A solar-powered supertrain that can travel close to the speed of sound is to be developed in the latest project by the billionaire PalPal founder Elon Musk.
The "hyperloop" train will complete the 350-mile journey from Los Angeles to San Francisco in 30 minutes, said Musk, leaving "all current technologies in the shade". The speed of sound is 768mph.
Musk, 41, is the founder of SpaceX, which builds rockets that carry cargo to the International Space Station, and electric car manufacturer Tesla Motors.
He said the Hyperloop would be a cross between Concorde, an electromagnetic "railgun" launcher currently in development by the US navy, and an "air-hockey table" where objects move on a pad of air.
Musk has given few clues as to the details of the bullet train project, but scientists speculate the system could be built in an underground pneumatic tube in California. Other believe it will involve propelling capsules down tunnels on waves of air, the Sunday Times reported.
"How would you like something that can never crash, is immune to weather, and goes three or four times faster than the bullet train," Musk asked delegrates at a conference in Los Angeles last year.
"It goes an average speed of twice what an aircraft would do. You would go from downtown LA to downtown San Francisco in under 30 minutes.
"It would cost you much less than an air ticket or any other mode of transport. I think we could actually make it self-powering. If you put solar panels on it, you generate more power than you would consume in the system.
"There's a way to store the power so it would run 24/7 without using batteries. Yes, this is possible, absolutely."