DESPITE its name, that famous old steam engine the Flying Scotsman never
flew鈥攂ut now engineers in Japan are developing trains that really do fly.
Using the 鈥渨ing-in-ground鈥� (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 8.1-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.
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The track is flat with containing walls on either side. 鈥淎 wing-in-ground
effect is also produced where the vertical fins meet the retaining wall,鈥� says
Yasuaki Kohama who heads the research project. 鈥淪o steering the Aerotrain is
virtually automatic.鈥�
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. 鈥淚f 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鈥檛 utilise the optimum plane of the ground effect.鈥� 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 3.6 grams of carbon dioxide per person
per kilometre, compared with 12.2 grams for maglev trains.
Japan鈥檚 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鈥檚 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.
