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The electrodynamic tether (EDT) is a type of propulsion system that uses the geomagnetic field and ionospheric plasma and has the potential to conduct a space-debris removal mission without consuming a large amount of propellant. To understand the dynamic properties of the bare EDT system, an orbital dynamic model based on a detailed environmental space model and the real discharge characteristics of a hollow cathode plasma contactor (HCPC) was built. By numerical simulation, the differences in the bare tether performance caused by various orbital conditions and HCPC voltage models (at constant or various voltages) were compared and discussed. The results suggest that dynamic distinctions generated by the two bias voltage models increased as the latitude increased from 0° to 60°.

This paper studied the dynamic characteristics of electrodynamic tethered satellite with consideration of coupled multiphysics field for orbital boost maneuver by a fully insulated electrodynamic tether (EDT). We proposed a simplified analytical nonlinear current–voltage circuit method based on the Parker–Murphy model to evaluate the real-time electric current-carrying tether. Furthermore, the performances of orbital boost maneuver by a fully insulated electrodynamic tether is investigated. This current–voltage model is influenced by the electron density, the intensity of Earth’s magnetic field and the space plasma temperature. The hollow plasma contactor located on the sub-satellite to attract the electrons from the ambient plasma. An on-board power supply is adopted to change the direction of electric current for boosting the system. The direction of electric current in tether is from main-satellite to sub-satellite. The efficiency of orbital boost maneuver is compared with different sizes of anodic contactors and the given voltage of power supply. The simulation results showed that electric current is easily affected by the fluctuation of electron density, the Earth’s magnetic field and plasma temperature. The electrodynamic tether system can stable boost its orbit altitude from 400 to 1200 km in four cases by a fully insulated electrodynamic tether.

Various promising applications of electrodynamic tether have been proposed for space missions over the past decades. A crucial issue of these missions is to deploy an electrodynamic tether under a rapid and stable state. This paper aims to stabilize the libration motions of a bare electrodynamic tether during its three-dimensional deployment. The tethered system under consideration consists of a main-satellite and a sub-satellite connected to each other through a bare electrodynamic tether. A widely used dumbbell assumption considering the tether as rigid and inflexible is adopted to facilitate the dynamic modeling and analysis of the tethered system. A pair of active control laws is synthesized by simultaneously regulating the electric current and tether tension to achieve an efficient stabilization of the three-dimensional libration of the bare electrodynamic tether in the deployment process. Moreover, comparisons of three groups of numerical simulations are performed to evaluate the in uences of orbital inclinations and geomagnetic field models and the performance of the active control laws.

This paper is concerned with an approach for active removing of space debris by electrodynamic tether (EDT) systems in a time-optimal maneuver. In this regard, a collector–emitter system is comprised of the insulated EDT in order to generate the required electric current over a virtual circuit once the induced electric current is adopted as control force producer. To this end, a simulation program is initially developed, during which dynamic and mathematical models of the EDT as well as the geomagnetic field are encompassed, respectively. This toolset is first utilized for prediction of orbital characteristics during the deorbit process; and subsequently, using the direct transcription method, the time-optimal problem is well solved. The efficacy of the suggested technique is verified through extensive simulations once all hard constraints of the underlying problem are well satisfied. In short, while the altitude varies from 1413 to 200 km, the optimized deorbit time would reduce about 17 days.

This study develops a coupled multiphysics finite element method forthe dynamic analysis of a bare flexible electrodynamic tether. Contrary tothe existing methods, the new method discretizes and solves the orbitalmotion limited equation and the dynamic equation of an elastic flexibletether simultaneously. First, the new method is verified via comparison withthe existing methods in a straight tether situation. Second, the number oftether elements, tether bending deformation, and two design parameters atthe cathodic end affecting the electrical current are investigated. It isdetermined that the tether bending deformation and the two parameters i.e.,the impedance $Z_{T}$ and $\varPhi_{\rm~PW}$ have asignificant impact on the electron collection efficiency of anelectrodynamic tether system. The results indicate that the proposed methodshould be applied in the refined mission analysis.

Dynamics is one of the fundamentally important aspects of all space tether research. This paper derives the dynamic equations of electrodynamic tether system (EDT) in stationkeeping phase using Newton’s laws. This paper further analyzes the tether system motion rules under electrodynamic drag, gravity induced force, and tether tension. Numerical simulation of electrodynamic tether system in station-keeping phase is calculated using an approach that combines the central difference method, fourth-order Runge-Kutta method, and predictor-corrector method, among others. The simulation results show that the motion of electrodynamic tether in stationkeeping phase not only contains librations caused by the motion of endmass, but also contains vertical and longitudinal vibrations of tether. If the motion of endmass is ignored, it is much similar to the vibration of cable with two immovable pinned-supports, in which the mid-span has the largest amplitude of vibration. Based on this, the main satellite and the endmass at both ends of tether can be treated as immovable pinned-supports when the tether vibration and tension of electrodynamic tether system in impermanency are investigated.

The equilibrium states of an electrodynamic tether between two bodies of small mass in a near-polar orbit are studied. The behavior of the following parameters is traced during an astronomical day: tension of the tether, its radius of curvature, the angle of deviation from the orbital plane, induced electrodynamic force, etc. The lifetime of the tether in a circular near-earth orbit is analyzed

A detailed, geometrically exact bifurcation analysis is performed for a model of a power-generating tethered device of interest to the space industries. The structure, a short electrodynamic tether, comprises a thin, long rod that is spun in a horizontal configuration from a satellite in low Earth orbit, with a massive electrically conducting disk at its free end. The system is modelled using a Cosserat formulation leading to a system of Kirchhoff equations for the rod's shape as a function of position and time. Moving to a rotating frame, incorporating the effects of internal damping, intrinsic curvature due to the deployment method and novel force and moment boundary conditions at the contactor, the problem for steady rotating solutions is formulated as a two-point boundary value problem. Using numerical continuation methods, a bifurcation analysis is carried out varying rotation speeds up to many times the critical resonance frequency. Spatial finite differences are used to formulate the stability problem for each steady state and the corresponding eigenvalues are computed. The results show excellent agreement with earlier multibody dynamics simulations of the same problem.

The SET (short electrodynamic tether) is an extremely flexible deployable structure. Unlike most other tethers that orbit with their axis of smallest moment of inertia pointing towards the Earth's center (natural position), the SET must orbit with its axis of smallest inertia normal to the orbit plane. The Faraday effect allows the SET to modify its orbit in this position. This is due to the interaction of the Earth's magnetic field with the tether, which is an electric conductor. In order to maintain the aforementioned operating position, the SET is subjected to a spin velocity around its axis of smallest inertia. If the system were rigid, the generated gyroscopic pairs would guarantee the system's stability. The tether is not perfectly straight after deployment. This fact could make the rotation of the structure unstable. The problem is similar to the instability of unbalanced rotors. The linear study of unbalanced systems predicts the structural instability once a certain critical velocity is exceeded. Instability is due to internal damping forces. The spin velocity of the SET is greater than the critical velocity. Nevertheless, certain works that include the geometric nonlinearities show a stable behavior under such conditions. The object of this paper is to try to verify these results for the SET. The SET consists of a 100-meter tether with a concentrated mass at its end. The system has been modeled using the floating reference frame approach with natural coordinates. The substructuring technique is used to include nonlinearities in the system.

Two important applications of electrodynamics tethers, among others, are those of using them for deorbiting and/or propulsion. A crucial issue for both of the above applications is the dynamic stability of the tether system. The electrodynamic forces on the tether couple, in fact, in-plane and out-of-plane oscillations and, especially for light systems, can drive the tethers unstable. In both the applications of deorbiting and propulsion, the tether system is supposed to operate for long intervals of time (months) so that a crucial issue, in view of the fact that the system is potentially unstable, is that of analyzing the constraints to ensure long term safe operations (i.e. with the tether oscillation amplitudes below certain limits). In this paper we consider this issue referring for the lateral oscillations of a flexible tether. We refer to a bare conducting tether with the current to the various tether elements calculated from plasma theory. In addition, we impose a time variation of the current and model the response to changes in ionospheric density.

This report focuses on active experiments in space as well as laboratory experiments which are directly related to space phenomena. The active experiments involve particle releases in the CRESS and AMPTE missions. Unexpected results such as the motion of the plasma triggered several interesting computer simulations and a laboratory experiment which will be reviewed. Critical Ionization Phenomena will be discussed in this context. A recent release over Arecibo was used to create a “plasma lens” to focus radiation from the HF heater beam. The higher power triggered several nonlinear processes. Advances in plasma sources and diagnostics have made it possible to scale many laboratory experiments. Discussed here are experiments on Alfven waves generated by a localized source, 3D magnetic field line reconnection, three dimensional magnetized double layers and simulations of a tethered satellite.

The Tethered-Satellite System (TSS) was developed to provide the capability of deploying satellites on long, gravity-gradient-stabilized tethers from the Space Shuttle. Although TSS-1 achieved only limited results because deployment was terminated at a distance of only 268 m, it did conclusively show that the basic concept of long gravity-gradient-stabilized tethers is sound, and it provided a unique set of data that will contribute significantly to future missions. In this context, it is important that the configuration, instrumentation, and results of the TSS-1 mission be documented. Here, we provide a brief overview of the TSS, the organization of its instrumentation, and its operations during TSS-1. Detailed descriptions of the various investigations and their specific instrumentation and measurement capabilities are given in the papers that follow.

The Shuttle Electrodynamic Tether System (SETS) experiment formed part of the scientific experiments comprising the first flight of the NASA/ASI Tethered-Satellite System flown at an altitude of 300 km and an orbital inclination of 28.5 degrees in July–August 1992. The SETS experiment was designed to study electrodynamic behavior of the Orbiter-Tether-Satellite system as well as provide background measurements of the ionospheric environment near the Orbiter. The SETS experiment was able to operate continuously during the mission providing a large data set. Details of the SETS objectives, its instrumentation, and initial results from the mission highlighting voltage, current, and charging measurements are presented here.

This paper describes the RETE (Research on Electrodynamic Tether Effects) experiment mounted on board the TSS (Tethered-Satellite System) satellite which was deployed on a cable from the space Shuttle Atlantis during the TSS mission flown in August 1992. The experiment layout and its modes of operation are described in detail. To give an idea of RETE capabilities and actual performance during the mission, samples of measurements are also presented.

The first Tethered-Satellite System (TSS-1) Electrodynamic mission has been launched aboard the Space Shuttle STS-46 on July 31, 1992, as a joint mission between the United States and Italy. A 500 kg, spherical Satellite (1.6 m diameter), attached to the Orbiter by a thin (0.24 cm), conducting, insulated wire (Tether), has been reeled upwards from the Orbiter payload bay to a distance of 256 m, rather than the expected 20 km, when the Shuttle was at a projected altitude of 300 km. ASI, the Italian Space Agency, had the responsibility for developing the reusable Satellite, while NASA had the responsibility for developing the Deployer system and the Tether, integrating the payload and providing transportation into space. One of the main scientific goals of this first mission is to demonstrate the possibility of energy conversion from mechanical to electrical by using a long Tether orbiting through the Earth's magnetic field. ASI designed and developed an active experiment, referred to as Core Equipment, in order to carry out this demonstration, and to support all the scientific investigations related to the study of the TSS electrodynamic interactions with the Earth's ionosphere. The experiment uses two Electron Generator Assemblies (EGAs), located on the Orbiter, to re-emit into the ionosphere, as an electron beam, the electrons collected on the Satellite from the ionosphere. Other instruments provide current, voltage, and ambient pressure measurements, and allow, via a series of switches, different electrical configurations of the TSS. The Core Equipment was innovative for space experiments in general and Shuttle experiments in particular. In fact, it was the first flight in which the Shuttle has been used as an integral part of the experiment and not only as an observing platform. It was the first mission with an integrated approach to science, will all the instrumentation and their operative modes selected to characterize the electric properties of the TSS.

The first Tethered-Statellite System (TSS-1) Electrodynamic mission has been launched aboard the Space Shuttle STS-46 on July 31, 1992, as a joint mission between the United States and Italy. A 500 kg spherical Satellite (1.6 m diameter) attached to the Orbiter by a thin (0.24 cm), conducting, insulated wire (Tether), has been reeled upwards from the Orbiter payload bay to a distance of 257 m when the Shuttle was at a projected altitude of 300 km. ASI, the Italian Space Agency, had the responsibility for developing the reusable Satellite, while NASA had the responsibility for developing the Deployer system and the Tether, integrating the payload and providing transportation into space. One of the main scientific goals of this first mission was to demonstrate the possibility of energy conversion from mechanical to electrical by using a long Tether orbiting through the Earth's magnetic field. ASI designed and developed an active experiment, referred to as Core Equipment, in order to carry out this demonstration. The experiment used two Electron Generator Assemblies (EGAs), located on the Orbiter, to re-emit into the ionosphere as an electron beam the electrons collected on the Satellite from the ionosphere. Each EGA had the capability to emit an electron beam with a programmed intensity from 10 mA up to 750 mA with a resolution of 3 mA. The perveance of each EGA was 7.2 microperv, and the beam energy, up to 3 kV, was provided as part of the e.m.f. induced across the TSS due to its motion through the Earth's magnetic field. Other instruments provided current, voltage, and ambient-pressure measurements, and allowed, via a series of switches, different electrical configurations of the TSS. Moreover, the Core Equipment provided a dynamic package, to study the TSS dynamics, as a first goal, and to verify the possibility of using the TSS Satellite as a platform for future experiments in the microgravity field. The expected voltage across the TSS was estimated to be 5 kV for a full Tether deployment of 20 km. During the mission, and due to unforeseenable reasons, the Tether deployment achieved was only of 257 m. Despite this limitation, there is evidence that the experiment was working nominally in the very low-voltage range across the TSS. This result strongly increases the confidence in the possibility of high-voltage operation of the electrodynamic TSS, as the Tether deployment will achieve the 20 km, as expected in the future reflight. The paper describes the experiment, and reports some preliminary results achieved during the first mission.

A short presentation is given of the basic physical principle of a Tethered-Satellite System. The motion equations are summarized. A variety of physical phenomena in the upper atmosphere and ionosphere, as well as related to geomagnetism and gravity field will benefit by such type of missions; they are briefly illustrated and discussed. Near-term and far-term perspective applications are finally presented.

The experiment RETE was part of the payload of the mission TSS-1 flown with the Shuttle STS-46 in August 1992. In this paper we first give a brief description of the experiment and the measurements it allowed to perform. Some results are then presented on satellite charging, current in the tether and wave excitations in the satellite vicinity. Although preliminary, these data clearly point out the type of scientific investigations that will be possible with such measurements.

This paper is an overview of the project TSS-1 and of its basic electrodynamic-science objectives. To this purpose, we first discuss the electrodynamics of conducting tethers in orbit and, secondly, provide a detailed description of the project and its payload. We also add, in the final part of the paper, a short account of the first TSS-1 flight which took place in August 1992.

The authors report on the measurements performed in the IFSI/CNR plasma chamber at Frascati related to the laboratory investigation of the interaction between a plasma source and an ambient plasma of ionospheric type. Such an interaction is of relevant interest for the possibility of using electrodynamic tethered satellite systems, orbiting at ionospheric altitude, for generating electric power or propulsion in space. The interaction region was analysed at various conditions of ambient magnetic field ((0÷0.5) G) and at different polarization levels of the plasma source ((0÷40) V). The plasma measurements were carried out with a diagnostic system using an array of Langmuir probes movable in the chamber so that a map of the plasma parameters could be obtained at the different experimental conditions.

The tethered satellite system (TSS) will be accompanied by a variety of electromagnetic phenomena. An independent interconnected formation, a «tethered magnetoplasma cloud» (TMC), moving in space along the orbit of TSS, at an altitude of about 300 km, will be created. This time-dependent cloud will be a very complicated inhomogeneous formation including electromagnetic oscillations and waves of different type. Some of these waves will be observed on the Earth's surface. Rarefiel regions of the magnetoplasma behind, and dense regions in front of the shuttle orbiter (SO) and the subsatellite (SS) will arise. The neutral nitrogen beam ejected by the thruster becomes an ion beam on the day-light part of the orbit. Its energy is much greater than the local thermal energy. Instabilities of different kind as well as diffusion and recombination effects are expected to accompany the interaction of these beams with the surrounding plasma. The electron beams will produce other types of instabilities. By the electrons precessing along the magnetic-field lines, a current (5·103V, 0.5 A) should be induced in the 20th km length conducting tether. It will be closed at the bottom of the ionosphere. This huge magnetic loop, so-called «phantom loop» (PL), should accompany the tether system along its orbit. The length of this «tether electromagnetic tail» (TEMT) is about 200 km, its magnetic moment will be about 1013 A·cm2. Alfven waves and nonlinear effects of heating type may be produced by this loop along the magnetic-field lines. «Strings» of hot plasma may accompany the tether system.