ABOUT ELECTRODYNAMIC TETHER, ITS STABILIZATION, ITS ADVANTAGES. In an “electrodynamic tether drag” system, such as the Terminator Tether, the tether can be used to reduce the orbit of the spacecraft to which it is attached. The motion of the long conducting wire of a tethered satellite across the geomagnetic field creates an emf of about – V/m along the length of the tether.

Author: Nizshura Kigami
Country: Andorra
Language: English (Spanish)
Genre: Politics
Published (Last): 20 December 2017
Pages: 349
PDF File Size: 15.12 Mb
ePub File Size: 18.72 Mb
ISBN: 991-9-73609-196-5
Downloads: 77638
Price: Free* [*Free Regsitration Required]
Uploader: Vudohn

In reverse the EDT system could be used for acceleration.

Electrodynamic tether

As discussed, this method of creating electrical power has a serious side-effect, namely, that the spacecraft or satellite will experience drag. In an “electrodynamic tether drag” system, such as the Terminator Tether, the tether can be used to reduce the orbit of the spacecraft to which it is attached.

This equation is called the Richardson-Dushman or Richardson equation. Many of the ionized xenon atoms are accelerated into trther walls where their energy maintains the thermionic emission temperature.

The first layer is a positive layer at the edge of the high potential plasma the contactor plasma cloud. The gravity gradient field also known tetber the “tidal force” will tend to orient the tether in a vertical position. Since it takes a much greater potential difference to collect an equivalent amount of ion current for a given areathe total current in the tether is reduced by a smaller amount.

For further information on an electrodynamic tether system customized for your spacecraft application, please contact TUI at info tethers. A power supply is elecrodynamic to the tether system and used to drive current in the direction opposite opposing the motion-induced EMFthe tether can “push” against the Earth’s magnetic field to raise the spacecraft’s orbit.

Eletcrodynamic, before the break, TSS-1R demonstrated that a satellite at a high positive potential could collect an anomalously large electron current.

You may remember from high school physics that when you move a conducting wire through a magnetic field, a voltage is induced along the wire. In terms of energy, the kinetic “movement” energy of the satellite and tether system orbiting around Earth is converted into electric energy.

To make this useful, we need to have an electric current, which means we need electrons going in at one end of the tether and getting out at the other end, being driven through the wire by the voltage. EFN is the electric field that exists between the electron emissive tip and the positively biased structure drawing the electrons out.

The tether’s far end can be left bare, making electrical contact with the ionosphere.


This occurs through devices such as a hollow cathode plasma contactors, thermionic cathodesand field emitter arrays. It can be seen in the below chart what a typical I-V curve looks like for a eleftrodynamic cathode in electron emission mode.

Such a concept would remove the current problems in finding a suitable power source, and propellant for missions to Jupiter. An important note concerning an EDT derivation pertains to the celestial body which the tether system orbits.

Electrodynamic Tethers: Getting into the Swing

An EDT takes advantage of two basic principles of electromagnetism: They are often modeled as solid endbodies, except they are a small percentage of the solid spheres surface area.

Matloff, Less Johnson, February, Much has to be learned about the interactions between the sheath structure, the geometry of the mesh, the size of the endbody, and its relation to current collection. It can be used either to accelerate or brake an orbiting spacecraft. If you carried more fuel, doing the first one is more expensive in fuel terms. Thanks to yet another alert reader for the scoop on this story. While it is not a colorful as the Rasta space tug from William Gibson ‘s Neuromancerit could provide a technology that takes low-flying satellites to a new level.

That is, it will slow down and seek a lower orbit, eventually crashing on the planet. Given a certain eletrodynamic geometry the ring in the figure above that the electrons exit throughion flow rate, and Vp, the I-V profile can be determined. Note that the velocity used in this equation is the orbital velocity of the tether. Understanding electron and ion current collection to and from the surrounding ambient plasma is critical for most EDT systems.

Electrodynmic below figure displays the drag effects an EDT system will encounter for a typical orbit.

Electrodynamic Tether / ACT / ESA

The coordinates are the first thing that must be identified. The board concluded that after arcing had burned through most of the Kevlar, the few remaining strands were not enough to withstand forces being exerted by satellite deployment Porous endbodies have been proposed as a way to reduce the drag of a collecting endbody while ideally maintaining a similar current collection.

The arcing occurred because either external foreign object penetration but not orbital debris or micrometeoroids or a defect in the tether caused a breach in the layer of insulation surrounding the tether conductor. At a voltage of V, the TSS-1R tether leaked gas into its deployer control reel enclosures and the elevated neutral pressure led to Paschen discharge and loss of the mission.

The middle section contains a gaseous nitrogen tank that will fuel the 12 low powered thrusters that will propel the satellite during deployment above the orbiter. An early experiment used a meter conducting tether. The Tethered Satellite System TSS will deploy and retrieve a satellite from the Space Shuttle orbiter with a tether of up to km in length attached between the satellite and the orbiter.


The boost mode is similar to the de-orbit mode, except for the fact that a High Voltage Power Supply HVPS is also inserted in series with the tether system between the tether and the higher positive potential end.

This enormous bias eventually led to a continuous arc on the tether see The Continuous Arc, section 4.

TUI: Engineering the Future

By using the space environment to create thrust, electrodynamic tether systems can dramatically reduce the cost of tethfr space missions by eliminating the need to launch large quantities of propellant into orbit. Energy generation is achieved at the expense of kinetic energy of the spacecraft.

Equally the power produced by radioisotope thermal generators may be insufficient for the mission requirements. Improved methods include creating an electron emitter, such as a thermionic cathodeplasma cathode, plasma contactor, or field electron emission device.

Its objectives on this flight are to demonstrate the ability to deploy and control satellites on long tethers in space and to conduct space plasma experiments that include the generation of electrical power. The electron and ion collection at the end-body is governed by the thermal collection process, which is given by Ithe and Ithi. This effect then has a chance to cause the libration amplitudes to grow and eventually cause wild oscillations, including one such as the ‘skip-rope effect’, [67] but that is beyond the scope of this derivation.

An electrodynamic tether EDT is a simple idea, but one with an amazing number electroeynamic uses. In this fashion, the voltage that is electromagnetically induced within the tether can cause current to flow through the surrounding space environmentcompleting an electrical circuit through what appears to be, at first glance, an open circuit.

At the end of a satellite’s life or a rocket stage, or anything elseit is given a signal to release a long wire antenna. These are potentially huge benefits, but electrodynamic tether systems eelctrodynamic work when orbiting within a sufficiently strong magnetic field.

The only reason a tether picks up electrons is so the current elecrodynamic wire runs in one direction. In the contactor plasma, the electron density is approximately equal to the ion density. Set it up so the force opposes motion and the craft loses energy and descends.