Despite its name, that famous old steam engine the Flying Scotsman never flew-but now 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.
The WIG effect can be seen when you drop a sheet of paper and it scoots along the floor. In the same way, the absence of any friction besides wind resistance on a train would mean that little power would be needed to maintain forward momentum.
An 8á1-metre research model called the Aerotrain has just been tested at the Tohoku University Institute of Fluid Science in Sendai. It has two pairs of wings fore and aft, each with vertical stabilising fins on the end. The model is not fitted with a motor but has to be pushed along a semi-enclosed track by a truck. During recent tests, it lifted off using the WIG effect after reaching a speed of 50 kilometres per hour.
The track is flat with containing walls on either side. "A wing-in-ground effect is also produced where the vertical fins meet the retaining wall," says Yasuaki Kohama who heads the research project. "So steering the Aerotrain is virtually automatic."
For years, Russia has pioneered WIG-effect vehicles at sea, and Kohama has met Russian engineers to study their techniques. He says a land-based system is much more energy-efficient. "If you get closer to the surface then you get much more efficiency. At sea you are in danger of being hit by waves, so you can't utilise the optimum plane of the ground effect." Without having to worry about waves, Kohama says his land-based Aerotrain can fly between 5 and 10 centimetres above the ground.
He says the next step will be to reduce the speed at which the Aerotrain lifts off, so that the amount of time in contact with the track is kept to a minimum. That will cut friction and therefore overall energy consumption. The goal is to reduce pollution emissions to 3á6 grams of carbon dioxide per person per kilometre, compared with 12á2 grams for maglev trains.
Japan's government-backed maglev linear motor train project requires electromagnets along its entire track and has high power consumption. Kohama hopes that the Aerotrain will be so energy-efficient that it will eventually be powered by renewable energy sources such as solar panels on top of the track walls or wind turbines lining the route.
Kohama's team is now preparing to build a working model fitted with three pairs of wings and two pairs of propellers (see Diagram), so that it can power itself to speeds of 150 kilometres per hour. After that, the team wants to build a six-passenger model capable of reaching 300 km/h, and by 2020 a 335-passenger model that can travel at 500 km/h.
Reporter: Peter Hadfield, Tokyo
New Scientist issue: 11th March 2000
PLEASE MENTION NEW SCIENTIST AS THE SOURCE OF THIS STORY AND, IF PUBLISHING ONLINE, PLEASE CARRY A HYPERLINK TO: http://www.newscientist.com