A Grid-Sphere Electrode for Tether Current Collection

The Grid-Sphere is a passive electrode contactor that relies on a very large area to allow the collection of large currents from the ionosphere. Dynamic drag is minimized by using a grid construction. This Grid-Sphere can provide electrodynamic tethers with the ability to passively collect arbitrarily large currents at the positive pole?requiring only low bias voltages. This makes current collection independent of tether length and eliminates hazardous high-voltage operations. The Phase-1 results include the development of grid-film materials with the required characteristics and the derivation of a linearized model of the current collection process?and clearly show the Grid-Sphere to be feasible and to collect current with virtually the same efficiency as a solid-surface spherical electrode of the same radius.