The “cross between Concorde, a rail gun and an air hockey table” will deliver passengers between US cities faster than the speed of sound.
The history of transport is replete with dreamers who have concocted such schemes for getting people from A to B in previously unimagined haste. And many of them have remained just that, impractical ideas on a drawing board that will never see the light of day.
But the latest mysterious project, which has had the technology world buzzing for months, has one crucial difference. Its backer is a Silicon Valley wunderkind with a proven track record of turning science fiction into reality.
Billionaire Elon Musk’s CV is impressive, to say the least. He made his initial fortune from PayPal, the online secure payment system, before going on to launch spaceships. Last year his SpaceX venture became the first private operation to dock a cargo capsule with the International Space Station.
Back on Earth, Mr Musk also founded Tesla, which has made electric sports cars viable and profitable.
The mercurial, fictional character of Tony Stark, played by Robert Downey Jr in the Iron Man films, is reputedly based on him.
So when Mr Musk, 42, announced that he would be publishing plans for the Hyperloop on Monday, August 12 – tomorrow – scientists were sent into a tailspin.
They will have to wait for Mr Musk to post his “alpha design” on the internet then but he has dropped several hints about its features, including that the system will be powered by solar panels.
Mr Musk will not be patenting the design and it will be “open source”, meaning anyone can modify it, or try to build it.
The fevered speculation about what it would actually look like has ranged from wild theories on Star Trek-style teleportation to more achievable ones involving cars being pushed through vacuum sealed tunnels using magnets.
Mr Musk has denied it will be a so-called “vactrain”, a concept that is already being pursued by a company in Colorado. His idea “does involve a tube, but not a vacuum tube”, he said, adding: “Not frictionless, but very low friction.”
In recent weeks a large part of the mystery appeared to have been solved. A technology enthusiast in Canada called John Gardi published a diagram of how the Hyperloop might work. He went on to ask Mr Musk on Twitter: “Can you give me some basic clues? What diameter of tube so I can start designing stations and throughways?”
To his extreme surprise Mr Musk replied: “Your guess is the closest I’ve seen anyone guess so far. Pod diameter probably around 2m.”
Mr Gardi, who describes himself modestly as a “tinkerer”, came up with a tunnel 9ft in diameter, raised above the ground on pylons. His tube could be made from materials already used for sewer pipes. It would form a continuous loop between two destination points. Giant turbines would blast a stream of air into the tube. The two-metre wide pods, carrying people, would be moved by a rail gun – a tube that uses magnets to accelerate material passing along it.
As they approach their journey’s end they would be routed out of the air stream and slowed down using a magnetic braking system.