What happens when a maglev train loses power?

[Satisfying Andy Licious]

As I understand magnetic levetation (maglev) trains, they float above the tracks. So what happens if they lose power? And I don't as in mean "does a backup generator comes on?" I mean every source of power fails -- what happens to a formerly floating train traveling at high speed? Does it have emergency wheels? Does the train do a belly landing and scream across the tracks until it stops?

Surely something like this must have happened by now.

[scr4]

From the FAQ on the Transrapid (http://www.transrapid.de/en/index.html) site:
Question: What happens when the power fails?
Answer: When the power from the mains fails during driving, the levitation and guidance system is supplied by means of onboard batteries which are charged without contact during driving. Therefore, the vehicle will use its existing "momentum" to glide to the next stopping area. Should the next stopping area be too far away, the vehicle stops at one of the auxiliary stopping areas provided for the purpose at regulation intervals along the guideway. The vehicle is stopped with the aid of a non-contact eddy current brake which is also supplied from the onboard batteries and brakes the vehicle to a speed of 10 km/h. The vehicle is then lowered onto skids and stops after a few meters. An emergency stop on the open track can be ruled out.

It doesn't mention what happens in the case of a catastrophic failure of the levitation system. I guess there are enough redundant systems so that a complete failure is unlikely.

[TheLoadedDog]

This is a reason the Japanese claim their system is superior as it uses wheels to get up to "take off" speed, and these wheels cvan be used in a a power failure.

[Sublight]

I read about a particular arrangement (Holbach array?) in Scientific American that lets you build a one-way maglev track out of permanent magnets, rather than requiring electromagnets. Aside from being a lot cheaper to run (though maybe more expensive to build), it eliminates the power loss problem, since the train remains floating as it coasts to a stop.

[scr4]

Originally posted by TheLoadedDog
This is a reason the Japanese claim their system is superior as it uses wheels to get up to "take off" speed, and these wheels cvan be used in a a power failure.
Maybe, but that's only because their system can't levitate at low speeds. IIRC the levitation coils are embedded in the track, and current is induced as the electromagnets on the vehicle move over the coils.

The Japanese system levitates much higher than the Transrapid. I've also heard this claimed as an advantage (more margin for error in alignment, I suppose). On the other hand, the Japanese system is expensive (this page (http://www.monorails.org/tMspages/TPMagIntro.html) claims $148 million/mile construction cost), and has all the problems associated with the use of cryogenic superconducting magnets.

[Satisfying Andy Licious]

Originally posted by scr4
From the FAQ on the Transrapid (http://www.transrapid.de/en/index.html) site:


It doesn't mention what happens in the case of a catastrophic failure of the levitation system. I guess there are enough redundant systems so that a complete failure is unlikely.
Maybe I'm too much of a Murphy's Law type, but if you run an operation often enough, eventually there will come a time when each system malfunctions at the same time. Do they have any plan for losing all power at high speeds? Even saying they've got some kind of skid pads would make me feel a little more confident.

I once took a ride on the historic "Angel's Flight" mini-rail in Los Angeles, and a few months later it snapped and killed someone, even though such an accident wasn't supposed to happen.

[Shalmanese]

I'm sure an airplane probably has about the same level of redundancy. Sure, occasionaly a plane will fall out of teh sky when every single fail-safe fails. But its still an acceptable risk.

[Broomstick]

Major difference with airplanes, though, is that they can keep flying even without power - google "gimli glider" or even search "gimli glider" here on these boards - and can "coast" to a landing (it's called "gliding"). What does a maglev do? Crash to the rail?

[scr4]

Originally posted by Sublight
I read about a particular arrangement (Holbach array?) in Scientific American that lets you build a one-way maglev track out of permanent magnets...
Sounds like the "Inductrak" system developed at LLNL. Here's some info:
http://www.llnl.gov/str/Post.html
http://www.llnl.gov/str/November03/Post.html

[Hari Seldon]

Originally posted by Sublight
I read about a particular arrangement (Holbach array?) in Scientific American that lets you build a one-way maglev track out of permanent magnets, rather than requiring electromagnets. Aside from being a lot cheaper to run (though maybe more expensive to build), it eliminates the power loss problem, since the train remains floating as it coasts to a stop.

If it was the article I read, it was probably about 30 years ago and the plan was to run in an enclosed partially evacuated tunnel supported by permanent magnets. The train would accelerate through gravity and air pressure from behind. It sounded like a pie in the sky (or underground, rather) idea and I have never heard of it since.

If I were designing a maglev system, I would put in wheels strong enough for emergency use, although not long term use. The Montreal rubber-tired Metro rides on wooden boards, but there are emergency tracks and every car is fitted with standard rail wheels for emergencies. I have not heard of a failure that resulted in the track being used, but that doesn't mean it has never happened. A long time ago there was an accident involving a tire that went flat and heated up and caught on fire. A car was destroyed and, IIRC, there were some deaths from smoke inhalation.