By Rory Carroll
SAN FRANCISCO Aug 12 (Reuters) - Billionaire U.S. entrepreneur Elon Musk unveiled plans on Monday for a futuristic "Hyperloop" transportation system to whisk passengers between San Francisco and Los Angeles in under half an hour.
The highly anticipated announcement put to rest some of the questions surrounding the ambitious project, which the Tesla Motors Inc founder and CEO has hinted at for months but declined to discuss in detail.
Musk said the Hyperloop would cost less than $6 billion in total and could transport 7.4 million people each way each year.
He said it would take 7-10 years for the project to be completed.
The solar-powered system, which Musk previously described as a cross between a Concorde, rail gun and air-hockey table, would shoot as many as 28 passengers in each enclosed capsule through a low-pressure steel tube at up to 800 miles per hour, according to the 57-page design plan.
Musk, who made his name as a PayPal founding member before going on to start SpaceX and Tesla, envisions capsules departing every 30 seconds and traversing the roughly 400 miles between Los Angeles and San Francisco - the busiest traffic corridor on the West Coast - along an elevated tube erected along the I-5 interstate highway.
The capsules ride a cushion of air blasted from "skis" beneath, propelled via a magnetic linear accelerator.
Major questions remain, notably whether the California state government will ever approve the massive project, and whether any private companies are willing to step in and build it. The design remains theoretical and has yet to be tested in the field.
Musk has said he is too busy running electric car company Tesla and rocket manufacturer SpaceX to build the Hyperloop himself. He said the design plans were open-source, meaning others can build on them.
On Monday, however, he told reporters on a conference call he could kick off the project.
"I've come around a little bit on my thinking here," he said.
"Maybe I could do the beginning bit... and then hand it over to somebody else," he said.
He said he would be willing to put some of his personal fortune toward the project but stressed that building the Hyperloop was a low priority for him as he continues to focus primarily on SpaceX and Tesla.
He also asked the public for help improving the design. Corporations have resorted in the past to public assistance on their products. In 2009, Netflix Inc awarded a cash prize to a team that succeeded in improving by 10 percent the accuracy of its system for movie recommendations.
Musk is floating the Hyperloop as an alternative to the state's planned high-speed train line, which he has said will be both too expensive to build and too slow.
Cost estimates for construction of the train line, a major priority of California Governor Jerry Brown's, have ballooned to $68 billion, far more than what Musk believes it will cost to build the Hyperloop.
The Hyperloop would be safer, faster, less expensive and more convenient, Musk said in a blog post.
The expected half-hour travel time for Hyperloop passengers compares with current travel times of an hour and 15 minutes by plane, about 5 and a half hours by car, as well as about 2 hours and 40 minutes via California's planned high-speed rail.