A PROPELLANT-FREE PROPULION SYSTEM.

• Position: NASA will get energy from using space propulsion system with not propellant - Brief Article

NASA plans to lasso energy from the Earth's atmosphere with a tether as part of the first demonstration of a propellant-free space propulsion system, potentially leading to a revolutionary space transportation system. Scientists and engineers at NASA's Marshall Space Flight Center, Huntsville, Ala., are experimenting with tethers as part of a continuing effort to reduce the cost of space transportation dramatically. Flight demonstration of the Propulsive Small Expendable Deployer System--called ProSEDS--is scheduled for August, 2000. ProSEDS is one of the Future-X flight experiments selected by NASA to help mold the future of space transportation.

The experiment will demonstrate the use of an electrodynamic tether--basically a long, thin wire--for propulsion. An electrodynamic tether uses the same principles as electric motors in toys, appliances, and computer disk drives, as well as generators in automobiles and power plants. When a wire moves through a magnetic field, an electrical current results. The unique type of electrical circuit created by the flow of electricity through the wire results in a magnetic field that drags or pushes on an external magnetic field.

An electrodynamic tether works as a thruster because a magnetic field exerts a force on a current-carrying wire. When electrical current flows through a tether connected to a spacecraft, the force exerted on the tether by the magnetic field raises or lower's the orbit of the satellite, depending on the direction the current is flowing.

"The working principle of electrodynamic tethers...