______________________________________________________________________________ | File Name : MEISSNER.ASC | Online Date : 07/08/95 | | Contributed by : Jerry Decker | Dir Category : GRAVITY | | From : KeelyNet BBS | DataLine : (214) 324-3501 | | A FREE Alternative Sciences BBS sponsored by Vanguard Sciences | | KeelyNet * PO BOX 870716 * Mesquite, Texas * USA * 75187 | | Voice/FAX : (214) 324-8741 InterNet - keelynet@ix.netcom.com | | WWW Mirror - http://www.eskimo.com/~billb | |----------------------------------------------------------------------------| This is one of the better articles I've seen on superconductivity because it relates to the field of practical levitation. Other applications of course have to do with energy or information storage and transmission. About a year ago, one of our group had spoken to an inventor named Herb Wachspress out in California. He has developed a flying device that he demonstrates for $5000. That is because it uses superconducting phenomena to provide lift AGAINST THE EARTHS' MAGNETIC FIELD and flies off into space each time. The patent for his 'Free-Flying Levitator' is listed on KeelyNet as WACHSPRE.ASC. ------------------------------------------------------------------------------ From the New York Times Dreams of Levitation A physicist imagines that he is momentarily annoyed by the big conference table occupying the middle of his office. He gives it a shove with one hand, and, in his imagination, it floats away, drifting lazily toward the corner, until finally it stops with a bump against the wall. So it might, in a speculative future. For now, the physicist, Praveen Chaudbari, vice president for science at the International Business Machines Corporation, is engaging in a reverie about superconductivity and its most bizarre by-product: the phenomenon of levitation, science's answer to the flying carpet, "You don't even have to make cars," he says. "You could make little gizmos, you could put on a pair of special shoes and make little tracks along which you as a human being could push yourself and keep going. Nothing to stop you, right? I see the whole transportation system being very different. At airports, instead of these long conveyor belts we have, you could get onto one of these platforms that are levitating and just stay on it while it takes you around." Levitation is not just the strangest but also one of the most practical prospects raised by the recent boom in superconducting materials. Floating trains, floating furniture, floating toys, floating people - otherwise sober scientists are talking about applications that used to belong to the realm of science fiction. They are amused, but they are serious. If the new materials fulfill their early promise, and especially if a room-temperature version can be made practical, the ability to lift objects off the ground and free them from mechanical friction could bring suprising rewards. Levitation comes from a property of superconductors only indirectly related to the property that gives them their name: the ability to carry electric current without any loss due to resistance. With or without electric current, a chunk of superconductor placed above a magnet settles calmly in midair. For that matter, a chunk of magnet placed above a superconductor also hangs in the air - levitation works either way. The superconductor has the peculiar property of pushing out any external magnetic field, so the magnet cannot approach. It just hovers, in the soft grip of an invisible hand. The phenomenon has a certain built-in measure of stability. "Levitation means that your piece of metal sits on a magnetic pillow," says Vladimir Z. Kresin of the Lawrence Berkeley Laboratory in Berkeley, California. "You can move right, left, forward, back - because of the configuration of the magnetic field, you have a real equilibrium position in the center. It's a system trying to keep everything in the middle." Any mechanical device that requires bearings - any device, for example, in which something must rotate at high speed, like a generating turbine or a gyroscope - could use levitation to eliminate friction. Friction typically sets the limit on the speed of rotation, and it also produces waste heat that must be drawn away. Scientists have let themselves fantasize about levitation for decades. Twenty-two years have passed since a Stanford physicist, William A. Little, writing in SCIENTIFIC AMERICAN, proposed not only superconducting hovercraft but also a sort of physicist's theme park, with people "riding on magnetic skis down superconducting slopes and ski jumps." To date, the single real- world anchor for such whimsy is the levitating train, a transportation system whose feasibility has been demonstrated by a Japanese National Railways prototype. The experimental trains carry powerful superconducting magnets, cooled, expensively, by liquid helium. Smaller-scale, less expensive technologies await superconductors that require less cooling, and such superconductors have been found in a series of recent breakthroughs that have brought superconductivity out of the shadows of scientific esoterica. A new class of materials, easy to duplicate and inexpensive to produce, makes the sudden transition to superconductivity at record high temperatures, though still several hundred degrees below zero. Those materials, requiring cooling by liquid nitrogen, are enough to make possible such non-floating applications as highly efficient long-distance transmission lines and fast, small supercomputers, applications and vast commercial promise. But another class of applications - the kind that would transform a host of ordinary, visible aspects of everyday life - demands a superconductor that would require no refrigeration at all. Physicists have been reporting signs of this elusive new room-temperature superconductor, seemingly making itself felt in several different laboratories, though still impossible to isolate and stabilize. So scientists are allowing themselves to hope that the room- temperature superconductor will become a reality, and they are thinking more seriously than ever about a world in which objects could be made to float. "If it's going to come into society, you could think of assembly lines, guiding materials around in this innovative way," says Theodore Geballe of Stanford University. Personal transportation could be freed from two dimensions, especially in cities, "where you get gridlock," he said. "You could just go into three dimensions with small, guided transportation, not the big levitated trains." Metal tracks would have to be built at different levels, floating people along. The capital cost would be considerable, and the temptation to slide through the air at unsafe speeds could be a serious concern. Propulsion might involve magnets, air jets, or muscle power - in any case, starting and stopping would be nontrivial engineering problems, as would the question of air-traffic control. The consequences of making powerful magnets a ubiquitious feature of everyday life are far from obvious. In terms of pure science, however, the fundamental principles are well understood. Levitation begins with the fact that a magnetic field creates a current in any conducting material - the principle at work in electrical generators. A current creates its own magnetic field - the principle of work in electric motors. But superconductors are special. If a magnetic field penetrated a superconductor, it would create a current that would set up exactly the opposite field. Wherever the magnet moved and however it was oriented, it would see its ghostly counterpart below, repelling it. So the external field CANNOT penetrate - it is expelled, an effect known as the Meissner field. Even on the small scale of the laboratory, the results are uncanny. A piece of flat iron magnet sits on a table. A chunk of the new superconducting material, a dull gray ceramic, is dipped into a Styrofoam cup full of liquid nitrogen to cool it. Then the superconductor is put above the magnet, where it floats. It can be poked, spun, and nudged from place to place, but it remains suspended until it warms up. Then, making the transition from superconductor to ordinary ceramic, it settles to the ground. The technology designed for high-speed trains uses a variation of the physics of levitation, set in motion. The train is equipped with superconducting magnets, coils of wire that become magnetic when a current is passed through them. Because there is no resistance to electricity, the current does not need to be maintained with a continuous power supply. Once it is started, it continues forever. The train sits on a track of ordinary metal, such as aluminum. As long as it is motionless, it just sits, but when it begins moving forward, the magnets induce a current in the aluminum, setting up another repulsive magnetic field. The effect is instantaneous and short- lived. "The magnet in the vehhicle has to think it sees an equal and opposite magnet down below," Dr. Geballe says, "A few milliseconds, that's enough time. Then you move on to a virgin piece of aluminum." The train starts on wheels and then, at about fifteen miles an hour, lifts off the ground. For forward propulsion, the train relies on separate magnets embedded in the track. In case of a complete power failure, the train would simply settle gradually down onto its wheels. The Department of Transportation investigated levitating trains, among other futuristic transportation ideas, a decade ago, but interest waned, in part because the United States, with its spread of urban areas and its love of private automobiles, seems less than ideally suited for large-scale rail transport. Some scientists complain that the federal government has long been too reluctant to support research into innovative technologies of transport. The Japanese, however, went ahead with a program of trains using superconducting magnets, while West Germany sponsored an experimental train using a different magnetic technology. As a result, much of the engineering has already been done. "It's entirely feasible - the Japanese and the Germans could implement it right away," says Francis C. Moon, chairman of the department of theoretical and applied mechanics at Cornell University. Dr. Moon conducted research on the stability of levitating trains and observed tests of the Japanese prototype, flying six to eight inches above its track at speeds of two hundred to three hundred miles per hour. Track wear and tear is not a problem; nor is noise. "The train goes by in a whisper," he says. "It's weird to see." Years of imagination and hard engineering have gone into the levitating train. The next generation of levitating objects can only be guessed at. But design work and engineering calculations have also been applied to the problem of replacing bearings with superconducting magnets. In an engine or turbine where one ring rotates inside another, the principle would be the same as in a levitating train. Less industrially, Dr. Chaudhari's floating furniture would be guided by wires embedded in the floor, he suggested. To allow a table or chair to rise and sink, designers could use small electromagnets that could be controlled with a handy dial. "It just pops up," he said. "The strength will determine how high or low it goes." Others, when they witness levitation, cannot help but think of toys. "It's funny by itself," said Dr. Kresin of Lawrence Berkeley Laboratory. "Maybe one application will be for the toy industry. You can apply huge fantasy using these principles." > JG ------------------------------------------------------------------------------