The electrodynamic tether is an aluminum wire orbiting the Earth. Electrons are extracted from the adjacent ionosphere, enter the wire at one end, and leave it at the other end. The Earth magnetic field generates voltage in the wire. The electrodynamic tether is similar to an electric motor; it can either convert its orbital energy to electric energy (generator), or it can convert electric energy to orbital energy (propulsion). The energy is provided by solar panels. When the tether is on the dark side of the Earth, the solar panels are useless, so the tether is passive unless it has another source of energy: either a battery or a winch which transforms the tether into a flywheel. The electrodynamic tether is the most efficient when it operates in the area of the highest conductivity of the ionosphere: the altitude of 350 km and the sunny side of the Earth. The conductivity drops to 20% of the maximum value at the altitude of 1500 km. Specific thrust of the electrodynamic tether is about 0.005 N/kg. The electrodynamic tether is unstable unless it spins or is attached to a rigid structure with both ends.

Electrodynamic tether

Arcuous shape of this electrodynamic tether protects bare aluminum tracks inside the tether from the ionosphere. The tracks provide electric energy for a trolley which is not shown. When the trolley rides on the tether, it temporarily opens a slit in the tether and flattens the tether between its wheels.


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Vladimir Vasilievich Beletskii and Evgenii M. Levin, "Dynamics of Space Tether Systems," Advances in the Astronautical Sciences, Vol. 83, Univelt 1993, pp. 267-322.

Robert D. Estes, Enrico C. Lorenzini, J. Sanmartin, J. Pelaez, Manuel Martinez-Sanchez, C. L. Johnson, I. E. Vas, "Bare Tethers for Electrodynamic Spacecraft Propulsion," Journal of Spacecraft and Rockets, Vol. 37, No. 2, March-April 2000, pp. 205-211.