Aérotrain

The Aérotrain was an experimental Tracked Air Cushion Vehicle
(TACV), or hovertrain, developed in France from 1965 to 1977 under the engineering leadership of Jean Bertin (1917–1975) – and intended to bring the French rail network to the cutting edge of land-based public transportation.

Though similar to a maglev design, which levitates a train car over a complex electromagnetic track to eliminate all resistance other than aerodynamic drag, the Aérotrain – also a "train without wheels" – rode on an air cushion over a simple reinforced concrete track or ''guideway'' and could travel at the speed of a maglev train, without the further technical complexity and expense of its track. In many respects, the entire concept resembled a product of the aircraft rather than rail industry.

History

In 1969, a U.S. company, Rohr Industries, licensed the Aérotrain technology to build the hovertrains in the United States. That same year the Aérotrain established the world record for a TACV, the pilots saying that with a longer track even higher speeds could have been reached without major difficulties. The final prototype, the ''Aérotrain I80'', set a world speed record in 1974 for overland air cushion vehicles, reaching a speed of and a peak speed of . The prototypes, which ultimately used twin turbine engines through a ducted propeller with seven blades, demonstrated they could accelerate and decelerate quickly, which offered a huge advantage of enabling effective service between tightly spaced stops.

US Secretary of Transportation John Volpe, the mayor of Los Angeles and representatives and transportation specialists from over 18 countries came to France and participated in test rides, studied the system and reported on the Aérotrain. Bertin felt the technology was sufficiently realized for full implementation, and the French government signed a contract to implement full-scale service on the outskirts of Paris, between Cergy and La Défense. The Aérotrain nonetheless ran into increasing internal conflicts with its client SNCF, which had no research and development department of its own and strongly favored improving the existing rail system.

Aérotrain faced numerous design challenges. The system would require new elevated guideways for every implementation – further pitting Aérotrain against efforts to improve existing "wheeled" rail system. Bertin's Versailles-based companies, Bertin and Co and Aeroglide Systems, worked to resolve issues with sudden changes in air pressure, as when the train would pass another train or enter a tunnel. Prototypes used gas turbines with giant propellers, which created tremendous noise both inside and outside the train car itself – and thus required reduced speeds in urban areas. SNCF felt they already had trains that could run at those reduced speeds. Proponents pointed out electric linear induction motors could make the TACV silent. Eventually SNCF simply opposed the project, citing a broad litany of concerns.

In 1974, after his election as President of France, Valéry Giscard d’Estaing formally annulled the contract for the Aérotrain Cergy-La Défense line and SNCF formally shifted support to the TGV as its high-speed ground-transportation solution. Notably, D'Estaing's wife was the granddaughter of Eugène Schneider, founder of what became an international syndicate, Schneider Group. Noted Belgian journalist Karel Vereycken pointed out: "the Schneider dynasty have been and are still a pillar of the history of the French railroad and steel industry. Hence, the innovation of the Aérotrain (to be built by the aircraft industry) would not, in the short run, have made them more wealthy and one can easily imagine that a train without wheels does not get much enthusiastic approval of the feudal wheel producers." Rohr abandoned the technology in 1975.

Test tracks

Most of the track for the Aérotrain was constructed of ferroconcrete to provide an inverted "T" shape for the monorail, with the tracks ultimately used only for experimental purposes.

*The first test track was long and was built in February 1966 in Gometz-le-Châtel, Essonne