A pair of carbon nanotube arrays will be flying in space by the end of the year to test technology that could provide more efficient micro-propulsion for future generations of spacecraft. Part of a Cube Satellite (CubeSat) developed by the Air Force Institute of Technology (AFIT), the arrays will support what is expected to be the first-ever space-based testing of carbon nanotubes as electron emitters.
Researchers at Georgia Tech Research Institute produced the arrays using unique technology that grows bundles of vertically aligned nanotubes embedded in silicon chips. In future versions of electricallypowered ion thrusters, electrons emitted from the carbon nanotube tips may be used to ionize a gaseous propellant such as xenon. The ionized gas would then be ejected through a nozzle to provide thrust for moving a satellite in space.
The carbon nanotube arrays are excellent conductors and their geometry makes them ideal electron emitters. Georgia Tech uses a series of deposition and etching steps to fabricate the arrays in cleanrooms. Each one-centimeter square array contains as many as 50,000 nanotube bundles, and each bundle is grown from a five-micron pit etched into the silicon.
Spacecraft are launched using chemical rockets that provide large amounts of thrust. Once in orbit, however, the vehicles can use electrically powered thrusters to change orbits or make other maneuvers.