Inductrack - American MAGLEV?

Surely most of you know something about the posssibilty to greatly increase speed and efficinecy off train transportation - use of MAGLEV trains (magnetic levitation). Such trains are hoovering above the surface so without contact with the ground their speed can be much higher than by conventional trains.



There were originally two MAGLEV solutions : German one Japannesse ones.
The German maglev uses conventional electromagnets but the system is inherently unstable because it is based on magnetic attraction rather than repulsion. Each train car must be equipped with sensors and feedback circuits to maintain the separation between the car's electromagnets and the track. THis makes the train very expensive so only one known example is built in Shanghai.

Japanesse maglev - electrodynamic system (EDS), large superconducting magnet coils mounted on the sides of the train generate high-intensity magnetic field poles. Interaction of the current between the coils and the track levitates the train. At operating speeds the magnetic levitation force balances the weight of the car at a stable position. EDS trains do not require the feedback control systems. However, the superconducting magnetic coils must be kept at temperatures of only 5 kelvins, so costly electrically powered cryogenic equipment is required. Also, passengers must be shielded from the high magnetic fields generated by the superconductors.

As you see this requirements make the MAGLEV too expensive for use. But now Lawrence Livermore scientists have recently developed a new approach to magnetically levitating high-speed trains that is fundamentally much simpler in design and operation Inductrack.

How does it work :

The new system is passive in that it uses no superconducting magnets or powered electromagnets. Instead it uses permanent room-temperature magnets, similar to the familiar bar magnet, only more powerful. On the underside of each train car is a flat, rectangular array of magnetic bars called a Halbach array. (It is named after its inventor, Klaus Halbach, a retired Lawrence Berkeley National Laboratory physicist.) The bars are arranged in a special pattern, so that the magnetic orientation of each bar is at right angles to the orientations of the adjacent bars [see top illustration on this page]. When the bars are placed in this configuration, the magnetic-field lines combine to produce a very strong field below the array. Above the array, the field lines cancel one another out.

The second critical element is the track, which is embedded with closely packed coils of insulated wire. Each coil is a closed circuit, resembling a rectangular window frame. The Inductrack, as its name suggests, produces levitating force by inducing electric currents in the track. Moving a permanent magnet near a loop of wire will cause a current to flow in the wire, as English physicist Michael Faraday discovered in 1831. When the Inductrack's train cars move forward, the magnets in the Halbach arrays induce currents in the track's coils, which in turn generate an electromagnetic field that repels the arrays. As long as the train is moving above a low critical speed of a few kilometers per hour-a bit faster than walking speed-the Halbach arrays will be levitated a few centimeters above the track's surface.

The magnetic field acts much like a compressed spring: the levitating force increases exponentially as the separation between the track and the train car decreases. This property makes the Inductrack inherently stable-it can easily adjust to an increasing load or to acceleration forces from rounding a bend in the track. Thus, the system would not require control circuits to maintain the levitation of the train cars. All the train would need is some source of drive power to accelerate it.

In the past, engineers believed permanent magnets could not be used in maglev systems, because they would yield too little levitating force relative to their weight. The Inductrack's combination of Halbach arrays and closely packed track coils, however, results in levitation forces approaching the theoretical maximum force per unit area that can be exerted by permanent magnets. Calculations show that by using high-field alloys-neodymium-iron-boron, for example-it is possible to achieve levitating forces on the order of 40 metric tons per square meter with magnet arrays that weigh as little as 800 kilograms per square meter, or one fiftieth of the weight levitated.



PERMANENT MAGNETS under an Inductrack train car are arranged in a Halbach array (above) so that the magnetic-field lines reinforce one another below the array but cancel one another out above it. When moving, the magnets induce currents in the track's circuits, which produce an electromagnetic field that repels the array, thus levitating the train car.


In a full-scale Inductrack system, the track would consist of two rows of tightly packed rectangular coils, each corresponding to one of the steel rails in a conventional track. The main levitating Halbach arrays would be placed on the underside of the train car so that they would run just above the rows of coils. Smaller Halbach arrays could be deployed alongside the rows of coils to provide lateral stability for the train car. Such a configuration would somewhat resemble its counterpart in an ordinary train-namely, a flanged wheel rolling on a steel rail. In the Inductrack the role of the "flanges" is played by the small side-mounted Halbach arrays, whereas the role of the "wheel" is fulfilled by the main levitating arrays.

Halbach arrays can also provide lateral stability if they are deployed alongside the track's circuits (below).


A primary concern for any maglev is the efficiency of the levitating system. Unlike the German and Japanese maglevs, the Inductrack requires no power to produce its magnetic field, because it uses permanent magnets. Therefore, this particular source of inefficiency is not an issue. To levitate the train car, though, currents must be induced in the track's circuits, and electrical resistance in the circuits will dissipate some of the power, converting it to heat

WORKING MODEL of the Inductrack constructed at Lawrence Livermore National Laboratory to test the system's performance. The first section of the 20-meter-long track contained electrically powered drive circuits to accelerate a 22-kilogram cart (below). Once set in motion, the Halbach arrays on the underside of the cart allowed it to coast over the 1,000 levitating coils in the second section of the track.



Costs
A preliminary feasibility study concluded that a full-scale Inductrack system would be less expensive to build and operate than the German maglev. For example, the study estimated that a train car equipped with Halbach arrays would cost between $3.2 million and $4.2 million, whereas a car in the German maglev would cost more than $6 million. (The estimated cost of a Japanese maglev car has not been made available.) The Inductrack vehicle would be more expensive than a conventional railcar, which costs between $2 million and $3 million, and building the system's track could cost as much as 80 percent more than constructing an ordinary track. The study noted, however, that the Inductrack's energy usage and maintenance costs would be significantly lower than those of a conventional railway.

Other aplications - rocket launch?
NASA awarded the laboratory a contract to build another model, aimed at demonstrating a very different application of the Inductrack concept. Studies by NASA have shown that if their rockets could be accelerated up a sloping track to speeds on the order of Mach 0.8 (950 kilometers per hour) before the rocket engines were fired up, it could substantially cut the cost of launching satellites. Such a system could reduce the required rocket fuel by 30 to 40 percent, thereby making it easier for a single-stage vehicle to boost a payload into orbit. Our Inductrack model, which will have a track about 100 meters long, will be designed to accelerate a 10-kilogram "launch cradle"-the rocket's platform-to speeds of about Mach 0.5 (600 kilometers per hour). Because of the shortness of the test track (compared with the kilometer-or-so length of a full-scale system), the electrical drive circuits for the NASA model must achieve 10-g acceleration levels. In a full-scale system the acceleration levels, limited by the strength and weight of the rocket itself, would be more modest, on the order of 3 g's.



Links

www.skytran.net...

www.llnl.gov...

www.llnl.gov...

This is a very cool and interesting find Longbow.

I think this, and the whole MagLev concept in general could really go places..er no pun intended.


I hope that this gets further funding for R&D.

America is so behind the times in our mass transit sytems. I would love to see the introduction of such trains to our large cities. Our rail system is so outdated and rather worse for the wear. Imagine what it would be like to travel across this beautiful country of ours on such a train.

[edit on 28-12-2005 by WHOFLUNGGUM]

[edit on 28-12-2005 by WHOFLUNGGUM]

Here you go, America's simpler and cheaper answer to Maglev.

Sandia National Laboratories

[edit on 30-12-2005 by NWguy83]

brain cramp

[edit on 30-12-2005 by sardion2000]

America is so behind the times in our mass transit sytems. I would love to see the introduction of such trains to our large cities. Our rail system is so outdated and rather worse for the wear. Imagine what it would be like to travel across this beautiful country of ours on such a train.

Actually the freight rail system is very up to date and a higher and higher percentage of goods are transported by rail each year. Also, there is a reason why the US mass transit is behind the times. The US is built around the automobile. Also, we have the space for people to have many automobiles.

Excellent presentation longbow and a rare Way Above from me. True visionaries seem to be becoming an endangered species in corporatopia.

I've always wondered if things like these - and I know this will sound silly - could be applied to other methods of mass transportation.

What I mean is, and this probably wont make much scientific sense - I'm an English major -, would there be a way of making an electromagnetic highway of sorts .

I wish I could clarify it somehow, but in my head it's something like a magnetized road surface with the bottom of the vehicle being of the opposite polarization. It would of course require a major balancing system so the vehicle doesnt rock away like magnets do when you force em together, but I guess what I'm asking is, from someone with scientific background - as I have none at all - would this even be possible?

I'm probably just being over-imaginative

would there be a way of making an electromagnetic highway of sorts

Some work has been going into creating a hy-brid car that can hook up to an electromagnetic rail for handsfree convoy travelling. Sort of like a monorail except when you get to your destination you drive off the track and start travelling normally. There are many issues with this one of the biggest being infrastructure and the lack of these types of cars.

Originally posted by longbow
A preliminary feasibility study concluded that a full-scale Inductrack system would be less expensive to build and operate than the German maglev. For example, the study estimated that a train car equipped with Halbach arrays would cost between $3.2 million and $4.2 million, whereas a car in the German maglev would cost more than $6 million. (The estimated cost of a Japanese maglev car has not been made available.) The Inductrack vehicle would be more expensive than a conventional railcar, which costs between $2 million and $3 million, and building the system's track could cost as much as 80 percent more than constructing an ordinary track.

Comparing the costs of a car is bull# if you know one km of track costs 10.000.000 euro or 12.500.000 dollar for the French TGV. You need to compare the cost of the track between the Inductrack and the Japanese and German maglevs. Figures are a bit hard to find, but 80% more than the French ordinary track would mean around 20.000.000 dollar per km. I don't know how much the German maglev system is, but the Chinese think by modular construction and so on they can get it down to 18.000.000 dollar per km.

Originally posted by longbow
The study noted, however, that the Inductrack's energy usage and maintenance costs would be significantly lower than those of a conventional railway.

So does the German and Japanese maglev.

A real comparison is lacking and not possible since noone has built an Inductrack system yet while Maglev systems DO exist.