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A space tether is a long cable used to couple spacecraft together as they orbit the central body i. Tethers are usually made of thin strands of high-strength fibers such as Spectra or Kevlar. Any space tethered system is intimately connected to the gravitational force field. Conducting tethers offer the additional capability to interact with the magnetic and electrical force fields.
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- Can a Cryptocurrency Self-Regulatory Organization Work? Assessing Its Promise and Likely Challenges
- History of the Tether Concept and Tether Missions: A Review
- Polymers application in proton exchange membranes for fuel cells (PEMFCs)
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Can a Cryptocurrency Self-Regulatory Organization Work? Assessing Its Promise and Likely Challenges
This paper introduces history of space tethers, including tether concepts and tether missions, and attempts to provide a source of references for historical understanding of space tethers. Several concepts of space tethers since the original concept has been conceived are listed in the literature, as well as a summary of interesting applications, and a research of space tethers is given.
With the aim of implementing scientific experiments in aerospace, several space tether missions which have been delivered for aerospace application are introduced in the literature. A space tether is a kind of long cable ranging from a few hundred meters to many kilometers, which uses series of thin strands of high-strength fibre to couple spacecraft to each other or to other masses, and it also provides a mechanical connection which enables the transfer of energy and momentum from one object to the other.
Since the conception of space tether came up in the 19th century, it has not yet been fully utilised. Space tethers can be used in many applications, including the study of plasma physics and electrical generation in the upper atmosphere, the orbiting or deorbiting of space vehicles and payload, for interplanetary propulsion, and potentially for specialised missions, such as asteroid rendezvous, or in extreme form as the well-publicized space elevator. With the development of space technology, space tethers should be widely used in space exploration [ 1 ].
Space tethers have a long history since the original idea was proposed in , and research work of space tethers quickly expanded, especially the research on dynamics and control of space tethers, which are the fundamentally aspects. Furthermore, a series of tether missions have been delivered for aerospace applications in the last century. The original idea of an orbital tower was first conceived by Konstantin Tsiolkovsky in [ 6 , 7 ].
It would be supported in tension by excess centrifugal force on the part of the tower beyond geosynchronous altitude. Payloads would be transported up and down the tether without the use of any propellant. This structure would be held in tension between Earth and the counterweight in space, like a guitar string held taut. Space elevators have also sometimes been referred to as beanstalks, space bridges, space lifts, space ladders, skyhook, orbital towers, or orbital elevators [ 8 — 10 ].
The first modern concept about space elevators was proposed as a nontechnical story in by another Russian scientist, Yuri Artsutanov. He suggested using a geostationary satellite as the base from which to deploy the structure downward.
A cable would be lowered from geostationary orbit to the surface of the Earth by using a counterweight, which was extended from the satellite away from Earth, keeping the centre of gravity of the cable motionless relative to Earth. He also proposed tapering the cable thickness to ensure that the tension in the cable was constant, this gives a thin cable at ground level, thickening up towards GSO [ 11 — 13 ].
They determined what type of material would be acceptable to build a space elevator, assuming it would be a straight cable with no variations in its cross section, and found that the strength required would be twice that of any existing material including graphite, quartz, and diamond [ 13 , 15 ].
Colombo et al. The concept finally came to the attention of the space flight engineering community through a technical paper written by Pearson [ 17 ] of the air force research laboratory in He designed a tapered cross section which would be better suited to building the elevator. The whole cable would be thickest at the geostationary orbit, where the tension was greatest, and would be narrowest at the tips so as to reduce the amount of weight per unit area of cross section that any point on the cable would have to bear.
He suggested using a counterweight that would be slowly extended out to , kilometres as the lower section of the elevator was built. The upper portion of the cable would have to be longer than the lower without a large counterweight, due to the way in which gravitational and centrifugal forces change with distance from Earth.
His analysis included disturbances such as the gravitation of the Moon, wind, and moving payloads up and down the cable. The weight of the material needed to build the elevator would have required thousands of space shuttle trips, although part of the material could be transported up the elevator when a minimum strength strand reached the ground, or it could be manufactured in space from asteroids [ 7 ].
This concept was an early version of a space tether transportation system. Jerome Pearson discussed the concept of anchored lunar satellites in The Journal of the Astronautical Sciences in , in which it was observed of anchored lunar satellites that they balanced about the collinear libration points of the Earth-Moon system and attached to the lunar surface [ 19 ].
Also in , space elevators were introduced to a broader audience with the simultaneous publication of Arthur C. In , a history of these concepts and their more modest derivatives was written by Tiesenhausen [ 20 ]. Carroll conducted some studies on the advantages of swinging and barely spinning systems [ 21 , 22 ]. Since then, a series of interesting space tether applications have been proposed and analysed. Particularly in the last decade, the study of space tether has received significant attention from researchers covering a broad range of applications.
Some examples of applications have considerable promise including the deployment and retrieval of subsatellites, aerobraking, electrodynamic boost, deorbit of satellites, and momentum-transfer with libration and rotation analysis. Control research on space tether applications was one of the most important aspects of space tether study, and each control method suited each application or mission requirement, such as liberation, oscillation, attitude, motion, and deployment [ 23 ].
With the development of space technology, a series of missions have been delivered for aerospace application using tethered satellite systems over the past forty years. Many proposals were implemented including scientific experiments in the microgravity environment, upper atmospheric research, the generation of electricity, cargo transfer between orbiting bodies, collections of planetary dust, and the expansion of the geostationary orbit resource by tethered chain satellites.
A brief tether mission history and the status of each one are shown in Table 1 [ 1 , 7 , 9 , 21 , 24 — 32 ]. The major objectives were: 1 rendezvous, docking, and evaluation for the EVA; 2 tethered vehicle evaluation and experiments; 3 revolution rendezvous, docking, and automatic reentry demonstration; 4 docked maneuvering for a high-apogee excursion, docking practice, system tests, and GATV parking.
Its plan was to deploy metres of cable, but its deployed cable was about 38 metres. The TPE-2 mission was launched on 29 January, , and its tether was deployed to a distance about 65 metres [ 7 , 26 ]. As the deployment system was improved, the tether deployed to its full length of meters, and the tether was also found to act as a radio antenna for the electrical current through the cable.
This mission was designed to study the charging of an electron-beam emitting payload using a tethered mother-daughter payload configuration [ 31 , 32 ]. In , the US Air Force Geophysics Laboratory launched the Echo-7, which was designed to study the artificial electron beam propagation along magnetic field lines in space. The mission was designed to study how the artificial electron beam propagates along magnetic field lines in space [ 7 , 33 ].
The mission was to generate electromagnetic waves by modulating the electron beam. The tether was fully deployed over meters and the experiments all worked as planned [ 7 , 35 ]. The TSS-1 mission discovered a lot about the dynamics of the tethered system. Although the satellite was deployed only metres, it was able to show that the tether could be deployed, controlled, and retrieved, and that the TSS was easy to control, and even more stable than predicted. The TSS was an electrodynamic tether, its deployment mechanism jammed resulting in tether sever and less than metres of deployment.
The objectives of TSS-1 were 1 to verify the performance of the TSS equipment; 2 to study the electromagnetic interaction between the tether and the ambient space plasma; 3 to investigate the dynamical forces acting on a tethered satellite. In the first tether deployment, when the satellite was moving excessively from side to side, the deployment was aborted.
The second trial of deployment was unreeled to a length of metres [ 7 , 37 — 41 ]. The SETS experiment was designed to study the electrodynamic behaviour of the Orbiter-Tether-Satellite system, as well as to provide background measurements of the ionospheric environment near the Orbiter.
The SETS experiment was able to operate continuously during the mission thereby providing a large data set. Details of the SETS objectives, its instrumentation, and initial results from the mission highlighting voltage, current, and charging measurements were presented [ 42 ].
An early experiment used a metre conducting tether. When the tether was fully deployed during this test, it generated a potential of 3, volts. This conducting single-line tether was severed after five hours of deployment. The PMG flight demonstration proved the ability of the proposed Space Station plasma grounding techniques in maintaining the electrostatic potential between the Space Station and the surrounding plasma medium. The PMG also demonstrated the ability to use electrostatic tethers to provide thrust to offset drag in LEO space systems, and it demonstrated the use of direct magnetic nonrocket propulsion for orbital maneuvering [ 23 ].
The SEDS-2 used feedback braking, which was started early in deployment. This limited the residual swing after deployment to 4 degrees. The SEDS-2 had an improved braking system compared to SEDS-1, which was a feedback control system and applied braking force as a function of the measured speed of the unrolling tether.
This was to ensure that the satellite stopped flying out just when the whole tether was deployed and to prevent the bounces experienced during the previous mission [ 7 ]. The mission also flew the United States Microgravity Payload USMP-3 , which was designed to investigate materials science and condensed matter physics. ATEx was intended to demonstrate the deployment and survivability of a novel tether design, as well as being used for controlled libration maneuvers. The ATEx lower end mass was jettisoned from the host spacecraft and the tethered upper and lower end masses freely orbited the Earth in a demonstration of long-term tether survivability.
The ATEx was a tethered satellite experiment with the following mission objectives: 1 deployment of a novel, nonconductive polyethylene tape tether; 2 verification of dynamical models of deployment and orbital libration; 3 ejection of the ATEx lower end mass from the host spacecraft [ 47 ].
It was a real-time tracking satellite of the miniaturised picosatellite satellite series. A pair of 0. It was originally intended to be flown along with a launch of a Global Positioning System GPS satellite in the spring of , but was cancelled at the last moment, due to concerns that the tether might collide with the international space station [ 49 ].
YES2 aimed to demonstrate a tether-assisted reentry concept, whereby the payload would be returned to Earth using momentum provided from a swinging tether. Deployment was intended to take place in two phases: 1 deployment of 3.
The measured altitude gain of the Fonton-M3 corresponded with what simulations showed would have happened if The YES-2 mission was very nearly a complete success becouse of the following: 1 the entire record-breaking length of tether has been deployed; 2 Fotino rocket seemed to have been deorbited by using momentum exchange; 3 plentiful data has been gathered on tether deployment, dynamics and deorbiting, which may lead to an operational way of returning capsules without any form of propulsion [ 7 , 51 , 52 ].
The separation of the rocket and satellite and the transfer into the planned orbit were successful, but the tether—only deployed to a length of several centimeters because of the launch lock trouble of the tether reel mechanism [ 53 ]. The tether was metres long and deployed as planned, a video of deployment was transmitted to the ground. Tether deployment was verified successfully, as was the fast ignition of a hollow cathode in the space environment [ 54 ]. This experiment is currently planned for launch as a secondary payload in September TEPCE will use a passive braking to reduce speed and hence recoil at the end of electrodynamic current in either direction.
The main purpose of this mission is to raise or lower the orbit by several kilometres per day, to change libration state, to change orbit plane, and to actively maneuver [ 55 ].
This literature review has attempted to provide the interested reader with a historical review of space tethers. Two main topics in space tethers history are introduced, including tether concepts and tether missions.
As has been shown, many novel space tether concepts were proposed since the original concept of space tether was conceived. Furthermore, many related research and application studies have been presented, such as dynamics, control, and deployment of space tethers. The paper also covers a series of tether missions which have been delivered for aerospace application using tethered satellite systems.
Most of these tether missions show that space tethers are fruitful for the future development of aerospace technologies. The authors would like to acknowledge the partial supports provided by the National Natural Science Foundation of China no.
Also, the authors would like to acknowledge three anonymous reviewers for their valuable comments for this paper. This is an open access article distributed under the Creative Commons Attribution License , which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
Article of the Year Award: Outstanding research contributions of , as selected by our Chief Editors. Read the winning articles. Academic Editor: W. Received 13 Dec Accepted 16 Jan Published 14 Feb Abstract This paper introduces history of space tethers, including tether concepts and tether missions, and attempts to provide a source of references for historical understanding of space tethers.
History of the Tether Concept and Tether Missions: A Review
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Polymers application in proton exchange membranes for fuel cells (PEMFCs)
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ROLE OF GEMINI SURFACTANTS IN FIGHT AGAINST COVID19
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