LOS ANGELES (AP) -- Billionaire entrepreneur Elon Musk released rough plans last week for a "Hyperloop" that would shoot capsules full of people at the speed of sound through elevated tubes connecting Los Angeles and San Francisco. Then he urged the public to improve on them.
Now the race is on.
A U.S. firm hustled out a model using a 3-D printer. Another company is testing a virtual Hyperloop with sophisticated computer software. In San Francisco, enthusiasts interested in "making Hyperloop a reality" will meet over beers.
Meanwhile, Musk himself has put aside the project and returned to his established transportation ventures: luxury electric car maker Tesla Motors Inc. and the rocket-building company SpaceX.
In principle, the Hyperloop is possible.
The concept pulls together several proven technologies: Capsules would float on a thin cushion of air and draw on magnetic attraction and solar power to zoom through a nearly air-free tube. Because there would be so little wind resistance, they could top 700 mph (1,125 kph) and make the nearly 400-mile (643-kilometer) trip in about half an hour.
Actual construction would hinge on challenges far more complex than advanced engineering — those involving money and politics.
Musk projected a $6 billion cost, but some say that's too low. Others suggested his timeframe of a decade to completion was naive — that getting political backing and environmental clearances, much less land to build the tubes on, would be hugely time-consuming.
Conspicuously absent was a commitment that Musk would sink substantial money into the project anytime soon — if ever. On a call with reporters, Musk suggested he might build a "subscale" test version in a few years if the idea was floundering.
One thing Musk was clear about: The public should participate in questioning, modifying and, ultimately, perfecting his proposal.
And in that respect, there has been no lack of enthusiasm.
At the computer simulation software firm ANSYS, engineers are designing and testing a virtual model.
Sandeep Sovani, the company's director of Global Automotive Industry, said he has long been intrigued by tube travel (an idea that predates the Hyperloop by a century) and wanted to do a model both out of intellectual curiosity.