Swords to plowshares – or trains – magnetic propulsion system adapted from Star Wars defense program could propel trains along modified existing rails – Brief Article
IN THE LATE 1980s ENGINEERS AT Sandia National Laboratories tackled one of the most vexing headaches of the controversial Star Wars program: how to quickly and at a reasonable price launch killer satellites that could shield America from nuclear attack. One idea was to build a half-mile-long “coil gun” that would hurl satellites into orbit using pulsed magnetic fields. Now that the cold war is over, the Sandia researchers have refashioned their system for a more benign purpose: magnetically powered trams.
Magnetically levitated train prototypes have been around for 20 years or so, and one in Japan has reached speeds exceeding 320 miles per hour. But “maglev” trains have yet to really catch on, in part because they require the construction of a whole new track network–and a very expensive one at that. The magnetic coils that drive maglev trains are located in the tracks themselves–the train floats passively, carried along by magnetic pulses–and building and operating hundreds of miles of electrically powered coils costs a bundle
The Sandia system, dubbed Seraphim (for Segmented Rail Phased Induction Motor), is different. It doesn’t levitate: it has wheels and rolls on rails like conventional trains. And unlike maglev trains, a Seraphim train would carry its own motor–magnetic coils powered by an onboard gas-turbine generator. That means it could run on existing tracks modified to include a series of small, three-foot-long aluminum plates attached to the rails at three-foot intervals. Electric currents surging through the train’s coils would induce electric currents in the plates; the magnetic field created by the latter would oppose the magnetic field of the former, thus pushing the train along.
Recent tests of the system have accelerated a laboratory model to 34 miles per hour on 12 feet of track, say s project leader Barry Marder, a physicist. There are still some problems to be worked out, though. The most serious is to find a way to shield the magnetic coils, which would produce fields powerful enough to disturb appliances in any homes built near the tracks.
Marder is optimistic that such problems will be overcome. A full-scale system, he says, could reach speeds of 200 miles per hour on upgraded conventional tracks or 300 miles per hour on specially designed tracks. Conventional trains can’t reach such speeds efficiently because their wheels drive the train, and some power is wasted when the wheels lose traction and slip along the rails. That doesn’t happen with the Sandia train, says Marder, because the wheels merely guide the train along the rails. “In our system, all the power you have can go into propulsion. You’re not going to spin your wheels.”
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