Flying Trains

leb writes: "Engineers in Japan are developing trains that really do fly. Using the 'wing-in-ground' (WIG) effect, in which a high-pressure cushion of air forms underneath flying objects as they approach the ground, they believe they will be able to create trains that use only a quarter of the power required for magnetically levitated (maglev) trains. Read about it in this New Scientist article." This is rather nifty, but it isn't as cool as the flying train at the end of BTTF III. Put a flux capacitor on this baby, and we'll talk.

Comments

Inductrack

[maggard]

Lawrence Livermore's "Inductrack" seems much more feasible then winged trains. It fits onto current right-of-ways, no exotic technologies are required (no super magnets, etc.), and is quieter then existing vehicles. It's rails can be made of low-cost materials and the levitation system is conventional magnets in arrays. The levitation effect comes into play at speeds over 5 kph and improves up to 500 kph so a train simply rolls up to speed (a fast walk) and then glides from there. Best yet it's a passive effect inherent in the design - power failures don't cause the train to suddenly drop onto the rails (a problem with the Japanese and German designs.)

See:

"Inductrack"

Maglev: A New Approach, Scientific American (January 2000) - article not available online.

"Track to the Future," Popular Mechanics (May 1998), pp. 68-70.

Wing in Ground?

[KlomDark]

Who made up this "WIG" term? As long as I can remember, this has always been referred to as "Ground Effect".

Essentially, this means that a wing, such as one on an airplane, gets double lift when the wing is as close, or closer, to the ground (vertically) as the wing is wide (horizontally). In other words, if a wing is 75 feet wide, and the plane is 75 feet or less from the ground, the wing will be able to generate twice the normal (above 75 feet) lifting force.

This can create a lethal effect on overloaded or badly balanced (front to back) aircraft: The wings will generate double-lifting force while within the ground-effect zone, but as soon as the plane gets above the ground effect layer, the plane will flip over backwards and splatter all of the runway. Not a fun way to die. Always do those Weight-And-Balance calculations carefully!

One time I was on a puddle-jumper (20 seater deal prop) going from Omaha to Minneapolis. We had gotten on the plane and were waiting to begin taxiing to the run way. The door was closed. Suddenly, they open it back on and let this digustingly fat man on the plane. He must have been 500 pounds or more. The only place he could sit was on a bench all the way at the back of the plane. (The back of the plane is the worst place for weight in the first place, the tailwing doesn't create a whole lot of lift) Since he was on so late, I doubt he made it into the W&B calcs. I love to fly, but this time I about got up and got off the plane. I stayed on and was pretty scared while we passed through the ground effect zone. There has to be a significant chance (at least 10%) that we could have flipped over. One person could have moved the wrong way, or something in the luggage compartment could have shifted and we would have been a textbook case of why obsessive-compulsive people should be kept away from both McDonalds and small airplanes! :)

Yawn. Old hat.

[Pig Hogger]

Yawn... Old hat. Can't you slashdotters have a look at history? Otherwise, you'll be condemned at repeating it... badly.

First, a brief word about ekranoplanes (a.k.a. Wing-In-Ground effect). Here is an actual picture of such a beast in flight (Gerry Anderson fans will be delighted by this one). They have been around for almost 40 years, having been devellopped in the defunct Soviet Union . You may look at this page for historic information, as well as pictures of enormous ekranoplanes as well as the 400 ton Lun ICBM launcher . For those who worry about greenhouse gas emissions, there is also a pedal-powered WIG !!! Oh, yes, those craft are already covered by a Canadian regulation, proof that they've been around long enough to rouse the attention of regulators...

Now, about trains. Nothing really new, there either.

In the 1960's, french engineer Jean Bertin (1917-1975) pursued the développement of his ill-fated Aérotrain , which, 30 years before the recently-canned german Transrapid maglev, almost reached the realization stage (both in a commuter rail line betwen Paris and the western sububurb of Cergy, and a line between Lyon and Grenoble for the 1968 winter Olympic games). Bertin's Aérotrains ran on a single inverted T concrete rail, and used a cushion of air for sustentation. An early prototype, the Aérotrain expérimental 02 (which looks like it was inspired by this), reached the speed of 400 km/h in 1966 and 422 km/h in 1969 (not an impressive achievement, since at that time, the rail speed record was achieved in 1955, when an ordinary locomotive pulling four totally normal cars reached the speed of 331 km/h on a perfectly standard railroad line). More pictures are available here.

Despite that, Jean Bertin built more prototypes, and a 20 km long rail line (which still runs accross the countryside, completely abandoned) on which a much bigger "train", which ran not much faster than today's TGVs do (note that the record certificate is issued by the Fédération Aéronautique Internationale , and not the Union Internationale des Chemins de Fer ...).

Bertin's Aérotrain technology almost got selected in place of the current TGV, but at the last minute, State support was withdrawn from the Société Bertin. The Aérotrain (and any other newfangled guided transportation system such as maglevs and monorails - we're in the real world, here, not in Disneyland) suffered most from gross incompatibility with existing rail lines (necessary to enter the core of cities) and an extremely heavy implementation of switches, which precludes their widespread use and thus reduces the flexibility of their rail networks.

Jean Bertin never recovered from the shock of losing State support; he died a few months later, despite having built a prosperous engineering company which still thrives in high-technologies.

Throughout the Aérotrain's history, the French National Railroads (SNCF)'s attitude was extremely interesting. Despite all the media hoopla that surrounded the Aérotrain and the political interest, it did not say anything at all. Not a single word either for or against the Aérotrain was uttered in official french railroad circles. But during that time, the SNCF worked hard at perfecting what is seen today as the epitome of high-speed travel technology, the TGV.

So, it is quite safe to say that this oldfangled flying "train" will certainly not fly very far, because the theorical speed limit of ground travel, the speed of sound, is within reach of conventionnal steel-wheel-on-steel-rail technology, which without much pain, ran at 515,3 km/h on May 18th 1990 (gee! Almost 10 years ago!!!).

(What is the speed of sound at 20C at sea level anyway???)

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Fix for broken link

[joshamania]

Here is the fix for that broken link.

Re:Dimensions?

[costas]

Alright... let me start debunking:

(a) the ground effect is a very well understood phenonomenon, much more so than MAGLEV. In fact, the Russians/Ukrainians have built massive WIG aircraft, that were probably gonna be used for rapid troop landings. A quick Google finds this page.

(b) WIG has nothing to do with turbulence. In effect when a wing is closer to the ground, the space between the underside of the wing and the ground acts as a nozzle, i.e. increases air pressure much more so than the wing can do by itself (roughly 2x). Increased air pressure => higher lift (although I am over simplifying here).

(c) You don't have to have a large wingspan to take advantage of the ground effect. It just so happens, that when you fly slow, you can't produce as much difference in air pressure with a small wing, so you need a large one (again, I am over simplifying, but close enough). I.e. if you have lots of small wings, like these Japanese are trying to do, you're gonna get pretty much the same effect.

(d) The pterodactyles did not use the WIG effect... I mean come on, do you ever see illustrations of pterodactyles soaring at 2' off the ground? ;-)...

I personally think this is a very interesting idea. Maglev is cool and all, but this can work just as well. If I had to find a weak spot it would be the total cost of ownership (TCO) of these things versus a Maglev train... with a maglev, electromagnets may cost more at installation, but after that you're pretty much done spending. OTOH, aircraft (particulary aircraft *engines*) are notoriously expensive to maintain...


engineers never lie; we just approximate the truth.

nature of innovation

[konstant]

The W.I.G effect has been understood for a long time; this is a clever application of that effect across disciplines.

This proves an interesting reminder of the fact that "innovation" - an overused term - is so much more than the ability to spawn new ideas fully formed from your brain. Some of the most brilliant advances we have seen and will see are the fortuitous combination of two seemingly unrelated facts or areas of study. That's real genius: the ability to see patterns where a less perceptive person might see none.

I hope someone points to initiatives like this one the next time funding for pure science research is on the block. The quest for knowledge is almost never totally without payoffs.

-konstant
Yes! We are all individuals! I'm not!