Elon Musk, the entrepreneur behind PayPal, Tesla Motors Inc (NASDAQ:TSLA) and SpaceX, has released details about his proposed mass transit system, the Hyperloop. Musk has mentioned that he wanted to find something more efficient than rail for intercity travel, and people have been waiting for nearly a year for him to release his exact plans.

Tesla Elon Musk Hyperloop

The project started when the State of California announced that it would build a rail system connecting San Francisco and Los Angeles for $70 billion, assuming everything went according to plan. But when Musk looked at the details of the plan, he was unimpressed.

“The underlying motive for a statewide mass transit system is a good one. It would be great to have an alternative to flying or driving, but obviously only if it is actually better than flying or driving,” Musk wrote on his blog. “The train in question would be both slower, more expensive to operate (if unsubsidized) and less safe by two orders of magnitude than flying, so why would anyone use it?”

Musk knew that for mass transit to really work it had to be better than what already existed: cheaper, faster, safe during an earthquake, and it should rely mostly on renewable energy.

Hyperloop’s new combination of existing technology

What he came up with is a new take on an old idea: vacuum tubes, like the ones you would use at a bank’s drive-through, big enough to transport people. According to Musk, you could even build the Hyperloop large enough to accommodate vehicles.

Other people have approached this idea before, and Musk himself mentions Robert Goddard’s proposal to the Rand Corporation as an inspiration, but this design has two significant advantages. First, it relies on low pressure instead of an actual vacuum for propulsion, easing the design specifications and lowering the cost. Second, he would use an air cushion to levitate the pods slightly. “He has separated the air cushion and the linear induction drive, and that seems new,” said UCLA physics professor Martin Simon.

Tesla’s Elon Musk will develop first prototype personally

As with any big idea, Musk’s Hyperloop is coming in for scrutiny, as it should. The price tag would be in the neighborhood of $10 billion, and the untested technology would hurdle passengers along at speeds approaching 800 miles per hour, so a cautious skepticism seems warranted. But the each component of the Hyperloop has already been used in other applications.

“It does sound like it’s all done with known technology,” says Simon. “It’s not like he’s counting on something brand new to be invented.”

Musk originally said that he would let others take the lead on construction, opening himself up to accusations of not standing behind his own idea, but has since changed his mind, saying that he would develop a prototype as a proof of concept.