Tech Briefs

A document describes a prototype of electrically conductive tethers to be used primarily to decelerate spacecraft and/or generate electric power for the spacecraft. Like prior such tethers, this tether is designed so that when it is deployed from a spacecraft in orbit, its motion across the terrestrial magnetic field induces an electric current. The Lorentz force on the current decelerates the spacecraft. Optionally, the current can be exploited to convert some orbital kinetic energy to electric energy for spacecraft systems. Whereas the conductive portions of prior such tethers are covered with electrical insulation except for end electrodes that make contact with the ionosphere, this tether includes a conductive portion that is insulated along part of its length but deliberately left bare along a substantial remaining portion of its length to make contact with the ionosphere. The conductive portions of the tether are made of coated thin aluminum wires wrapped around strong, lightweight aromatic polyamide braids. The main advantages of the present partly-bare-tether design over the prior all-insulated-tether design include greater resistance to degradation by the impact of monatomic oxygen at orbital altitude and speed and greater efficiency in collecting electrons from the ionosphere.

This work was done by Les Johnson, Jason Vaughn, Ken Welzyn, and Judy Ballance of Marshall Space Flight Center; Joe Carroll of Tether Applications; Enrico Lorenzini and Bob Estes of the Smithsonian Astrophysical Observatory; Pete Schuler, Hamid “Bob” Mojazza, and John Lennhoff of Triton Systems; and Kai Shen Hwang of Computer Sciences Corp. For further information, access the Technical Support Package (TSP) free on-line at under the Mechanics category.

This invention is owned by NASA, and a patent application has been filed. For further information, contact Sammy Nabors, MSFC Commercialization Assistance Lead, at This email address is being protected from spambots. You need JavaScript enabled to view it..

Refer to MFS-31490-1.

This Brief includes a Technical Support Package (TSP).

Bare Conductive Tether for Decelerating a Spacecraft (reference MFS-31490-1) is currently available for download from the TSP library.

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