Better electric propulsion may boost satellite lifetimes

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Washington, October 25 (ANI): Researchers at the Georgia Institute of Technology are all set to develop improved components that will boost the efficiency of electric propulsion systems that are used to control the positions and lifetimes of satellites and planetary probes.

Focusing on improved cathodes for devices known as Hall effect thrusters, the research would reduce propellant consumption in commercial, government and military satellites, allowing them to remain in orbit longer, be launched on smaller or cheaper rockets, or carry larger payloads.

Sponsored by the U.S. Defense Advanced Research Projects Agency Defense Sciences Office (DARPA-DSO), the 18-month project seeks to demonstrate the use of propellant-less cathodes with Hall effect thrusters.

"About 10 percent of the propellant carried into space on satellites that use an electric propulsion system is essentially wasted in the hollow cathode that is part of the system," said Mitchell Walker, an assistant professor in Georgia Tech's School of Aerospace Engineering and the project's principal investigator.

"Using field emission rather than a hollow cathode, we are able to pull electrons from cathode arrays made from carbon nanotubes without wasting propellant. That will extend the life of the vehicle by more efficiently using the limited on-board propellant for its intended purpose of propulsion," Walker added.

To maintain their positions in space or to reorient themselves, satellites must use small thrusters that are either chemically or electrically powered.

Electrically-powered thrusters use electrons to ionize an inert gas such as xenon. The resulting ions are then ejected from the device to generate thrust.

In existing Hall effect thrusters, a single high-temperature cathode generates the electrons.

A portion of the propellant - typically about 10 percent of the limited supply carried by the satellite - is used as a working fluid in the traditional hollow cathode.

The DARPA-funded research would replace the hollow cathode with an array of field-effect cathodes fabricated from bundles of multi-walled carbon nanotubes.

Powered by on-board batteries and photovoltaic systems on the satellite, the arrays would operate at low power to produce electrons without consuming propellant.

In addition to reducing propellant consumption, use of carbon nanotube cathode arrays could improve reliability by replacing the single cathode now used in the thrusters.

Before the carbon nanotube cathodes developed by Georgia Tech can be used on satellites, however, their lifetime will have to be increased to match that of a satellite thruster, which is typically 2,000 hours or more. (ANI)

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