of Science

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.2322/tastj.14.Pd_119

Language：English   Publishing type：Research paper (international conference proceedings)  

Several mitigation methods have been studied to various degree of accuracy in the literature to deflect an asteroid from its collision course with the Earth. With the gravity tractor method, the gravitational attraction between the asteroid and a massive spacecraft is used to exert a small force remotely to tow the asteroid in the required direction to avoid an impact. One of the drawbacks of this method is the lack of control over the force produced as it only depends on the mass of the spacecraft and its distance from the asteroid. To overcome this, a new method was introduced: the electrostatic tractor. With this strategy, the deflection force is exerted by means of the electrostatic force produced by artificially charging both a spacecraft and the asteroid, which allows improving the achievable deflection. Our paper discusses a new computation model to investigate the asteroid charging mechanism produced by a plasma contactor placed on the surface of the asteroid. Unlike a simple estimation assuming a cohesive, conductive, and spherical asteroid, our model can handle the case of asteroids with an arbitrary complex shape by solving the Maxwell equations on a 3D mesh. Assuming a quasi-steady condition and an asteroid composed of an Ohmic material, it can be shown that solving the Maxwell equations on the 3D domain is equivalent to solving a Laplace equation for the potential field inside the asteroid. The boundary conditions are introduced by considering the interaction between the charged asteroid and the ambient plasma. This interaction is modeled by equivalent current sources into the surface elements, accounting for the contribution of free electrons, protons, secondary electrons, and photoelectrons, and constitutes a non-linear function of the potential V of the surface elements. Using a finite element approach provides a way to discretize this problem and reformulate it as an equivalent electric network. In this network, adjacent vertices in the mesh are connected via equivalent resistances, which depend on the geometry and the local material properties. Finally, a Newton method is employed to solve the non-linear boundary problem. Analysis for several asteroids are performed with our model and the results of the parametric study about the material, shape, and ambient plasma conditions are provided in the paper.

Scopus

Language：Japanese   Publishing type：Research paper (conference, symposium, etc.)   Publisher：The Japan Society of Mechanical Engineers  

Electric sail uses natural solar wind plasma stream to generate a propulsive force and it allows a spacecraft to perform orbit transfer with small reaction mass. The aim of this paper is to investigate the performance and feasibility of electric sail kinetic impactor for asteroid deflection missions. Asteroid mitigation scenario and simulation model for electric sail are given. Through detailed studies using numerical simulations, performance of electric sail kinetic impactor is emphasized.

DOI： 10.1299/jsmesec.2015.24._B01-1_

CiNii Books

Authorship：Lead author   Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：UNIVELT INC  

The electric sail is a next-generation propulsion system which enables a spacecraft to produce thrust without consuming any reaction mass. It uses a interaction between many charged long thin tethers and the solar wind to produce the propulsive force. This paper discussed the required propertied of the electric sail for kinetic impactor to deflect the near earth asteroids. As fundamental contents, solar wind force model, equations of motion, and orbital maneuvering technique are provided. In addition, more practical theory as the way to calculate the optimal mass model of electric sail and terminal guidance technique are also provided. Those contents are combined into one simulation tool to investigate the efficiency of the electric sail kinetic impactor and required electric sail properties. Through the case study based on real parameters of a near Earth asteroid, required properties of the electric sail and the usability of the developed tool are shown. The relation between the achievable deflection distance and resources of the electric sail are also provided.

Web of Science

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

Authorship：Lead author   Language：Japanese   Publishing type：Research paper (scientific journal)  

DOI： 10.2322/astj.12.79

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.5194/angeo-31-665-2013

Event date： 2023.6

Language：Japanese   Presentation type：Poster presentation  

Venue：Makuhari Messe, Chiba   Country：Japan  

Event date： 2023.6

Language：English   Presentation type：Oral presentation (general)  

Event date： 2023.5

Language：Japanese   Presentation type：Oral presentation (general)  

Country：Japan  

Event date： 2023.2

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：JAXA宇宙科学研究所 研究・管理棟（新A棟）2階会議室A 及び Zoom（ハイブリッド開催）   Country：Japan  

Event date： 2022.9

Language：English   Presentation type：Oral presentation (general)  

Venue：Kumamoto   Country：Japan  

Event date： 2022.2 - 2022.3

Language：English   Presentation type：Oral presentation (general)  

Venue：Online  

Event date： 2022.2

Language：Japanese   Presentation type：Oral presentation (invited, special)  

Venue：オンライン   Country：Japan  

Event date： 2020.10

Language：English   Presentation type：Oral presentation (general)  

Venue：On line  

Event date： 2020.1

Language：English   Presentation type：Oral presentation (general)  

Venue：Orlando, Florida   Country：United States  

Event date： 2018.11

Language：Japanese   Presentation type：Oral presentation (general)  

Country：Japan  

Event date： 2018.10 - 2018.11

Language：English   Presentation type：Oral presentation (general)  

Venue：Jeju Island, Korea   Country：Korea, Republic of  

Event date： 2018.10

Language：Japanese   Presentation type：Oral presentation (invited, special)  

Country：Japan  

Event date： 2018.10

Language：English   Presentation type：Oral presentation (general)  

Venue：San Jose, CA, U.S.   Country：United States  

Event date： 2018.10

Language：English   Presentation type：Oral presentation (general)  

Venue：San Jose, CA, U.S.  

Event date： 2017.12

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：三浦，マホロバマインズ三浦   Country：Japan  

Event date： 2017.11

Language：Japanese   Presentation type：Oral presentation (general)  

Country：Japan  

Event date： 2017.5

Language：English   Presentation type：Poster presentation  

Venue：Tokyo, Japan   Country：Japan  

Event date： 2017.2

Language：Japanese   Presentation type：Oral presentation (invited, special)  

Venue：東京，一橋大学   Country：Japan  

Language：English   Presentation type：Oral presentation (general)  

Venue：San Jose, CA, U.S.  

Language：English   Presentation type：Oral presentation (general)  

Venue：San Jose, CA, U.S.  

Language：Japanese   Presentation type：Oral presentation (general)  

Language：Japanese   Presentation type：Oral presentation (invited, special)  

Language：Japanese   Presentation type：Oral presentation (invited, special)  

Venue：東京，一橋大学  

Language：Japanese   Presentation type：Oral presentation (general)  

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：三浦，マホロバマインズ三浦  

Language：English   Presentation type：Oral presentation (general)  

Venue：Jeju Island, Korea  

Language：English   Presentation type：Poster presentation  

Venue：Tokyo, Japan