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Aerotrain: The High-Speed Train That Almost Revolutionized Transport

Aerotrain

Some of the fastest trains in service today have a top speed in excess of 200 miles per hour. With the exception of Shanghai maglev, all of them are conventional wheel-on-tracks system, which is remarkable because rolling friction has always been the biggest obstacle to high-speed travel. But if you want to see what the future has in store for rail travelers, just look at the world speed records—out of the top ten speed record holders, eight are maglev trains. The highest speed achieved by any train is an astounding 375 miles per hour (603 kmph) by a Japanese maglev train under development. The ability of maglev trains to eliminate rolling friction is what gives them their superior speed. Half a century ago, when research in maglev trains were just getting started, a French engineer proposed an entirely different system but based on the same concept of frictionless travel.

The engineer was Jean Bertin. While working to soundproof an aircraft engine, one of Bertin’s collaborators, Louis Duthion, discovered that when an aircraft is flying too close to the ground the air underneath the craft gets compressed producing an increased lift and decreased aerodynamic drag. This effect is known as “ground effect”. The phenomenon was well-known among pilots, but for Bertin and his team, it was entirely new.

Bertin realized that if the compressed air was contained under the craft by the means of an enclosure, it was possible to produce an air cushion over which the craft could glide with minimum resistance and power. Again, this idea was not new. As early as the 19th century, in 1860, another French engineer Louis Girard had imagined an air cushion train. Other attempts in the same direction but with different types of vehicles were made by the Americans, the Japanese and the British. But this didn’t disappoint Bertin. On the contrary, it encouraged him to continue researching on ground effect vehicles.

In 1958, British engineers made the first hovercraft, and on 25 July 1959, it made its first successful crossing of the English Channel. Throughout the 1960s, many improvements and breakthroughs in hovercraft technology was made allowing the new craft to be deployed in a wide range of military services, such as search and rescue, and in commercial operations. Small-scale ferry service across the English Channel started as early as 1962. By 1968, the hovercraft had developed into a useful commercial craft.

Aerotrain

Jean Bertin's assistant Paul Guienne presents a model of his prototype Aérotrain.

Meanwhile, Jean Bertin was making his own progress. He demonstrated that a “multi-skirt" approach, which used a number of smaller cylindrical skirts instead of one large one, like those on British hovercrafts, offered better stability to the craft. In the early 1960s, Bertin proposed the “Aerotrain”—a railway that ran on a cushion of air at very high speeds over a concrete monorail, like an “imprisoned airplane, flying without wings tight to the ground.”

At first, Bertin built scale models of his Aerotrain and tested them on the streets of Paris. After successfully demonstrating them to his sponsors, Bertin scaled the models up, first with a half-scale 30-foot version with room for four passengers and finally to a full-sized, 75-foot version with a car for 80 passengers.

In 1966, a 6.7-km-long test track was built in Gometz-le-Châtel, Essonne, France, re-using an abandoned railway trackbed. The first prototype, with a capacity of six seats, and equipped with a streamlined propeller resembled an airplane without wings. In a few months, it reached a record speed of 214 mph (345 kmph). Only 14 months later, Bertin readied a second prototype, powered by turbine-powered airscrew, and watched it touch 262 mph (422kph).

Aerotrain

Bertin convinced the French government to finance another test track, just outside the city of Orleans, situated about halfway between Paris and Bourges. The 18-kilometers-long nearly straight track is elevated on concrete pillars 5 meters above the ground. If the test was successful, it was expected that the tracks would be extended all the way to Paris. The track was completed in September 1969. Fiver years later, Bertin’s final model, the Aerotrain I80, broke the land speed record for railed vehicles, clocking 267 mph (430.4 kmph).

Bertin felt the technology was sufficiently realized for full implementation, and embarked on negotiations with the government for the construction of a network of monorails across France. But the government was not as confident, and there was concern that the state-owned railway network would suffer if the project went ahead. In 1974, the state withdrew financial support and the Aerotrain project was cancelled. Support shifted towards très grande vitesse, or TGV, instead—France’s other high-speed transport solution. The TGV would go on to become one of the world’s most successful high-speed rail network and among the world's most advanced. A TGV train also holds the world record for the fastest wheeled train, reaching 357.2 mph (574.8 km/h).

Aerotrain

Jean Bertin, who was already suffering from cancer and overworked after a decade of effort, died broken-hearted in December 1975. His company, Bertin Technologies, operates to this day on a wide range of technologies encompassing life sciences, environment, space and big science sectors.

The test track built outside Orleans still stands, mostly intact. The structure begins north of Orleans, from the commune of Saran, continues north along D2020, passes Chevilly, gets briefly interrupted by the A19—Paris’s outermost ring road—passes Artenay and ends abruptly in the middle of a field.

The first test track in Gometz-le-Châtel, Essonne, is also visible in the countryside, though it is mostly overgrown and parts have been removed when the land was redeveloped.

Aerotrain

A 1/12 scale model of Jean Bertin's Aérotrain.

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Engineer Jean Bertin shows a model of his prototype Aérotrain to Prime Minister Georges Pompidou in Paris.

Aerotrain

Aerotrain

Aerotrain

Aerotrain

Aerotrain

A 1/2 scale prototype on a test track at Gometz-le-Châtel, Essonne.

Aerotrain

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The elevated test tracks near Chevilly today.

Aerotrain

The elevated test tracks near Chevilly today.

Aerotrain

Part of the tracks through a patch of forest near Chevilly. Photo: jsmaur/Flickr

Aerotrain

Part of the test tracks in Gometz-le-Châtel, Essonne. Photo: ℍenry Salomé/Wikimedia Commons

References:
# Karel Vereycken, https://www.solidariteetprogres.org/IMG/pdf/karelvereycken.fr-aerotrain_high_speed_rail_and_nuclear_technology_the_lessons_of_jean_bertin.pdf
# Telegraph, https://www.telegraph.co.uk/motoring/4748859/How-the-future-was-cancelled.html
# Google Sightseeing, http://www.googlesightseeing.com/2013/10/frances-aerotrain/
# New Scientist, https://books.google.co.in/books?id=R0YnVUkTifgC&pg=PA500&lpg=PA500&dq=Jean+Bertin+hovercraft+multi+skirt
# Mashable, https://mashable.com/2016/01/22/aerotrain/

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