The Channel Tunnel was first proposed in Napoleon’s times in 1802, by French engineer Albert Mathieu-Favier. He envisaged an oil-lamp lit underground roadway for horsedrawn carriages with a halfway point on a sandbank-turned-island. It was an idea controversial with the British, who feared for national security. Little could Matthieu have imagined that 186 years later construction would begin on a passenger and freight train connection that would become the world’s longest underwater tunnel and third longest railway tunnel.
But the Channel Tunnel’s 37.9 km could be knocked into a cocked hat, if a proposal to dig a transatlantic tunnel were to go ahead, covering the 3,400 km separating the UK and the USA.
Under, over or floating in the middle?
Astonishingly, a transatlantic “chunnel” is not a new idea. In fact, various suggestions have been made over the last century about how a transatlantic tunnel could be made a reality. One concept is a tunnel dug directly under the sea bed like the Anglo-French solution, which would take an estimated 300 years to drill, would need to pass through underwater mountains and rifts, and require anti-earthquake technology to survive.
A tunnel that sits on the ocean floor, like the San Francisco BART, is a second possibility, except that the pressure at the Atlantic’s depths is 500 times that at the surface. Another proposal is a bridge-like tube in the air, above the sea. But the complications this might cause for shipping are huge.
Some say that an option falling somewhere in between would be a floating tunnel constructed from prefabricated sections and cables and sitting around 50 metres below the sea’s surface – that would allow trains to pass through, not be subject to the deadly pressure of the deep seas, and not interfere with shipping or be at the mercy of surface weather conditions.
Jets or electromagnets?
And how would the “shuttles” be propelled? Some say jet propulsion could work, leading to talk of London to New York commutes being doable in under an hour. However, after reaching top speeds the vehicle would need an estimated 18 minutes to decelerate.
Meanwhile, Elon Musk is a proponent of so-called maglev systems, where rolling stock is levitated by electromagnets to eliminate friction and so reach speeds of up to hundreds of kilometres per hour – but so far no maglev innovations of any significant length exist. The world’s longest so far is the Shanghai Maglev: covering 30 km in around 8 minutes, prior to 2021 it held the record for fastest train service in commercial operation with a top speed recorded at 431 km/h.
Given the logistics and above all the costs involved – an estimated 18.8 trillion euros – a transatlantic tunnel is not an idea with any political legs in the immediate future, but like Albert Matthieu, we can dream.
