BARE WIRE ANODES FOR ELECTRODYNAMIC TETHERS

The collection of electrons from the ionosphere is the major problem f acing high-power electrodynamic tethers. This article discusses a simp le electron-collection concept which is free of most of the physical u ncertainties associated with plasma contactors in the rarefied, magnet ized environment of an orbiting tether. The idea is to leave exposed a fraction of the tether length near its anodic end, such that, when a positive bias develops locally with respect to the ambient plasma, and for a tether radius small compared with both thermal gyroradius and D ebye length, electrons are collected in an orbital-motion-limited regi me. It is shown that large currents can be drawn in this way with only moderate voltage drops. The concept is illustrated through a discussi on of performance characteristics for generators and thrusters.