森 治

This paper proposes a method to store a large solar-sail membrane while ensuring repeatability of its stored configuration. The feasibility and effectiveness of the method is verified through a series of sail-storage experiments using 10m-size membranes. Large membranes used as a solar sail should be stored compactly to save the launch volume; in addition, their stored configuration should be sufficiently predictable in order to guarantee reliable deployment in orbit. However, it is difficult to store a large membrane compactly with sufficient repeatability because of the finite thickness of the membrane. This paper classifies the existing and proposed folding patterns that can consider the finite-thickness of membranes. This paper then demonstrates the feasibility of "bulging roll-up" experimentally, and evaluates the repeatability of its stored configuration quantatively. © 2013 by the American Institute of Aeronautics and Astronautics, Inc. All rights reserved.

The world's first solar sail IKAROS (Interplanetary Kite-craft Accelerated by Radiation Of the Sun) which is operated by Japan Aerospace Exploration Agency (JAXA) lost communication with the ground station due to the power shortage on December 24, 2011. In order to acquire IKAROS again after the power comes back, we immediately initiated to predict the attitude and orbit for the spacecraft. As the result of the effort for the prediction, finally we acquire IKAROS after 9 months. This paper presents that the attitude and orbit prediction technique, while IKAROS was lost in space. © 2013 2013 California Institute of Technology.

This paper presents IKAROS extended missions. IKAROS entered its extended operation phase at the beginning of 2011. In the extended operation, the spin rate was decreased to observe the deformation of the sail under low centrifugal force environment. On Oct. 18, 2011, IKAROS transferred to the reverse spin to enhance the knowledge about the effect of stiffness of membrane against the solar radiation pressure. We investigated the change of the attitude motion by the reverse spin mission. At the end of 2011, IKAROS moved to hibernation mode because the Sun angle was increased. We searched for IKAROS considering the attitude and orbital motion during hibernation. On Sep. 6, 2012, we succeedcd in tracking IKAROS which came out of hibernation. A solar power sail can be a hybrid propulsion system with a solar sail by activating the ultra-high specific impulse ion engines with the power generated by thin film solar cells. This paper also introduces an advanced solar power sail mission toward Jupiter and Trojan asteroids via hybrid electric photon propulsion.©2012 by the International Astronautical Federation.

The power supply management system was originally developed at JAXA to manage the risk of electric power scarce due to excess access from each device. The main idea is to decrease the peak amount of limited power in a spacecraft by changing in switching time based on demand-response from each device. For realization, the system features "decentralized system" and "priority setting" on each device. The decentralized system, in which each device has its own controller and changes information each other, contributes to the robustness of the system since a defect of the controller does not affect other parts of the system while the limited power is allocated based on the priority level of each device. Experiments were taken for heater control equipment to demonstrate the practical performance of the novel power system. In the experiments, six devices were prepared with heater controllers which received duty signals, and set the target temperature for each of the devices. The experiments were initiated by providing sufficient power and checked if all the devices were fully working, and then decreased the power supply to observe the behavior of the temperatures under limited resource. As a result, all of the devices met the temperature requirements even under short energy supply. To quantitatively evaluate the benefits of the new system when applied to public infrastructure systems, multiple small electrical trains (HO gauge) whose electrical power provision system is basically the same as the real one have been arranged. The experiments also give the deeper understanding of behavior of first-order motor-driven system in view point of energy consumption. Presently, the priority setting system is being implemented to the small train system, to show whether similar results as the heater control case are also achieved. In conclusion, this paper will present the newly constructed power system and elaborate its ramifications together with the experimental and simulation results. Copyright © (2012) by the International Astronautical Federation.

Solar power sail is a deep space probe to be powered by hybrid propulsion of solar photon acceleration and ion engines to explore outer planetary region of the Solar System without relying on nuclear technology. The Japan Aerospace Exploration Agency (JAXA) launched the world's first deep space solar sail demonstration spacecraft "IKAROS" (Interplanetary Kite-craft Accelerated by Radiation Of the Sun) on May 21, 2010. IKAROS succeeded in deploying a 20m-span solar sail on June 9 and demonstrated several key technologies for solar sail utilizing the deep space flight environment. JAXA is currently studying an outer solar system exploration mission using the demonstrated solar power sail technology. The mission plans to fly for Jupiter, where the spacecraft drops a tiny Jovian probe and performs a swing-by for a Trojan asteroid. Current scenario consists of the rendezvous with one of the Trojan asteroids that are at the Lagrange points L4/L5 associated with Sun-Jupiter system. About as large as 50m sail should be deployed for this mission according to preliminary mission analysis and related research is intensively being carried out in JAXA. JAXA plans to initiate the project in a few years and looks at the launch around 2020. © 2012 by JAXA.

This paper describes an analysis for the membrane dynamics and deformation of solar power sail demonstrator "IKAROS". After the successful deployment of membrane, some images of the whole sail membrane of IKAROS were taken by separation cameras. From these data, it has estimated that the membrane of IKAROS had a deformation different from the prediction considering the solar radiation pressure. In this paper, these observed deformations of membrane are reported and compared with the results of numerical simulation using multi-particle model. A membrane's deformation over time observed in the images taken by side monitor cameras is also reported and the cause of the changing is discussed. © 2012 by the American Institute of Aeronautics and Astronautics, Inc. All rights reserved.

Japan Aerospace Exploration Agency (JAXA) launched the solar power sail orbiter "Interplanetary Kite-craft Accelerated by Radiation Of the Sun: IKAROS", on May 21st, 2010. IKAROS was launched by H-IIA 17th vehicle with "Venus Climate Orbiter: AKATSUKI". IKAROS demonstrates a new propulsion technology of utilizing photons from the sun for deep space exploration, which is called the Solar Power Sail technology. In a case of the solar system exploration, an ion-propulsion engine is effective as a main propulsion system because it has high specific impulse and it can provide a continuous acceleration. However, the ion-engine needs high electric power in proportion to its performance. The solar power sail technology can be a hybrid engine, which can provide high electric power generated by very thin flexible solar arrays attached on the solar sail, while obtaining acceleration generated on the solar sail by the sun radiation. IKAROS succeeded in deployment the solar power sail in an interplanetary orbit, on June 9th, 2010, the first in the world, and we could obtain various flight data of the solar power sail deployment mission, and. In this paper, we will introduce a detail of our estimation method by using monitor camera images and separation camera images. Furthermore, we will report the shape estimation results using calibrated images and luminance information of every pixel. © 2012 by the American Institute of Aeronautics and Astronautics, Inc. All rights reserved.

In this paper, the attitude dynamics of IKAROS, which is spinning solar sail, is presented. Multi Particle Model (MPM) and First Mode Model of out-of-plane deformation (FMM) are introduced to analyze the out-of-plane oscillation mode of spinning solar sail. Considering the thruster configuration of IKAROS, the force on main body and membrane by thruster plume as well as reaction force by thruster are integrated into MPM. The attitude motion after sail deployment or reorientation using thrusters can be analyzed by MPM numerical simulations precisely. The out-of-plane oscillation of IKAROS is governed by three modes derived from FMM. FMM is simple and valid for the design of attitude controller. Copyright ©2010 by the International Astronautical Federation. All rights reserved.

In this paper, the attitude dynamics of IKAROS, which is spinning solar sail, is presented. Multi Particle Model (MPM) and First Mode Model of out-of-plane deformation (FMM) are introduced to analyze the out-of-plane oscillation mode of spinning solar sail. Considering the thruster configuration of IKAROS, the force on main body and membrane by thruster plume as well as reaction force by thruster are integrated into MPM. The attitude motion after sail deployment or reorientation using thrusters can be analyzed by MPM numerical simulations precisely. The out-of-plane oscillation of IKAROS is governed by three modes derived from FMM. FMM is simple and valid for the design of attitude controller. Copyright ©2010 by the International Astronautical Federation. All rights reserved.

A plume impingement analysis on the thruster deck and the membrane of IKAROS was performed based on available flight data. IKAROS employs gas-liquid thruster system as RCS for spin-rate adjustment and attitude control. Gas jet plume from the thruster nozzles leads to considerable undesired disturbance force on the spacecraft, because IKAROS has a large size of flexible membrane whose diagonal distance is 20m. To minimize thrust loss by means of improvement in maneuver planning and to obtain the local distribution of the momentum flux on the membrane for future solar sail missions design, it is important to evaluate the plume impingement on the solar and propose a plume distribution model. Therefore this paper presents actual values of mechanical load on IKAROS and provides a distribution of plume force on the surface. In proposal of a plume model, the conventional plume density distribution model [1] and plume impingement model [2] were used. And parameters in these models that describe the physical interaction between plume flow and the surface of membrane were identified based on fight data.

Japan Exploration Agency (JAXA) launched a powered solar sail "Interplanetary Kite-craft Accelerated by. Radiation Of the Sun (IKAROS)" on May 21, 2010. One of the primal technologies demonstrated at IKAROS is the deployment of the sail whose diameter is 20m class. After the launch, the deployment operation was performed and successful expansion of the sail was confirmed. The deployment sequence in IKAROS consists of static first stage and dynamic second stage. In this paper, the flight data and observed dynamic motion during the first stage deployment are reported. These are compared with the results of numerical simulations using multi-particle model, and the accuracy and availability of this model is discussed. Copyright ©2011 by the International Astronautical Federation. All rights reserved.

It is well known that the thrust force of the solar sail due to the solar radiation pressure is changed by the orientation of the sail with respect to the Sun direction. Therefore, the orbit of the solar sail can be controlled by changing the attitude of the spacecraft. In this study, we consider the spinning solar power sail IKAROS (Interplanetary Kite-craft Accelerated by Radiation Of the Sun), which succeeded to become the world's first flight solar sail in orbit. The IKAROS attitude, i.e. the spin-axis direction is nominally controlled by the rhumb-line control method. By utilizing the solar radiation pressure (SRP) torque, however, we are able to change the direction of the spin-axis only by controlling its spin rate. This is because the spin axis direction relates to the balance between the angular momentum of spinning and the SRP torque. Thus, we can control the solar sail's orbit by controlling the spin rate. The main objective in this study is to construct the orbit control strategy of the spinning solar sail via the spin rate control.