Carbon Nanotube Emitters for the Mitigation of Spacecraft Charging

This proposal is to develop emitters based on carbon nanotubes to gently discharge spacecraft. These emitters require no power or gas, and could replace plasma contactors now used on spacecraft. They are based on oriented arrays of carbon nanotubes bonded to a conducting backing. Carbon nanotubes have been shown to emit with electric fields much lower than those that produce disruptive or damaging arcs, and should therefore slowly drain charge from spacecraft to avoid such arcs. However, methods of attaching the tubes to a conductive surface that are suitable for space applications have not been demonstrated. In the proposed effort, PSI will demonstrate a method for fabrication of arrays of carbon nanotubes, with the tubes aligned with their axes normal to a conductive substrate. This will minimize the field required for emission. The fabrication method, which is an extension of plating technology, will be suitable for the inexpensive production of both small and large arrays which will withstand the space environment. In Phase I, PSI will fabricate and demonstrate arrays with areas up to 10 cm2. In Phase II, the fabrication process will be optimized, and operation of the emitters tested in a simulated space environment.