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A novel tether-net configuration with double-linked bullets for suppressing reshrinking motion after full deployment

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ACTA ASTRONAUTICA 2025年 226卷 309-324页

作者： Kojima, Hirohisa Trivailo, Pavel M. Tokyo Metropolitan Univ Dept Aeronaut & Astronaut 6-6 Asahigaoka Hino Tokyo 1910065 Japan RMIT Univ Sch Engn Melbourne 3083 Australia

tether-nets have attracted considerable attention as tools for capturing space debris. However, owing to the lack of aerodynamic drag to resist collapse in space, tether-nets tend to shrink back after deployment because of tension in the tether. Various strategies have been proposed to suppress this reshrinking motion before debris capture, such as equipping bullets with thruster modules to control their trajectory after ejection and incorporating a bullet ejection-angle adjustment mechanism. However, these approaches complicate the tether- net design and/or ejection systems. In this study, a novel tether-net configuration comprising double-linked bullets, wherein the inner and outer bullets are connected via a tether, was proposed to prevent the tether-net from reshrinking after full deployment. Upon full deployment, as the bullets start to rebound due to impulsive tension, the outer bullets fly outward, pulling the inner bullets and exchanging momentum to suppress their rebounding motion. The effectiveness of the double-linked bullets in suppressing the reshrinking motion of the tether-net was demonstrated by comparing the results with those obtained using typical single-linked bullets. Furthermore, the influence of the inner and outer bullet mass ratio on the tether-net deployment and reshrinking motion was numerically analyzed to identify the optimal mass ratio for effectively suppressing the reshrinking motion. The results indicate that a mass ratio of 1.0, or slightly less, between the outer and inner bullets is most effective in suppressing tether-net reshrinking.

关键词： tether-net Space debris capture Deployment and rebound Double-linked bullet Bullet ejection angle

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Performance evaluation of tether-net deployment with adjustable ejection angle

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ADVANCES IN SPACE RESEARCH 2024年第5期73卷 2471-2487页

作者： Kato, Yuma Kojima, Hirohisa Trivailo, Pavel M. Tokyo Metropolitan Univ Dept Aeronaut & Astronaut 6-6 Asahigaoka Hino Tokyo 1910065 Japan RMIT Univ Sch Engn Melbourne 3083 Australia

Space debris capture using a tether -net has attracted considerable research attention. To prevent the collapse of the tether -net before debris capture (caused by tension after deployment), various approaches have been proposed, such as the addition of an adhesive material to the tether -net perimeter, use of a net mouth -closing mechanism, or use of a thruster module attached to a weight that controls the weight trajectory after the ejection. However, these mechanisms complicate the net design. To prevent the tether -net collapse prior to debris capture and to ensure its full deployment just before contact with the debris, the tether -net ejection angle must be adjusted in accordance with the distance from the ejector to the debris. In this study, a tether -net ejection mechanism with an adjustable ejection angle is proposed. Moreover, to precisely predict the deployment and bouncing/shrinking behavior of the tether -net, the damping ratio of the net string was determined. Comparison between simulations based on the determined damping ratio and experiments demonstrated good agreement in the maximum deployment area, time to attain the maximum deployment, and the rebound and retraction speeds of the tether -net after complete deployment for large ejection angles. The study findings can contribute to the optimal ejection -angle selection for successful debris capture and prediction of the tether -net behavior after full deployment. (c) 2023 COSPAR. Published by Elsevier B.V. This is an open access article under the CC BY -NC -ND license (http://***/licenses/ by-nc-nd/4.0/).

关键词： Space debris tether-net Ejection mechanism Ejection angle adjustment

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Experiments and dynamic analysis on the closure of tether-net capture for space debris

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Acta Astronautica 2025年 234卷 619-631页

作者： Mengsheng, Li Shuai, Yue Wenhui, Shi Zhen, Zhao Zhonghuaa, Du School of Mechanical Engineering Nanjing University of Science and Technology Nanjing210000 China Shanghai Academy of Spaceflight Technology Shanghai201109 China

Space tether-net capture represents a promising solution for active space debris removal. This study proposes a gunpowder-actuated separable closing mechanism to ensure effective debris containment within the tether-net during the post-capture phase. A ground-based experiment was developed to validate the feasibility of this method, with parallel development of a high-fidelity finite element model (FEM) employing nonlinear dynamic analysis to simulate the tether-net behavior. A comparison between experimental and simulation results revealed a deviation of less than 15 % in closure lengths, with strong morphological agreement in net configuration. To explore the effects of key parameters on closure performance, a capture model for spherical targets was established. Multi-parameter analysis revealed that higher separation forces reduced closure time, though excessively high forces increased the risk of line failure. A lower mass ratio of separation bodies accelerated closure and improved performance. Additionally, delaying the closure actuation time reduced the device's closure time. Therefore, it is recommended to delay the closure actuation time slightly to optimize performance by combining inertial closure with the closure device mechanism. Through systematic analysis of the closing mechanism's performance, it becomes feasible to refine its operational parameters, ultimately achieving an optimal closure for the designated target. © 2025

关键词： Closure performance Dynamic analysis Separable closing mechanism Space debris tether-net

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Study and evaluation of tether-net parameters for space debris capture using modified capture quality index

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JOURNAL OF SPACE SAFETY ENGINEERING 2024年第4期11卷 750-766页

作者： Pandie, Andry Renaldy Tokyo Metropolitan Univ Dept Aeronaut & Astronaut 6-6 Asahigaoka Hino Tokyo 1910065 Japan

The increasing volume of space debris presents a significant threat to spacecraft safety and the long-term viability of space missions. Among the proposed methods for capturing and removing small space debris at low relative velocities, the tether-net method emerges as particularly promising. Identifying and evaluating the parameters influencing the capture process through simulations is imperative to ensure the effective capture of debris by the net and to assess its efficiency. Therefore this study investigates the influence and effectiveness of various parameter combinations through simulations. The study examines the effects of parameters such as net and space debris masses, shooting speed of the corner mass (CM), CM ejection angle, and activation or deactivation of the net mouth closure mechanism on the space debris-capturing capacity. The capture effectiveness evaluation was conducted utilizing the modified capture quality index ( MCQI). During simulations where the closure mechanism was not activated, the net opened upon debris contact, resulting in expulsion and decreased MCQI. Conversely, activation of the closure mechanism enhanced the probability of capturing space debris. Within the "wrap" category, parameter combinations of medium CM ejection angles, extended initial distances, and high shooting speeds yielded the highest capture quality for debris capture, as confirmed by the MCQI. Conversely, a larger CM ejection angle and other parameters reduced the likelihood of debris capture, indicating an inverse relationship between the ejection angle and the initial distance between the net and the debris. (c) 2024 International Association for the Advancement of Space Safety. Published by Elsevier Ltd. All rights are reserved, including those for text and data mining, AI training, and similar technologies.

关键词： Capture quality Closure mechanism Combinations Space debris removal tether-net

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Learning Robust Policies for Generalized Debris Capture with an Automated tether-net System

Learning Robust Policies for Generalized Debris Capture with...

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AIAA Science and Technology Forum and Exposition (AIAA SciTech Forum)

作者： Zeng, Chen Hecht, Grant KrisshnaKumar, Prajit Shah, Raj Kalpeshkumar Chowdhury, Souma Botta, Eleonora M. Univ Buffalo Dept Mech & Aerosp Engn Buffalo NY 14260 USA

ISBN: (纸本)9781624106316

tether-net launched from a chaser spacecraft provides a promising method to capture and dispose off large space debris in orbit. This tether-net system is subject to several sources of uncertainty in sensing and actuation that affect the performance of its net launch and closing control. Earlier reliability based optimization approaches to design control actions however remain challenging and computationally prohibitive to generalize over varying launch scenarios and target (debris) state relative to chaser. To search for a general and reliable control policy, this paper presents a reinforcement learning framework that integrates a proximal policy optimization (PPO2) approach with net dynamics simulations. The latter allows evaluating the episodes of net-based target capture, and estimate the capture quality index that serves as the reward feedback to PPO2. Here, the learnt policy is designed to model the timing of the net closing action based on the state of the moving net and the target, under any given launch scenario. A stochastic state transition model is considered in order to incorporate synthetic uncertainties in state estimation and launch actuation. Along with notable reward improvement during training, the trained policy demonstrates capture performance (over a wide range of launch/target scenarios) that is close to that obtained with reliability based optimization run over an individual scenario.

关键词： Active Debris Removal Reinforcement Learning tether-net Uncertainty

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Dynamics modeling and simulation of self-collision of tether-net for space debris removal

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ADVANCES IN SPACE RESEARCH 2019年第9期64卷 1675-1687页

作者： Si, Jiyue Pang, Zhaojun Du, Zhonghua Cheng, Chun Nanjing Univ Sci & Technol Sch Mech Engn Nanjing 210094 Jiangsu Peoples R China

tether-net is a new active removal technology for space debris, and its deployment and capture have attracted considerable attention. This study focuses on the dynamics and simulation of self-collision of tether-net. First, the mass-spring-damper method is used to model tether-net and a line-line self-collision detection algorithm is proposed according to the geometric characteristics of tether-net. Thereafter, combined with the nonlinear collision model, the self-collision process of tether-net is studied. Two simulations of the close-up of a net with or without a target are executed to show the difference between considering and not considering the self-collision of tether-net. Results reveal that the capture process of tether-net with consideration for self-collision is different from the one without self-collision, especially after the corners of the net begin to contact each other. (C) 2019 COSPAR. Published by Elsevier Ltd. All rights reserved.

关键词： Space debris tether-net Contact modeling Self-collision

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Experiments and simulation of a net closing mechanism for tether-net capture of space debris

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ACTA ASTRONAUTICA 2017年第Oct.期139卷 332-343页

作者： Sharf, Inna Thomsen, Benjamin Botta, Eleonora M. Misra, Arun K. McGill Univ Dept Mech Engn Room 270817 Sherbrooke St West Montreal PQ H3A 0C3 Canada

This research addresses the design and testing of a debris containment system for use in a tether-net approach to space debris removal. The tether-net active debris removal involves the ejection of a net from a spacecraft by applying impulses to masses on the net, subsequent expansion of the net, the'envelopment and capture of the debris target, and the de-orbiting of the debris via a tether to the chaser spacecraft. To ensure a debris removal mission's success, it is important that the debris be successfully captured and then, secured within the net. To this end, we present a concept for a net closing mechanism, which we believe will permit consistently successful debris capture via a simple and unobtrusive design. This net closing system functions by extending the main tether connecting the chaser spacecraft and the net vertex to the perimeter and around the perimeter of the net, allowing the tether to actuate closure of the net in a manner similar to a cinch cord. A particular embodiment of the design in a laboratory test-bed is described: the test-bed itself is comprised of a scaled-down tether-net, a supporting frame and a mock-up debris. Experiments conducted with the facility demonstrate the practicality of the net closing system. A model of the net closure concept has been integrated into the previously developed dynamics simulator of the chaser/tether-net/debris system. Simulations under tether tensioning conditions demonstrate the effectiveness of the closure concept for debris containment, in the gravity-free environment of space, for a realistic debris target. The on-ground experimental test-bed is also used to showcase its utility for validating the dynamics simulation of the net deployment, and a full-scale automated setup would make possible a range of validation studies of other aspects of a tether-net debris capture mission.

关键词： Space debris Debris removal tether-net Closing mechanism On-ground test-bed Experiments Deployment dynamics

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Simulation and tension control of a tether-actuated closing mechanism for net-based capture of space debris

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ACTA ASTRONAUTICA 2020年 174卷 347-358页

作者： Botta, Eleonora M. Miles, Corey Sharf, Inna Univ Buffalo Dept Mech & Aerosp Engn 240 Bell Hall Buffalo NY 14260 USA McGill Univ Dept Mech Engn Room 270817 Sherbrooke St West Sherbrooke PQ H3A 0C3 Canada

The growth of space debris in Earth's orbit is recognized as a serious threat to future space missions. To contain the growth of space debris in the long term, active removal of large defunct spacecraft is needed. A promising solution to this problem is the use of tether-nets. In the envisaged mission, a net is released from a chaser spacecraft toward a target debris;the net entangles the debris and the tether provides a flexible link between chaser and debris to tug the debris to a disposal orbit. The present work is focused on the simulation and control of a tether-actuated closing mechanism. In this concept, proposed only recently, the tether is looped through the center of the net and around the perimeter, and spooling the tether in draws the net perimeter closed. In this paper, a dynamic model of a tether-actuated closing mechanism for net-based capture of space debris is developed. The model of the winch, which is key to the control of the closing mechanism, is established based on literature on the design of reeling mechanisms for tether-nets. Two control laws for the winch velocity during deployment and closure of the net, respectively, are formulated and tested in simulation. Simulations of the capture of a Zenit-2 rocket upper stage are performed using a proportional-derivative tension control law with gain scheduling based on tether length. Results support feasibility of the tether-actuated closing mechanism.

关键词： Space debris Active debris removal tether-net Closing mechanism Tension control Gain scheduling

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Simulation of tether-nets for capture of space debris and small asteroids

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ACTA ASTRONAUTICA 2019年第Feb.期155卷 448-461页

作者： Botta, Eleonora M. Sharf, Inna Misra, Arun K. McGill Univ Dept Mech Engn Room 270817 Sherbrooke St West Montreal PQ H3A 0C3 Canada

One of the most promising techniques to capture large debris on orbit consists in the use of tether-nets. With this concept currently at a medium technological readiness level only, numerical studies on tether-net removal missions are still needed. This paper presents a versatile simulator developed with the aim of gaining insight into the dynamics of tether-net capture of space debris. Its modular architecture supports multiple modeling choices and allows simulating diverse capture scenarios with different system designs. Simulation results are shown for the capture of a realistic launcher upper stage with the representation of the main components of the system, consisting in chaser, main tether, net, and two possible configurations of a closing mechanism. It is shown that only a closing mechanism with more than one attachment to each side of the net can guarantee containment of this type of debris after capture. It is also observed that a safer capture scenario is one in which the axis of rotation of the target is parallel to the direction of ejection of the net. Additional simulation results suggest that tether-nets could be used to capture not only large debris, but also small asteroids, and that this simulator could enable future studies.

关键词： tether-net Active debris removal Debris capture Asteroid capture

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A quality index for net-based capture of space debris

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ACTA ASTRONAUTICA 2020年 176卷 455-463页

作者： Barnes, Charles M. Botta, Eleonora M. Univ Buffalo Dept Mech & Aerosp Engn 240 Bell Hall Buffalo NY 14260 USA

Before net-based debris removal missions are put in place, large simulation studies are needed to analyze the reliability of capture and define preferred designs and capture conditions. Therefore, evaluation of capture success in a simulation environment has to be automated. In this paper, a capture quality index apt to the quantitative evaluation of the success of capture is proposed. The quality index is based on volume, surface area, and distance metrics. Various parameters composing this index are analyzed in this paper, with the aim to recognize successful and unsuccessful captures reliably, starting from the moment the net is ejected to the final capture. Alpha shape was explored as an alternative to convex hull for approximating the shape of the net, but was deemed inconsistent. For the distance metrics, the reference distance was chosen as the smallest distance from the center of mass of the target to its surface. Variations in the modeling of the target were investigated. Results indicate important improvements in the performance of the capture quality index compared to previous research. The resulting quality index proves to be a useful tool to differentiate between a successful and an unsuccessful capture.

关键词： Space debris Capture Quality index tether-net Simulation net-based capture success

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