It is called the Hyperloop and, according to its designer, it will be a revolutionary ''fifth mode'' of transport, eclipsing trains, planes, boats and automobiles.
The ''cross between Concorde, a rail gun and an air hockey table'' could deliver passengers between US cities faster than sound.
The history of transport is replete with dreamers with similar schemes. But the latest futuristic project, which has had the technology world buzzing for months, has one crucial difference. Its backer is a Silicon Valley wonder boy 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 before going on to launch spaceships. He also founded Tesla, which has made electric sports cars viable and profitable. He has been compared to the fictional character of Tony Stark, played by Robert Downey jnr , in the Iron Man series of films.
So when Mr Musk, 42, announced that he would be publishing plans for the Hyperloop on Monday, scientists were sent into a tailspin. Mr Musk posted his ''alpha design'' on the internet.
Mr Musk will not be patenting the solar-powered design and it will be ''open source'', meaning anyone can modify it, or try to build it.
Iron Man 2008. Tony Stark played by Robert Downey jnr.
Mr Musk has quashed speculation that 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, 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?''
Mr Musk replied, saying: ''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 about 2.7 metres in diameter, raised above the ground on pylons. 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.
Mr Musk's intended location for the first Hyperloop is California, between Los Angeles and San Francisco. His motivation for the project came from disillusionment with the Golden State's high-speed rail project, which has been dubbed the ''bullet train to nowhere'' after a series of setbacks. He believes the Hyperloop could deliver passengers between the two cities in just 30 minutes, compared with three hours for the bullet train.
Updated with link.