Oct. 8, 1999 Sports cars that speed from zero to 60 mph in four-and-a-half seconds have met their match: A new high-technology track at NASA's Marshall Space Flight Center in Huntsville, Ala., accelerates a model spacecraft from zero to 60 in less than a half-second -- with the flip of an electric switch. This magnetic levitation -- or maglev -- track will demonstrate technologies that could dramatically reduce the cost of getting to space. The Marshall Center and industry partner PRT Advanced Maglev Systems Inc. of Park Forest, Ill., have just completed installation of a 50-foot track at Marshall.
A maglev system to launch spacecraft into orbit would use magnetic fields to levitate and accelerate a vehicle along a track at very high rates of speed. Similar to high-speed trains and roller coasters that use high-strength magnets to lift and propel a vehicle a couple of inches above a guideway, a maglev launch-assist system would electromagnetically drive a space vehicle along a track. The magnetically levitated spacecraft would be accelerated at speeds up to 600 mph, and then shift to rocket engines for launch to orbit.
"The weight of propellant is a major culprit in the high cost of conventional rocket launches. But because maglev uses electricity -- an off-board energy source -- for launch assist," said Sherry Buschmann, manager of the Marshall Center's launch technologies, "the weight of the vehicle at liftoff is about 20 percent less than a typical rocket, resulting in tremendous savings in the cost of getting to space.
"Electricity is both inexpensive and environmentally safe. Each launch using a full-scale maglev track would consume only about $75 worth of electricity in today's market," said Buschmann.
The new, experimental track at Marshall is an advanced linear induction motor. Induction motors are common in fans, power drills and sewing machines, but instead of spinning in a circular motion to turn a shaft or gears, a linear induction motor produces thrust in a straight line. It's basically a rotary motor split in half and rolled out flat.
When the coils of the linear induction motor are energized by alternating current, a magnetic field is created, providing thrust that pushes an aluminum carrier along the maglev track. A horseshoe-shaped carrier containing a 5-foot, 30-pound spacecraft model is levitated about one-half inch above the track as it accelerates at six times the force of gravity.
The track -- 50 feet long, about 2 feet wide and about 1.5 feet high -- is mounted on concrete pedestals. It consists of 10 identical, 5-foot-long segments that weigh about 500 pounds each. Most of the weight is iron used in the motor. The track is shrouded with nonmagnetic stainless steel.
Magnetic levitation of the carrier and its vehicle on the track requires about 200 kilovolt amps of electricity -- the equivalent of turning on 2,000 100-watt light bulbs at one time.
Experiments to validate the concept have been conducted successfully on a 20-foot electromagnetic track at the University of Sussex in Brighton, England. Through demonstrations on Marshall Center's track, NASA seeks to learn more about aerodynamics, magnetic fields and energy storage devices associated with maglev.
"This new track will help to determine if maglev technologies offer a realistic alternative for reducing the cost of access to space, to help open the door to commercialization and exploration of space," said Buschmann.
A demonstration track measuring 400 feet is planned at Marshall within the next year. "We've known that linear induction motors can produce thrust," said Bill Jacobs, maglev lead engineer at Marshall. "Now, with larger-scale experiments, we want to demonstrate that control can be maintained at high speeds along the maglev track. To limit energy use, we are evaluating methods for distributing power to small sections of the track at a time."
In addition to industry partner PRT, NASA is joining with Lawrence Livermore National Laboratory of San Francisco to develop maglev technologies. The Livermore team is building a track that uses permanent magnets and a linear motor that runs without superconductors or complex feedback circuits.
Maglev is one of many technologies being developed by the Marshall Center's Advanced Space Transportation Program to reduce the cost of getting to space from today's $10,000 per pound to only hundreds of dollars per pound.
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