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String Rail - a low cost, low impact, high speed transport alternative

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June 3, 2010

Artists rendering a String Transport system

Artists rendering a String Transport system

Image Gallery (5 images)

Trains might be a reasonably cheap transport option - but rail infrastructure is very costly to build. Monorail, maglev systems and high speed rail are more expensive again - and prices really skyrocket when you have to build bridges, tunnels and winding mountain routes, or cover difficult terrain. Which is why Anatoly Unitsky's String Transport Systems look like they've got so much potential. The system uses solid steel/concrete rails, reinforced with extremely high tension steel wires, to provide an efficient and smooth rail system anywhere between 3 to 30 meters above the ground. It's earthquake, hurricane and terrorist-proof, and capable of supporting vehicle speeds over 500 kmh, too, making it a genuine high-speed rail alternative, for a fraction of the price of road or ground rail alternatives. Fascinating stuff!

The String Rail System

The UST uses steel or concrete rails, reinforced by hundreds of high-tension wires running through the middle of the rail, suspended above the ground on towers approximately 30 m apart. Unlike roads or rail systems, it can traverse mountains and other rough terrain in a straight line, and it's equally adept at crossing shallow waters, desert or forest, with minimal environmental impact at the ground level.

Optimal height for a UTS support tower would be around 5-6 m above ground - or 10-20 m where the underlying terrain is very rough. If money is no object, there's no reason why support towers couldn't be increased to as much as 100 m high or more.

Because it's a combination of solid steel/concrete and high-tension wires, it's not really appropriate to think of the UST as something like a chairlift. In fact, it's more accurate to look at a UST track more or less as a tiny pre-stressed concrete bridge, built for a fraction of the cost of a ground rail system or even a motorway.

A fraction the cost of rail

The above video outlines the rough process of building a UTS installation, and also shows a modified truck driving on an early demonstration installation in Russia.

A UST system is cheap to install for the simple fact that you can built it with a minimum of materials per km, and a minimum of ground preparation. You don't need to build expensive overpasses, tunnels or other infrastructure to make the UTS fit in around existing roads and other infrastructure - it's already up off the ground and out of the way.

Cost estimates are so low as to look downright suspicious - Unitsky quotes a figure of as low as US$50,000 per km for assembled string rail. Compare this to the cost of recent low-speed surface rail installations in Australia - from which the cost of a double-track rail service, not including land acquisition or station building, is very optimistically estimated at around AUD4.12 million (US$345 million) per km. The real cost of underground rail is in the realm of 10 times higher.

Unitsky estimates the final cost of a high-speed UST installation as being somewhere between three and 10 times less expensive per km than a railway, maglev system, monorail system or motorway. This is borne out in the estimated project cost of a potential installation between Abu Dhabi/Dubai/Sharjah - a 138km route estimated at US$280 million, or a little over US$2 million per km. It's unclear where this figure comes from, or whether it includes land acquisition, stations and other supporting infrastructure.

350-500kmh high speed string rail

The running surface it provides is exceptionally smooth - the tension of the steel wires within each rail ensures that there's a sag of only 1-5 cm between support posts so there's no perceivable 'bump' as a vehicle passes over them.

The smooth surface and negligible sag make the UST appropriate for high speed transit - Unitsky believes 350 kmh (~220 mph) should be immediately within reach, with 500 kmh (over 300 mph) possible after further development.

Aerodynamics are on the UST system's side as well - the biggest issue for ground vehicles at high speed is the pressure generated by air passing underneath, which causes the vehicle to lift off the ground. Formula one cars and other high-speed ground vehicles combat this by using spoliers and other design features to catch wind on the top of the vehicle and push it downward.

A UST system has no need for these kinds of aerodynamic inefficiencies - the vehicles can be shaped for minimum frontal drag with no consideration for downforce, as air underneath the vehicle can move as freely as air above it.

The aerodynamic drag coefficient of the Toyota Prius, a leader in passenger car aerodynamics, is around 0.26. A hummer H2, built with almost no drag consideration, has a drag coefficient of around 0.57. The German-designed Transrapid Maglev monorail connecting Shanghai to the Pudong International Airport has a top speed of 430 kmh and a drag coefficient of 0.26 - and a passenger vehicle designed for the string transport system has already been wind tunnel tested as having a drag coefficient of just 0.075. This is a big deal - as speeds increase, aerodynamic drag becomes far and away the biggest force a moving vehicle needs to overcome. The UST has a big advantage here.

Aerodynamic efficiency, coupled with the rolling efficiency of steel or alloy wheels on a solid concrete beam, lets the UST reach high speeds without requiring huge amounts of power. A simple 80 kW (107hp) engine is all you'd need to get a 20-person passenger vehicle up to 200-250 kmh. With a 200 kW engine, you could hit 400 kmh - a feat that the Bugatti Veyron needs over 700 kW to achieve.

A few string rail tidbits

There's so much information at the String Transport website that we could sit here writing about this system all week - so, while the high speed, high efficiency and low rollout cost of the UST system are probably the key features, here's a few other interesting tidbits:

  • Anatoly Unitsky first started developing the UST system in 1977, and between him and a team that has at times included as many as 100 people, total development time stands at more than 500 man-years;
  • A pilot installation in Khabarovsk, Eastern Russia, was planned for 2008, but canceled after specialists from the Moscow State University of Railway Engineering gave the project a negative review;
  • For the most part, vehicles will travel more or less horizontally on the UST string rails. But if a load needs to be carried up a steep gradient, it's possible to use a different wheel configuration that increases friction and enables travel at up to 45-60 degrees of elevation;
  • Unitsky claims the combination of rigidity and high tension makes the UST track structure extremely resistant to wind deflection - even hurricane-strength winds that can destroy power lines should have little effect on the UST structure. I'm not sure I'd want to be riding a string rail vehicle in a hurricane myself, though!
  • Unitsky appears to be currently living in New South Wales, Australia, where his new company String Transport Systems is trying to get the UST system off the ground (pun intended) as a mineral haulage alternative in the Australian mining industry, where difficult terrain often inhibits mining operations;
  • Due to the high tensions involved, it's not a simple operation for a UST track to go around a corner. Gentle curves are OK, but if you need to make a 90-degree turn, for example, you need to build a section of solid, non-tensioned rail for this purpose, and let the tensioned UST system lead in and out of the corner;
  • If some catastrophic event, like an earthquake or a terrorist attack, was to destroy one of the support towers, passengers on the UST would hardly notice, according to Unitsky. The doubling of bridge span would result in an increased track deformation, but this would be taken up by the vehicle's suspension.

Here's another video - a CAD mockup showing how Unitsky envisions the UST operating as an urban and regional transport system. Let us know if you can translate the Russian for us!

The next video covers a range of the technologies Unitsky has patented in the 33 years he's been working on the system - including some pretty nifty vehicle designs and prototypes.

And finally, another video showing the rather sorry recent state of the original UST test installation from the first video. Situated in Ozery, around 100km outside Moscow, the test rig (built around 2001? ... the date is hard to pin down) now sits unattended, and as the videomaker points out, you can wander in and out and climb around on the facility as you please.

This video also offers a great close-up view of the UST technology, years after its original implementation. It looks a little rusted, warped in places and in a general state of disrepair. I wonder if that warping is any cause for concern!

Where to from here?

In all, the Unitsky String Transport System is a fascinating transportation alternative that seems to have notable advantages over rail, monorail, maglev and road transport.

Would I find it a bit freaky to be doing 350 kmh while hanging from a wire? Yes sir. Am I entirely convinced that the strings won't snap, even if a tower or three get taken out? No. Would a full scale demonstration convince me? Probably, yes. And this is the stage Unitsky is stuck at. His demonstration rig is small-scale, and there's nothing like the UST in operation anywhere in the world.

He's just finished a round of fundraising in Australia, and is currently planning to build a larger scale pilot/demonstration track. To be of satisfactory value as a demo rig, the track will have to be at least 2km long - which would then need to be extended to around 8km if high-speed testing was necessary. To get this far (stage 2 of the UST pilot implementation plan) will cost around US$15 million, and take 2.5-3 years.

We wish Unitsky all the best and hope to hear good results as the test rig and possible commercial installations come to light.

For more information, visit the American STU website.

About the Author
Loz Blain Loz has been one of Gizmag's most versatile contributors since 2007. Joining the team as a motorcycle specialist, he has since covered everything from medical and military technology to aeronautics, music gear and historical artefacts. Since 2010 he's branched out into photography, video and audio production, and he remains the only Gizmag contributor willing to put his name to a sex toy review. A singer by night, he's often on the road with his a cappella band Suade.   All articles by Loz Blain
21 Comments

I'm interested. If 50% of the claims made are true it would be a major leap in mass transit. Imagine this tech used as the main transit service connecting near cities. I think that Vegas would be an appropriate site where a full scale version could be tested. Flat, open, with a straight run from the airport to the strip. Plus people who are willing to take risks are in no short supply, lol. (BTW. I must say that I'm not sure where the "terrorist proof"ing of this system exists as claimed in the first section of the article.)

TheSaleem
3rd June, 2010 @ 08:48 am PDT

They should build this in Perth, when they build the line to the airport.

David Anderton
4th June, 2010 @ 12:05 am PDT

This rail system has been tried previously, albeit in a slightly different way. The overhead cable bus in the city of Mannheim, Germany, ran on track ropes like a cable car and was supposed to be a rapid transport system. Unfortunately, the dynamics of the system were not foreseen and the system was not a success. During use at higher speeds the rope in front of the vehicle formed a wave that could not pass the next support, resulting in a nasty vibration on the constantly shortening remaining segment of rope between the car and the support. This system seems better in that it is stabilised a bit more, but there still may be complications due to the light weight of the 'rails'. I wish the designers good luck with this though, maybe they can come up with a suitable dampening system.

Rolf
4th June, 2010 @ 01:44 am PDT

This is very similar to the Northrop-Grumman TTWIG, (Track Tethered Wing in ground effect).

In their concept the rail only provides guidanc and support while at rest.

In flight, the TTWIG has "wings" that generate lift, and flight is limited to ground effect only via a tether. (GROUND EFFECT LIFT IS 2X NORMAL) Propulsion was first envisioned to be either jet, or prop, but later electric driven prop was the final answer. It was envisioned to take advantage of the center poartion of the US Interstate Highway system.

Each "station" was to have a compressed air or steam catapult system to get the TTWIG up and running almost instantly.

The company abandoned the concept.

Phil.Poulos
4th June, 2010 @ 07:14 am PDT

This shows the potential of innovation for a better greener world of mass rapid transport.

Leong Hee Chan
4th June, 2010 @ 07:24 am PDT

The sinusoidal wave-form harmonics created by an object travelling along a 'string' are what will limit its speed, this is basically a high-speed cable-car. Not gonna happen. A better way is to suspend tube sections by cable underneath inverted L-shaped pillars through which a vehicle could travel - it works for fluid pipelines, it could work for a high-wire subway too.

PeetEngineer
4th June, 2010 @ 07:56 am PDT

This is a fantastic idea, but the concept can include other services that have not been mentioned.

1. Why can't the system allow privately owned automated vehicles (such as sedans, recreational vehicles, and cargo transporters) thus replacing our expensive to install and maintain interstate road and expressway system. With the string rail system terminating in our neighborhoods, commuters could "mount" the system close to home and have a safe, automated method of transportation to their desired destination.

2. Commuters could safely use communications devices (cell phones, computers, etc.) without endangering other drivers while traveling from point A to B.

3. A company could send automated, driver-less cargo carriers from distribution centers to neighborhood outlets (think grocery stores).

4. With the addition of superconducting technology, the system could become the true "Super Grid" for electrical power distribution the world over.

5. Why can't our fiber optic telecommunications be integrated within the string rails to lower the cost of fiber distribution.

6. Fifty thousand automobile deaths per year -- Eliminated. Millions of deaths per year world wide -- Eliminated.

7. No more riding disease spreading buses and mass transit vehicles.

8. Elevating the system gives the ground level back to humans and animals (no more deer / car collisions).

There are hundreds more reasons that this system is the way to go.

Peachtree City Mike
4th June, 2010 @ 01:10 pm PDT

THis is good news, even better that it becomes a maglev superhighway with the addition of a copper plate on the tubular steel, and the good news is that they (the sections)do not have to be connected to each other so expansion and contraction problems gone... Why hasn't anyone else seen this? Moving magnets levetate above copper and can generate field. So the cost becomes what 5280 x 2 pounds 1560lbs times $3 per lb equals 4680 so for 55000 per mile we have mag lev with very high speed possibilities.

When can we build??

Frostedpanda
4th June, 2010 @ 01:28 pm PDT

@Phil.Poulos,

That TTWIG sounds very interesting. I daydreamed an almost identical concept some years back. Why did they abandon it? There's no information on it on the Web at all.

Gadgeteer
4th June, 2010 @ 04:12 pm PDT

This is novel and is an option for different application of rail systems (including non-mass rapid transport). Reminds me of a roller coaster in an amusement park though! And can this be adapted for maglev? It certainly looks more cost/resource effective.

TC Lai
4th June, 2010 @ 04:28 pm PDT

"It's earthquake, hurricane and terrorist-proof" Get real is all I can say.

foghorn
4th June, 2010 @ 09:34 pm PDT

Well, I don't know. Maybe I am too skeptical. It would be so easy to terrorise - would not need much thought. How can you claim high speed capability, if you have a converted army truck climbing the track as a trial. 500km/h? No way!

What about oscillating tracks, vibration, and how can it be cheap going across long distances with pylons 10 metres apart? However, the idea if great, innovation is what we need. There have been top or bottom monorails for over a hundred years. What is so different? How are you going to propel the 'trains'? Conventionally? Please prove me wrong!

Facebook User
5th June, 2010 @ 10:39 pm PDT

Another poster has already commented on the resemblance to the Aerobus system built for Mannheim. The basic principle is sound in both cases - carry the main structural loads in tension instead of compression and bending. The more you can do this, the cheaper and lighter the structure can be. The problem with the Aerobus system is that there was no preload; it needs to be altered so that the rails are supported by a two-way cable truss to increase the effective stiffness of the rail and thus allow higher speeds. This principle of preload IS incorporated into the String Rail system, which gives it that much smaller sag (still too much for the specified speeds, though) and a much simpler support system, but the very small depth of the cable curves required by burying them inside the beam will limit the distance between support pylons, which are the big drivers of the cost per kilometer. I would envision a hybrid system - String Rail in built-up areas where frequent changes of direction and station stops are going to require closer support spacing anyway, and Aerobus for intercity runs where the external cable truss allows wider spacing of the support pylons. Good stuff!

piolenc
6th June, 2010 @ 03:33 am PDT

The general idea of suspending wire tensioned tracks, rail, or whatever over the ground is very good one for decreasing cost by greatly reducing the amount of ground prep (grading) and material in the track itself, but there are many technical dealbreakers as have been mentioned in previous posts. A modified lower speed system may work. First, throw 500kph dreams out for now. I would hang the cars from the rails for more stability and self aligning, plus it will redice and simplify the loads between car & track, and you can possibly go with a single rail (or tube). Then lengthen cars or link them together for stability even at around 100mph(161kph). Still some technical things to overcome, but starting with a slower hanging urban system would prove it out and get real world experience to build on.

Mark in MI
8th June, 2010 @ 10:41 am PDT

Why do the mock-ups of these things always have two rails? It seems to be a car running on two really, really narrow bridges. I don't think I'd ride on that for fear of it falling off on the corners.

Why not a triangular-shaped car with the wheels recessed into the points running on three strings? You could then twist the car around corners (there will always be corners) at speed with no risk of falling off or losing traction.

Plenty of photos of the Soviet truck-based example at English Russia

http://englishrussia.com/index.php/2009/06/29/the-story-of-the-string-train/

Facebook User
8th June, 2010 @ 07:21 pm PDT

I'm surprised that Gizmag would publish this technology but not PRTs, Personal Rapid Transit? PRTs appear to be a much more viable and tested system that could sustain some of the harshest environmental conditions. There is one already built at Heathrow Airport in London and there are many others being considered around the world. Vectus is another that has already been tested and is ready to go which also doesn't use batteries.

anastas
12th June, 2010 @ 12:12 am PDT

First build a large scale model, work out the kinks, and then reveal it to the world. It's a great idea but many demonstrations are going to be required due to people's concerns. An efficient turning mechanism will definitely be needed as well.

Facebook User
23rd June, 2010 @ 08:09 pm PDT

One little question... how do you build a corner?

All the vids seem to show straight tracks...

Eric Hustedt
24th June, 2010 @ 11:55 am PDT

The company has its website: http://stringtransport.com

You can find the answers for your questions in their FAQ-list: http://stringtransport.com/?page_id=449

The project has a long history and most of the technical problems are already resolved.

Synapse
12th July, 2010 @ 08:37 am PDT

Hi everyone, thanks for all the comments on the article, the system and technical questions. I can release the latest development from the just completed concept design work for the String Transport STS 102, video is on youtube and at the site. http://sts21.com.au/Video.aspx



We welcome all your feedback!

The Commercialisation team at String Transport Systems Limited

Mike McBride
15th March, 2011 @ 10:41 pm PDT

This is a series of suspension bridges, a longer version of the Oakland Bay Bridge. The shape of those suspension cables is the efficient shape for such supports. The straight shape is impossible, with gravity around. Only a suspended roadway can eliminate the sharp peaks that would throw off any rapid vehicle. That was the key to wide use of such bridges, and they are still no good for concentrated loads like trains.

Bob Stuart
6th December, 2012 @ 04:39 pm PST
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