||This article may contain original research. (January 2011)|
A transatlantic tunnel is a theoretical tunnel that would span the Atlantic Ocean between North America and Europe possibly for such purposes as mass transit. Some proposals envision technologically advanced trains reaching speeds of 500 to 8,000 kilometres per hour (310 to 5,000 mph). Most conceptions of the tunnel envision it between the United States and the United Kingdom ‒ or more specifically between New York City and London. The main barriers to constructing such a tunnel are cost with estimates of between $175 billion to $12 trillion as well as the limits of current materials science.
A transatlantic tunnel would be 88 times longer than the Gotthard Base Tunnel and 36 times longer than the Delaware Aqueduct. In 2003, the Discovery Channel's show Extreme Engineering aired a program entitled "Transatlantic Tunnel", which discussed the proposed tunnel concept in detail.
Proposed tunnels 
Many variations of the concept exist, including a tube above the seabed, a tunnel beneath the ocean floor, or some combination of the two.
A 1960s proposal has a 3,100 miles (5,000 km)-long near-vacuum tube with vactrains, a theoretical type of maglev train, which could travel at speeds up to 5,000 miles per hour (8,000 km/h). At this speed, the travel-time between New York City and London would be less than one hour. Another modern variation, intended to reduce costs, is a submerged floating tunnel about 160 feet (49 m) below the ocean surface, in order to avoid ships, bad weather, and the high pressure associated with a much deeper tunnel near the sea bed. It would consist of 54,000 prefabricated sections held in place by 100,000 tethering cables. Each section would consist of a layer of foam sandwiched between concentric steel tubes, and the tunnel would also have reduced air pressure. The cables would be anchored to the sea floor, and would have room to sway if a submerged object such as a submarine were to hit the tunnel. If a breach were to occur somewhere along the tunnel, the breached section could be isolated by titanium pressure-lock doors. If such a breach were to occur behind a train travelling in the tunnel, the train would be travelling faster than any incoming water, and could therefore escape the breached section before the doors needed to be closed. If, on the other hand, a breach were to occur in front of a fast-moving train, it might not have enough time to slow down to avoid hitting the incoming water or the isolating doors, thus resulting in a major crash (at up to 5,000 mph), probably destroying several sections of the tunnel.
Jet propulsion 
Ideas proposing rocket, jet, scramjet, and air-pressurized tunnels for train transportation have also been put forward. In the proposal described in the Extreme Engineering episode, trains would take 18 minutes to reach top speed, and 18 minutes at the end to come to a halt. During the deceleration phase, the resultant 0.2g acceleration would lead to an unpleasant feeling of tilting downward, and it was proposed that the seats would individually rotate to face backwards at the midpoint of the journey, in order to make the deceleration more pleasant. However, spinning chairs would also cut down considerably on passenger capacity, and would also be expensive, therefore raising the cost per ticket to a much higher level.
Mixed undersea and overland route 
A proposed 6000-km alternative route, mixing undersea and overland travel, would head north from Newfoundland over the ice sheet of Greenland and across Iceland to the Faroe Islands and then Scotland. It is thought that this route would be cheaper to build, because it could have multiple tunnel heads, but would also be more difficult to construct, owing to adverse weather conditions in northern regions. Moreover, while lessons learned from the Trans-Alaska Pipeline System might mitigate many difficulties, building a railway over an ice sheet would present particular engineering challenges. Roads built on ice sheets do exist in a few places, such as Svalbard and Antarctica, but there are problems at the edge of the sheet and due to ice streams. Unlike a roadway, a high-speed railway must be stable, and would prove particularly difficult and costly to maintain where it crossed the ice sheet.
Early interest 
Suggestions for such a structure go back to Michel Verne, son of Jules Verne, who wrote about it in 1888 in a story entitled Un Express de l'avenir (An Express of the Future). This story was published in English in Strand Magazine in 1895, where it was incorrectly attributed to Jules Verne, a mistake frequently repeated today. In 1913, the novel Der Tunnel was published by German author Bernhard Kellermann. It inspired four films of the same name: one in 1914 by William Wauer, and separate German, French, and British versions released in 1933 and 1935. The German and French versions were by Curtis Bernhardt, and the British one was written in part by science fiction writer Curt Siodmak. Perhaps suggesting contemporary interest in the topic, an original poster for the American release of the British version (renamed Transatlantic Tunnel) was, in 2006, estimated for auction at $2,000–3,000.
Modern research 
Robert H. Goddard, the father of rocketry, was issued two of his 214 patents for the idea. Arthur C. Clarke mentions intercontinental tunnels in his 1956 novel The City and the Stars. Harry Harrison's 1975 novel Tunnel Through the Deeps (also published as A Transatlantic Tunnel, Hurrah!) describes a vacuum/maglev system on the ocean floor. The April 2004 issue of Popular Science suggests that a transatlantic tunnel is more feasible than previously thought, and without major engineering challenges. It compares it favorably with laying transatlantic pipes and cables, but with a cost of 88 to 175 billion dollars.
- Joseph Giotta (Narrator), Powderhouse Productions (16 April 2003). "Transatlantic Tunnel". Extreme Engineering. Discovery Channel. http://dsc.discovery.com/convergence/engineering/transatlantictunnel/interactive/interactive.html.
- Carl Hoffman (12 April 2004). "Trans-Atlantic MagLev: Vacuum Tube Train". Popular Science. Retrieved 27 September 2011.
- Michel Verne (November 1895). "An Express of the Future". The Strand Magazine. Retrieved 2008-08-02.
- Michael Rodman (Summer 2002). "Tunnel Vision". Harvard Law Bulletin, Harvard University. Retrieved 2007-09-12.
- "Lot 28748, Auction 636: The Transatlantic Tunnel (Gaumont, 1935). One Sheet (27" X 41")". Heritage Auction Galleries. July 11, 2006. Retrieved 2008-11-10.
- Jeffrey Kluger (March 29, 1999). "TIME 100: Robert Goddard". Time. Retrieved 2007-12-28.
- "Part I: Chemical Propulsion and the Dawn of Rocket Science". The Past and Future of Rocket Engine Propulsion. Regents of the University of Michigan. 2002. Retrieved 2007-12-28.
- Stuart Carter (11 November 2000). "Harry Harrison: A Transatlantic Tunnel, Hurrah!". Infinity+. Retrieved 2007-09-12.