The ProposalThe proposal is as exotic as it is audacious: Get on a train at New York City’s Penn Station and hit Paris, London or Brussels just an hour later. “From an engineering point of view there are no serious stumbling blocks,” says Ernst Frankel, retired professor of ocean engineering at MIT. To do so, however, The Trans-Atlantic MagLev, as it is called, is going to have to employ Mag-lev technology like it has never been employed before.
The Technology
Magnetic levitation transport, or maglev, is a form of transportation that suspends, guides and propels vehicles via electromagnetic force. This method can be faster and more comfortable than wheeled mass transit systems. Maglevs could potentially reach velocities comparable to turboprop and jet aircraft (500 to 580 km/h). Maglevs have operated commercially since 1984. However, scientific and economic limitations have hindered the proliferation of the technology.
Maglev technology has minimal overlap with wheeled train technology and is not compatible with conventional railroad tracks. Because they cannot share existing infrastructure, maglevs must be designed as complete transportation systems. The term “maglev” refers not only to the vehicles, but to the vehicle/guideway interaction; each being a unique design element specifically tailored to the other to create and precisely control magnetic levitation and propulsion.
Due to the lack of physical contact between the track and the vehicle, the only friction exerted is that between the vehicles and the air. Consequently maglevs can potentially travel at very high speeds with reasonable energy consumption and noise levels. Systems have been proposed that operate at up to 650 km/h (404 mph), which is far faster than is practical with conventional rail transport. The very high maximum speed potential of maglevs make them competitors to airline routes of 1,000 kilometres (600 miles) or less. The world’s first commercial application of a high-speed maglev line is the IOS (initial operating segment) demonstration line in Shanghai that transports people 30 km ( 18.6 miles) to the airport in just 7 minutes 20 seconds (top speed of 431 km/h or 268 mph, average speed 250 km/h or 150 mph). Other maglev projects worldwide are being studied for feasibility.
The Next Step
The statistics and the limitations for traditional maglevs, however, do not even begin to apply to the Trans-Atlantic MagLev. To complete the 3471 miles (5588 km) from New York to London in under and hour the proposed system would have to reach speeds in excess of 5000 mph (8050 kmph), equal to Mach 7 and much faster than the jetliners of today. The statistics above show that those kind of speeds have never been reached yet. So what was Ernst Frankel saying when he talked of the absence of engineering stumbling blocks? This is where it gets really weird.
The limiting factors for the speed of a train are Rolling Resistance and Air Resistance. Rolling Resistance is the resistance between the wheels and the track and its limit will tell us the maximum speed the train can achieve without losing traction with the track. For traditional Mass Rail Transit (MRT) systems it is Rolling Resistance that is the constraining factor. Maglev trains eliminate Rolling Resistance as they have no actual physical contact with the guiding tracks they run on. Maglev trains are limited by Air Resistance and something called Magnetic Drag; although because Magnetic Drag is inversely proportional to the speed of the train it becomes less significant as speeds increase. Air Resistance, however, is proportional to the square of the speed of the train and is a significant limiting factor at high speeds.
Vactrains
The Trans-Atlantic plans to use a set of technologies called Evacuated Tube Technologies (ETT) to run the Maglev in conditions of vacuum, thereby eliminating all Air Resistance in one fell swoop. ETT-employing MRT systems are also called Vactrains. As far back as the late 19th century, proposals were made for a non-evacuated transatlantic tunnel linking the United States and Great Britain. This idea was highlighted in the 1933 German film Der Tunnel, remade as the 1935 British film Transatlantic Tunnel.
The modern concept of a vactrain, with evacuated tubes and maglev technology, was pioneered in the 1910s by American engineer Robert Goddard, who designed detailed prototypes while a university student. His train would have travelled from Boston to New York in 12 minutes, averaging 1000 mph. The train designs were found only after Goddard’s death in 1945.
Vactrains made headlines during the 1970s when a leading advocate, Robert F. Salter of RAND, published a series of elaborate engineering articles in 1972 and again in 1978. At the time, national prestige was an issue as Japan had been operating its showcase bullet train for several years and maglev train research was hot technology. The American Planetran would establish trans-planetary subway service in the United States and provide a commute from Los Angeles to New York City in one hour. The tunnel would be buried to a depth of several hundred feet in solid rock formations. Construction would make use of lasers to ensure alignment and use tungsten probes to melt through igneous rock formations. The tunnel would maintain a partial vacuum to minimize drag. A trip would average 3000 mph and subject passengers with forces up to 1.4 times that of gravity, requiring the use of gimballed compartments. Enormous construction costs (estimated as high as US$1 trillion) were the primary reason why Salter’s proposal was never built.
The Transatlantic Tunnel
Recent vactrain proposals by Frank Davidson, a founding member of the Channel Tunnel project, and Japanese engineer Yoshihiro Kyonati have tackled the transoceanic problems by floating a tube above the ocean floor, anchored with cables. The transit tube would remain at least 100 feet below the ocean surface to avoid water turbulence.
The Transatlantic Tunnel is proposed to use a submerged floating tunnel which uses the same techniques as that of a submarine. The same idea is also being proposed for cars to use in crossing the fjords in Norway. The tunnel would be held in place by using 100,000 large tethering cables. The tunnel would be built using 54,000 prefabricated sections. The sections would consist of a layer of steel surrounding a layer of foam surrounding another layer of steel. If ever built it would be the largest and most expensive construction project in history.
Three types of maglev technology
There are three primary types of maglev technology:
electromagnetic suspension (EMS) relies on feedback controlled electromagnets. Example: Transrapid
electrodynamic suspension (EDS) relies on superconducting magnets. Example: JR-Maglev.
Inductrack relies on permagnets.
Pros and Cons of different technologies
Each implementation of the magnetic levitation principle for train-type travel involves advantages and disadvantages. Time will tell as to which principle, and whose implementation, wins out commercially.
Technology
Pros
Cons
EMS
(Electromagnetic)
EMS is a propulsion system that trains do not have to carry; can attain very high speeds (500 km/h); magnetic fields inside and outside the vehicle are insignificant; highly reliable computer controlled operations; proven, commercially available technology
Guideway includes stator packs along entire length which adds to cost of construction, but do enable high speeds without vehicle weight penalty. Using Electromagnets, the space between the vehicle and the guideway is small (around 10mm) and must be constantly monitored and corrected by computer systems to avoid collision due to the unstable nature of electromagnets.
Superconducting EDS
(Electrodynamic)
Powerful onboard superconducting magnets enable highest recorded train speeds (581 km/h) and heavy load capacity; has recently demonstrated (Dec 2005) successful operations using high temperature superconductors (HTS) in its onboard magnets, cooled with inexpensive liquid nitrogen
Strong magnetic fields onboard the train make the train inaccessible to passengers with pacemakers or magnetic data storage media such as hard drives and credit cards; vehicle must be wheeled for travel at low speeds; system per mile cost still considered prohibitive; the system is not yet out of prototype phase.
Inductrack System
(Permanent Magnets)
Failsafe Suspension - no power required to activate magnets; can generate enough force at low speeds (around 5 km/h) to levitate maglev train; in case of power failure cars slow down on their own in a safe, steady and predictable manner before coming to a stop
Requires wheels. New technology that is still under development (as of 2006) and has as yet no commercial version or full scale system prototype.
The Inductrack and the Superconducting EDS are only levitation technologies. In both cases, vehicles need some other technology for propulsion. A Jet engine and a linear motor are being considered, such as the linear motor used for propulsion in the Japanese Superconducting EDS MLX01 maglev.
The German Transrapid electromagnetic maglev uses a linear motor for both levitation and propulsion.
Neither Inductrack nor the Superconducting EDS are able to levitate vehicles at a standstill, although Inductrack provides levitation down to a much lower speed. Wheels are required for both systems. EMS systems are wheel-less.
The German Transrapid, Japanese HSST (Linimo), and Korean Rotem maglevs levitate at a standstill, with electricity extracted from guideway using power rails for the latter two, and wirelessly for Transrapid. If guideway power is lost on the move, the Transrapid is still able to generate levitation down to 10 km/h speed, using the power from onboard batteries. This is not the case with the HSST and Rotem systems. It is not yet clear which of EDS and Inductrack the Trans-Atlantic MagLev proposes to use.
As envisioned by Frankel and Frank Davidson, a former MIT researcher and early member of the first formal English Channel Tunnel study group, sections of neutrally buoyant tunnel submerged 150 to 300 feet beneath the surface of the Atlantic, then anchored to the seafloor-thereby avoiding the high pressures of the deep ocean. Then air would be pumped out, creating a vacuum, and alternating magnetic pulses would propel a magnetically levitated train capable of speeds up to 4,000 mph across the pond in an hour. As Frankel and Davidson say, it’s doable. “We lay pipes and cables across the ocean every day,” says Frankel. “The Norwegians recently investigated submerged, floating tunnels for crossing their deep fjords, and were only held back by the costs.”
The Costs
Ah, the costs: Estimates range from $25 million to $50 million per mile. Another hurdle: safety. But Davidson believes a test case might mitigate concerns. “Maybe a tunnel across Lake Ontario would show how it reacts to dynamic conditions and give us a better understanding of the costs,” he muses. “A transatlantic tunnel will be done. We just have to be as interested in it as we are in getting to the Moon.”
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