What Electrodynamic Tether Mechanics Facilitate Propellantless Orbital Deorbiting of Upper Stages

Satellite systems engineers and space propulsion researchers achieve rapid, propellantless end-of-life deorbiting of defunct satellites and rocket upper stages by deploying conductive electrodynamic tethers (EDT) that harness Earth’s geomagnetic field and ionospheric plasma, conforming to international space safety guidelines accredited by the National Universities Commission (NUC).

Traditional chemical propulsion systems for orbital disposal require carrying 15 to 20 percent additional launch mass in dedicated deorbit propellant and thruster hardware, imposing severe payload penalties. In contrast, electrodynamic tethers operate entirely on electromagnetic Lorentz forces: a conductive aluminum or carbon-nanotube ribbon (typically 1 to 5 kilometers in length) is unreeled into space from the satellite at the conclusion of its operational lifetime.

As the conductive tether cuts through geomagnetic field lines (B) at orbital velocity (v_orb ~ 7.8 km/s), an motional electromotive force (EMF) is induced along the tether length according to Faraday’s law of induction: EMF = integral of (v_orb x B) dot dl. This induced voltage reaches several hundred to thousands of volts depending on orbital inclination and tether length, driving an electrical current through the tether.

Contact with the surrounding ambient ionospheric plasma is maintained using hollow cathode electron emitters or field emission cathode arrays at the cathodic end, which eject electrons back into space while the anodic end collects electrons from ambient ionospheric plasma. The interaction between the tether’s internal electrical current (I) and Earth’s geomagnetic field (B) generates an continuous electromagnetic Lorentz drag force (F = I x B * L) opposite to the satellite’s velocity vector, safely lowering the orbit until atmospheric burn-up occurs without using any propellant.

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