If you've been to an airport lately, you've probably noticed that air travel is becoming more and more congested. Despite frequent delays, airplanes still provide the fastest way to travel hundreds or thousands of miles. Passenger air travel revolutionized the transportation industry in the last century, letting people traverse great distances in a matter of hours instead of days or weeks.
The only alternatives to airplanes -- feet, cars, buses, boats and conventional trains -- are just too slow for today's fast-paced society. However, there is a new form of transportation on the horizon that will revolutionize transportation of the 21st century the way airplanes did in the 20th century.
Photo courtesy Railway Technical Research Institute
Traveling at speeds of up to 300 mph (500 kph), maglev trains could begin connecting distant cities as soon as 2004.
At least two countries are using powerful electromagnets to develop high-speed trains, called maglev trains. Maglev is short for magnetic levitation, which means that these trains will float over a guideway using the basic principles of magnets to replace the old steel wheel and track trains. In this edition of HowStuffWorks, you will learn how electromagnetic propulsion works, how two specific types of maglev trains work and when you might be able to ride one of these trains.
If you've ever played with magnets, you know that opposite poles attract and like poles repel each other. This is the basic principle behind electromagnetic propulsion. Electromagnets are similar to other magnets in that they attract metal objects, but the magnetic pull is temporary. As you can read about in How Electromagnets Work, you can easily create a small electromagnet yourself by connecting the ends of a copper wire to the positive and negative ends of an AA, C or D-cell battery. This creates a small magnetic field. If you disconnect either end of the wire from the battery, the magnetic field is taken away.
The magnetic field created in this wire-and-battery experiment is the simple idea behind a maglev train rail system. There are three components to this system:
The big difference between a maglev train and a conventional train is that maglev trains do not have an engine -- at least not the kind of engine used to pull typical train cars along steel tracks. The engine for maglev trains is rather inconspicuous. Instead of using fossil fuels, the magnetic field created by the electrified coils in the guideway walls and the track combine to propel the train.
- A large electrical power source
- Metal coils lining a guideway or track
- Large guidance magnets attached to the underside of the train
Photos courtesy Railway Technical Research Institute
Above is an image of the guideway for the Yamanashi maglev test line in Japan. Below is an illustration that shows how the guideway works.
The magnetized coil running along the track, called a guideway, repels the large magnets on the train's undercarriage, allowing the train to levitate between 0.39 and 3.93 inches (1 to 10 cm) above the guideway. Once the train is levitated, power is supplied to the coils within the guideway walls to create a unique system of magnetic fields that pull and push the train along the guideway. The electric current supplied to the coils in the guideway walls is constantly alternating to change the polarity of the magnetized coils. This change in polarity causes the magnetic field in front of the train to pull the vehicle forward, while the magnetic field behind the train adds more forward thrust.
Maglev trains float on a cushion of air, eliminating friction. This lack of friction and the trains' aerodynamic designs allow these trains to reach unprecedented ground transportation speeds of more than 310 mph (500 kph), or twice as fast as Amtrak's fastest commuter train. In comparison, a Boeing-777 commercial airplane used for long-range flights can reach a top speed of about 490 mph (789 kph). Once manufacturers can prove that maglev trains can transport passengers safely at such high speeds, maglev trains could become an ideal alternative to airplanes. Developers say that they will likely link cities that are up to 1,000 miles (1,609 km) apart. At 310 mph, you could travel from Paris to Rome in just over two hours.
While maglev transportation was first proposed more than a century ago, the first commercial maglev train made its test debut Shanghai, China, in 2002 (click here to learn more), using the train developed by German company Transrapid International. Germany and Japan are both developing maglev train technology, and both are currently testing prototypes of their trains. Although based on similar concepts, the German and Japanese trains have distinct differences.
In Germany, engineers have developed an electromagnetic suspension (EMS) system, called Transrapid. In this system, the bottom of the train wraps around a steel guideway. Electromagnets attached to the train's undercarriage are directed up toward the guideway, which levitates the train about 1/3 of an inch (1 cm) above the guideway and keeps the train levitated even when it's not moving. Other guidance magnets embedded in the train's body keep it stable during travel. Germany has demonstrated that the Transrapid maglev train can reach 300 mph with people onboard.
Japanese engineers are developing a competing version of maglev trains that use an electrodynamic suspension (EDS) system, which is based on the repelling force of magnets.
Photo courtesy Railway Technical Research Institute
Japan's MLX01 experimental maglev train
The key difference between Japanese and German maglev trains is that the Japanese trains use super-cooled, superconducting electromagnets. This kind of electromagnet can conduct electricity even after the power supply has been shut off. In the EMS system, which uses standard electromagnets, the coils only conduct electricity when a power supply is present. By chilling the coils at frigid temperatures, Japan's system saves energy.
Another difference between the systems is that the Japanese trains levitate nearly 4 inches (10 cm) above the guideway. One potential drawback in using the EDS system is that maglev trains must roll on rubber tires until they reach a liftoff speed of about 62 mph (100 kph). Japanese engineers say the wheels are an advantage if a power failure caused a shutdown of the system. Germany's Transrapid train is equipped with an emergency battery power supply.
Despite U.S. interest in maglev trains over the past few decades, the expense of building a maglev transportation system has been prohibitive. Estimated costs for building a maglev train system in the United States range from $10 million to $30 million per mile. However, the development of room-temperature superconducting supermagnets could lower the costs of such a system. Room-temperature superconductors would be able to generate equally fast speeds with less energy.
For more information on magnetic levitation trains and related topics, check out the links on the next page.
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