Fast track.

All aboard the "Maglev Express"--the world's fastest train, propelled through the air by magnets!

What's sleek as a bullet and zooms through the air at 550 km/h (342 mph)? Not a bird, a plane, or even Superman. It's a Japanese train! And it set the record as the world's fastest train on Dec. 24, 1997.

The three-car vehicle, called maglev--short for magnetic levitation train--hit its peak speed on an 18-kilometer (11-mile) test track west of Tokyo. Unlike conventional trains that grind steel wheels on steel tracks, the maglev train actually levitates--yes, floats in air--10 to 15 cm (4 to 6 in.) above a track called a guideway. Powerful magnetic forces, "pushes" and "pulls" between train and guideway, lift the cars and thrust them forward.

Japanese engineers hope to extend the track some 480 km (300 mi) for a high-speed rail link between Tokyo and Osaka, Japan. The train will soar at average speeds of 500 km/h (311 mph)--almost four times as fast as an Amtrak Metroliner (see speed chart, p. 16). Within two years Germany also plans to jump on the fast track with a maglev system between Berlin and Hamburg. But here in the U.S., maglevs seem to be stalled at a snail's pace--mainly because of the pricey cost of building them. Despite its "magnetic" attraction, some American politicians remain skeptical about maglev.

REALLY REPULSIVE

To imagine the feat of a train propelled through the air, think of a flying African elephant that tips the scales at about 7,000 kg (15,400 lbs). Some maglev cars weigh more than four times as much--about 32,000 kg (70,500 lbs)!

How does maglev work? The process is repulsive. No, it won't turn your stomach. Repulsion is a property of magnetism. In the case of the maglev train, electromagnets (coils of metal wire magnetized by electric currents) on the bottom of the train repel, or push against, other electromagnets in the guideway tracks. That causes the train to float.

Here's how: The train base is equipped with superconducting electromagnets, which are chilled to frigid temperatures. When they are super-cold, superconductors conduct electricity without losing energy to resistance--a force that slows (town the flow of electricity (see diagram). In short, superconductors save energy.

Go with the flow

Electricity is the flow of electrons through a conductor, such as a metal wire. In ordinary conductors, electrons bump into atoms of the metal, slowing down the electrical flow. This slow-down is called resistance. Electrons in superconductors move in orderly pairs, so electricity flows without resistance.

The guideway's tracks and walls are also lined with wire coils. As the train moves, the superconducting electromagnets induce (create) electric currents in these wire coils, making the coils magnetic as well.

The coils create a magnetic field, the space around any magnet where you can feel its "push" or "pull." This magnetic field resists, or repels, the magnetic forces on the train. Why? Try holding the ends of two bar magnet s next, to each other. Feel a push or pull? The ends of magnets, where their magnetic power is strongest, are called poles. The poles of magnets are oriented either north or south. Know the saying "Opposites attract"? Well, the reverse is true for magnets, too: "Like poles revel." A north pole (N) repels a north pole, and a south pole (S) repels a south pole. So the magnetic forces on the train base and guideway match up in just the right way to repel each other--and levitate the train.

POWER PLAY

Hovering in thin air may seem like a great magic--or magnet--trick, but it won't get you far along a track. What propels a maglev forward at breakneck speed? For starters, maglevs run on electricity from nearby power plants, explains John Harding, a physicist at the Federal Railroad Administration in Washington, D.C.

The electricity is fed through power lines to another set of wire coils that runs the entire length of the guideway walls. These coils are part of a motor that moves the maglev by additional magnetic forces--in this case, to propel the train.

As the maglev speeds along the track, alternating electric currents that pass through each coil in the guideway walls constantly change the coil's magnetic polarity (see diagram). Electromagnets in the wall in front of the train "pull" it forward. At the same time, electromagnets behind the train "push" it forward. The effect is push, pull, push, pull. "It's like an ocean wave pushing a surfer," Harding says.

How a maglev works

To propel the train forward, an alternating current of electricity flows through coils in the guide-way walls. The current causes each coil to change its polarity (N to S; S to N) as each train magnet passes. When the train and guide-way magnets line up N-S or S-N, the result is attraction, or a "pull" forward. When the magnets line up N-N or S-S, the result is repulsion, or a "push" forward. All that pushing and pulling makes maglevs fly.

For "litcoff", electromagnets in the train's base and guideway repel each other. A north pole (N) repels N; a south pole (S) repels S. This repulsion makes the train levitate.

To make the train speed up or slow down, engineers controlling the railway increase or decrease the amount of electric power fed into the track. That changes the speed at which the magnetic wave travels underneath the train.

Some maglev trains like the one in Japan take off like jets on a runway. The train pulls out of the station on rubber wheels that retract once the train hits 160 km/h (100 mph). Then the train starts to levitate. The wheels drop down again when the train comes to a stop in the next station. (The German system remains levitated at all speeds, including zero.)

One reason maglevs "fly" so fast is that they move on a cushion of air. They're not limited by friction (rubbing action) with the track, which slows down regular railroads. They're also built with lightweight materials, like fiberglass and aluminum, instead of steel. And their bullet-shaped design helps cut down on air resistance, the force of air pushing back against the train.

MIGHTY MAGLEV

The most obvious advantage of a maglev train is its incredible speed. If maglev replaced a standard Amtrak train, it could cut a four-hour trip between New York and Boston to about one hour. "That's better than air travel. You don't have to deal with busy airports," Harding says. Maglev could also reduce congested roads and highways. More drivers might leave their wheels behind.

With such advantages, why doesn't the U.S. climb aboard the maglev express? After all, maglev science isn't new--two American scientists invented it in the early 1960s. The main drawback isn't mechanics--it's money. The Federal Railroad Administration predicts that building a maglev system in the U.S. would cost about $30 million per mile! A standard high-speed system like the Train a Grande Vitesse (TGV) in France costs about half that amount.

What makes maglev so pricey? To build a new rail line, an agency or government needs to buy land, lay down connections to power plants, construct the guideway and train, pay workers, and supply maintenance. But at least one maglev advocate is trying to fire up public interest. Tony Morris, president of American Maglev Technology, plans to build a demo of his maglev system using a motor on board the train instead of in the guideway. That design might, slash building costs in half. If his dream catches on, Morris hopes to erect a maglev line between Richmond, Virginia, and Washington, D.C., in the next century.

THINK ABOUT IT

Morris may have some future competition from students at Wallkill Middle School in Wallkill, New York. Each May, 300 kids build their own maglev trains and race them on a magnetic track. The best designs win the regional contest. Last year, Cheryl Baker, 16, grabbed a prize for her maglev shaped like a flying saucer with flashing lights. Adam Bosch, 15, won for his wind-powered maglev car with sails cut from file folders!

Think it over:

1. If your school had a maglev race, what materials would you use to build a train?

2. How would you make it float above a track and propel it forward? (Think about propulsion systems like balloons, rubber bands, electric motors, etc.)

3. Could the area where you live benefit from maglev train systems? Why or why not?

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