Nobukatsu Okuizumi

Mission Report on The Solar Power Sail Deployment Demonstration of IKAROS

Hirokata Sawada Japan Aerospace Exploration Agency, Kanagawa, 252-5210, JAPAN Osamu Mori 2 Japan Aerospace Exploration Agency, Kanagawa, 252-5210, JAPAN Nobukatsu Okuizumi Japan Aerospace Exploration Agency, Kanagawa, 252-5210, JAPAN Yoji Shirasawa University of Tokyo, Tokyo, JAPAN Yasuyuki Miyazaki Nihon University, Chiba, 274-8501, JAPAN Michihiro Natori Waseda University, Tokyo, 169-8555, JAPAN Saburo Matunaga Tokyo Institute of Technology, Tokyo, 152-8552, JAPAN Hiroshi Furuya Tokyo Institute of Technology, Tokyo, 152-8552, JAPAN Hiraku Sakamoto Tokyo Institute of Technology, Tokyo, 152-8552, JAPAN

Multiple time scale analysis of hysteretic systems subjected to harmonic excitation

Abstract Dynamic behavior of smooth hysteretic systems subjected to harmonic excitation is analyzed. Wens differential equation model for hysteresis, which can be applied to a large class of hysteretic systems, is used. A piecewise power series expression for hysteretic restoring force is derived from Wens model assuming that steady state force–displacement curve draws a single loop and that the non-linearity of the restoring force is weak. The method of multiple scales is applied to the equation of motion by using the piecewise power series expression for the cases of primary and secondary resonance to derive the approximate solutions and the differential equations governing the amplitude and phase of the solutions. Phase plane trajectories, resonance curves and stability limit of the solutions are obtained and compared with the results of numerical integration in order to examine the validity of the present analysis.

Fundamental Strategies for Control of a Tethered System in Elliptical Orbits

Fundamental strategies for libration control and deployment of a tethered system in elliptical orbits are presented. Through the physical interpretations of the dynamic behavior of tethered systems in elliptical orbits, it is shown that the periodic solution is proper as a control objective. An on ‐off control strategy using a thruster installed to the subsatellite is examined in elliptical orbits, and the periodic on ‐off control, which acts at certain true anomalies in the orbit, is presented as the fundamental strategy. For tether deployment, uniform rate deployment is examined in elliptical orbits through physical interpretations of the equations of motion and numerical simulations, and it is shown that the slower deployment is preferable to deploy a tether closer to the periodic solution at the end of the deployment. It is considered that the strategies presented in this study can be applied to tethered systems in orbits of an arbitrary eccentricity, as far as the libration is possible.

Dynamic Behavior of a Tethered System with Multiple Subsatellites in Elliptic Orbits

Dynamic behavior of a tethered system with multiple subsatellites subjected to both atmospheric drag and changes of gravity gradient in elliptic orbits is investigated. The tethered system is modeled as a combination of rigid-body subsatellites and lumped tether masses, and flexibility of the tether is considered. The results of the numerical experiments show that the libration of the total system can diverge due to the atmospheric drag, and the total system begins tumbling motion later. The physical interpretation is clearly presented by focusing on the deviation from the periodic motion. Effects of the atmospheric drag on the attitude motions of the subsatellites and the tension states of the tether are also investigated. It is shown that the large perturbations can cause partial slack states of the tether, which causes unstable attitude motions of some of the subsatellites.

Periodic Solutions and Controls of Tethered Systems in Elliptic Orbits

In this paper we study the periodic solution of the librational motion of a tethered system in elliptic orbit and clarify its mechanical characteristics. Basic libration control toward the periodic solution is also presented. A tethered system is modeled as a rigid body, and a set of nonlinear equations of motion about the librational and the orbital motions is formulated. An approximated analytical solution is obtained through the Lindstedt perturbation method. The total mechanical energy is formulated, and it is shown that it has the minimum value when the librational and orbital motions coincide with the periodic solution. This means that the periodic solution is the minimum energy solution, and that the periodic solution in an elliptic orbit has the same significance as the equilibrium state in a circular orbit from the mechanical point of view. A libration control toward the periodic solution is also investigated, and the effectiveness of this control strategy is demonstrated by using the periodic on-off control through a thruster installed on the subsatellite.

Deformation Properties of Solar Sail IKAROS Membrane with Nonlinear Finite Element Analyses

This paper discusses the deformation properties of the solar sail IKAROS membrane to identify the possible causes of the phenomena observed by the flight data: mechanics of higher out-of-plane stiffness of the IKAROS membrane. Two possible causes are hypothesized in this paper; the bending stiffness increased by the curvature of thin-film solar cells, and the deformation mode changed by the curvature. Although the second moment of area of the sail membrane is calculated by the natural vibration analyses, the effects of the bending stiffness increased by the curvature on the out-of-plane displacement is small. The effects of the deformation mode on the out-of-plane displacement is examined by geometrically calculating the relationships between the sensitivity of the margin in a circumferential length to the displacement. The results indicate that the sensitivity becomes small as the curvature becomes large. Thus, the high out-of-plane stiffness of the IKAROS membrane can be induced by the increased bending stiffness and by the changed deformation mode due to the curvature of the solar cells.

Evaluation of Sail Mechanics of IKAROS on its Slow-Spin and Reverse-Spin Operation

In the post operational phase of spin type solar sail “IKAROS”, a slow-spin operation and a reverse-spin operation were conducted to acquire basic knowledge of mechanics of sail membrane. The flight data indicates that the sail membrane kept its shape against the solar radiation pressure even with low centrifugal force.

Nonflatness of Solar Sail Membrane Predicted by Nonlinear Finite Element Analyses

This paper identifies the possible causes of two phenomena observed in the membrane of the solar sail IKAROS: its nonflat shape and high out-of-plane stiffness. IKAROS’ flight data showed that the sail was significantly nonflat. In addition, the out-of-plane deformation of the membrane was smaller than that predicted preflight by numerical simulations, which indicates higher out-of-plane stiffness than expected. This study hypothesized that the initial deformation of the membrane could have been induced by the curvatures of the thin film solar cells and the reflection control devices attached on the sail. The effects of the curvatures on the sail shape were examined through geometrically nonlinear finite element analyses of a 1/4 IKAROS membrane with shell elements. The analysis results indicated that the on-orbit IKAROS membrane could be nonflat owing to the propagation of wrinkles throughout the membrane induced by the curvature of the thinfilm components. Furthermore, the out-of-plane deformation of the sail under solar pressure became very small when the entire sail was wrinkled, which explains IKAROS’ on-orbit phenomena.

Stepwise deployment of membrane structures with rolled-up booms: Experiments and simulations

In this paper, simple deployable structures are introduced, which consist of polygonal membranes and elastic booms deployed by only releasing the rolled-up booms in stepwise manners. The membranes are folded up with modified spiral folding patterns to fit the arrangement of booms. The booms are newly-developed bi-convex tapes covered by braids. Basic mechanical test results of the booms are first presented. Deployment experiments of a small conceptual model are demonstrated for several configurations. Numerical simulations of the deployment experiments are also performed employing multi-particle approximation method for membranes and a discrete model for one-dimensional continuum for the booms. The results are compared with the experimental results and the deployment behaviors of the structures are discussed.

Deployable membrane structures with rolled-up booms and their deployment characteristics

1 Visiting Professor, Advanced Research Institute for Science and Engineering, 3-4-1 Okubo / 55S-608, Associate Fellow AIAA 2 Research Associate, Department of Modern Mechanical Engineering, 3-4-1 Okubo / 59-314 ; presently, Assistant Professor, Department of Mechanical, Aerospace and Materials Engineering, Muroran Institute of Technology, 27-1 Mizumoto, Muroran, Hokkaido 050-8585, Japan, Member AIAA 3 Assistant Professor, Department of Space Flight Systems, 3-1-1 Chuoh-ku Yoshinodai, Member AIAA 4 Chief Engineer, 14-10 Shimoyasuta, Maruoka-cho, Member AIAA 5 Professor and Dean, 3-4-1 Okubo, Member AIAA Deployable Membrane Structures with Rolled-up Booms and Their Deployment Characteristics