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Can magnetically levitating trains run at 3,000km/h?

Trains that use magnets to levitate above the tracks might sound like something from Back to the Future, but the concept of magnetic levitation has been around for many years. Maglev trains, which use…

Faster than a plane? Alex Needham, CC BY

Trains that use magnets to levitate above the tracks might sound like something from Back to the Future, but the concept of magnetic levitation has been around for many years. Maglev trains, which use this technology, were first developed in the 1960s and many different methods have since been developed to free trains from their earthbound wheels, axles and bearings.

Maglev trains sidestep two of the limitations conventional trains have. First, because a wheel typically weighs around a tonne, the wheel pummels away at the rail at high speed, needing regular maintenance to keep the track up to scratch.

Second, trains drive and brake themselves via this mechanical contact and therefore must carry propulsion equipment on board. This is fine at speeds of up to 400km/h (the speed of proposed Britain’s HS2 line), but aerodynamics makes going much faster very difficult. A lot more power is needed for small increase in vehicle speed. For example, operating at 400km/h instead of 300km/h needs nearly two and half times as much propulsion power, so at very high speeds the propulsion needed becomes impractical.

A 19-mile journey in just a few minutes, all in first-person

Maglev’s ‘magic’

All Maglev technologies use some form of magnet – this could be a permanent magnet, an electro-magnet or a magnet using a superconducting coil. The train floats atop this magnetic field and is given support and guidance from the interaction that takes place between the magnet and another element on the ground, such as a steel track, a conducting element in the track or another magnet. Elimination of direct mechanical contact they can reach higher speeds.

Despite the variety of Maglev concepts that are possible, there are two common types. The first is known as the Electro-Magnetic System (EMS), and has an electro-magnet providing the force of attraction to a steel rail. The second is known as the Electro Dynamic System (EDS) which uses a powerful magnet. This interacts with a coil or sheet of aluminium in the track formation. When the magnet moves along the track a force of repulsion is generated, and the vehicle rises a few centimetres above the track, but only when moving at a considerable speed so wheels are still required at low speeds.

Of course driving and braking Maglev vehicles is still necessary – this is also achieved through magnetic effects. To achieve high-speed operation, coils are fitted to the track and these are used to create a travelling magnetic field which essentially drags the vehicles along by their magnets. Therefore it is no longer necessary to carry the heavy power equipment on the trains: instead the equipment is fitted to the track, making the trains lighter and able to travel significantly faster.

The Shanghai EMS Maglev Train operates regularly at 430 km/h, and in Japan JR Central’s prototype EDS Maglev system can run at more than 500 km/h. There are Maglev technologies that can push speeds up to around 600 km/h.

The sleek MLX01 is one of Japan’s latest Maglev designs. Takashi H, CC BY-NC-SA

Interestingly, in the 1960s there was a general belief that 200-250km/h was the limit for conventional trains, but now we have regular service at over 300km/h, and 400km/h is entirely feasible. The mechanical contact between the wheels and the track remains, but it is also possible for the Maglev-style propulsion system to be used for normal trains, even though they don’t have the magnets.

Costly reality

The reality of getting trains up to speeds over 1000km/h is not as simple as the theory. Even Maglev trains have to contend with aerodynamics. This is why the higher speeds that have been postulated by the American entrepreneur Elon Musk in his concept Hyperloop (1500km/h) and the Chinese “Super Maglev” (2,900km/h) propose running in a partially evacuated tube to reduce the forces going against them. Such high speeds therefore depend upon the ability to construct and maintain a very accurately aligned guideway, within a low pressure tube over hundreds of kilometres. This is where it becomes really difficult, and very costly.

And yet some of these high-tech propositions make bold claims about cost. In reality transportation providers would be enormously excited by the prospect of reducing the system costs by 30% or 50%, but often the proponents of new concepts suggest much larger savings. For example, Musk suggests a 90% reduction in cost compared with a high-speed rail system, despite the sophisticated infrastructure that would be required. Unfortunately this takes the idea from being exciting to being unbelievable and may well be a case of Back to the Future.


Update: This article was corrected to reflect that air resistance at higher speeds has greater impact than mechanical contact between the rails and the track. The text was modified to remove the incorrect term “exponentially” when explaining how much extra power is needed for increasing speed.

Next, read this: Is Hyperloop the future of ground transport?

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10 Comments sorted by

  1. Laurence Blow

    President, MaglevTransport, Inc.

    Nice summary-level article covering many points about maglev systems, and thankfully free of the technical blunders more commonly found in general-media pieces.

    Two small quibbles: First, including the image of the Japanese high-speed maglev MLX01 is fine, since it was the workhorse testing vehicle at the Yamanashi test track, but the latest pre-production vehicle, the L0 Chuo Shinkansen maglev, is a much different aerodynamic design and its image would have been a bit more timely.

    Second, at the risk of being called a pessimist, it seems to me that attaining 400km/h speeds for conventional steel-wheel trains is straining the technology past the breaking point. Only the most linear and level alignments could allow it and, more practically speaking, the maintenance costs would be crushing. Is anyone actively considering such a thing?

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    1. Roger Goodall

      Professor of Control Systems Engineering at Loughborough University

      In reply to Laurence Blow

      Thanks for your positive comments about the technical correctness!

      Regarding conventional steel-wheel trains, 400 km/h is seen as both operationally and economically feasible. For example the route alignment for the UK's High Speed 2 railway has this as its design speed, although it won't run this fast initially.

      By the way, the photo to illustrate the Japanese high-speed system was chosen by the The Conversation's editors!

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  2. John Harding

    FRA Maglev Chief Scientist (retired)

    "Maglev trains sidestep two of the limitations conventional trains have. First, the mechanical contact that conventional trains have between their wheels and the rails slows them down."

    This first issue is a common error regarding rail vs maglev. Actually the force to overcome wheel rail resistance is lower for modern high speed rail than levitation drag at low speeds. At high speed aero drag predominates and rail resistance is negligible by comparison. See my post at the International Maglev Forum for details.
    http://magnetbahnforum.de/phpBB2/viewtopic.php?p=49394#49394

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    1. Roger Goodall

      Professor of Control Systems Engineering at Loughborough University

      In reply to John Harding

      Thank you for this clarification, which I completely agree with. In fact the sentence to which you refer has been changed by the editors. What I wrote was "Firstly there is the mechanical contact between the wheels and the rails, and because a wheel typically weighs around 1 tonne, at high speed the wheel pummels away at the rail requiring continual maintenance to keep the track up to scratch."

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  3. Rich Rich

    logged in via Facebook

    Amazing. I fully support HS2 to but not the technology. This is what we need. It will be interesting if the SwissRapide project goes ahead.

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  4. Jose Claret

    Mechanical Engineer

    Hello, I just found your article on ifls.com and as a Mechanical Engineering student I wanted to point out some things that were unclear to me.

    There's a statement in the beginning:
    "The amount of power needed increases exponentially in proportion to the vehicle speed"
    That's not really true, as the amount of force the vehicle has to exert to overcome air resistance varies quadratically with velocity and the propulsion power varies CUBICALLY (NOT exponentially). This is so, as air friction is modeled…

    Read more
    1. Roger Goodall

      Professor of Control Systems Engineering at Loughborough University

      In reply to Jose Claret

      Thanks Jose, your analysis is of course correct. Unfortunately the editors of The Conversation decided to make a change for the published version, because I had written "The amount of power that's needed for it increases in proportion to the vehicle speed cubed." I guess they felt that calling it an exponential increase would mean more to the average reader!

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    2. In reply to Jose Claret

      Comment removed by moderator.

    3. In reply to Jose Claret

      Comment removed by moderator.

  5. Jonathan Clark

    logged in via Facebook

    Glad to find a spot to mention this that I feel like will recognise it... threads of hundreds of comments get lost quickfast and in a hurry...

    Everyone talks about these ultra high speeds in terms of the creation of a vacuum, and of the cost and difficulty that presents... but - what about instead simply Moving the Air Within the tube at an increased speed?!
    If you put, say, a large jet engine at the end of the tube and sucked air through its system like a reverse wind tunnel, then the train's…

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