Elon Musk's Tubular Vision

Yesterday afternoon, Elon Musk finally gave details of the Hyperloop, his much-anticipated proposal to shoot people-moving pods through a tube linking Los Angeles and San Francisco. He argues that the system would cost US $6 billion if the pods were just large enough to carry people, or $10 billion if they had to carry cars as well.

These are wish-numbers, of course, and no project ever built ended up costing as little as its designers had wished. But the real number to beat is $70 billion, the sum the State of California is preparing to spend on a high-speed rail system that would poke along at a quarter the Hyperloop's claimed speed (fast enough to make the Los Angeles-to-San Francisco trip in 30 minutes). In a live-blogged press conference Monday afternoon, Musk maintained that his system would be economical in terms of both energy and money and that it would beat air travel for distances of less than 1500 kilometers (900 miles).

By saying that the Hyperloop would use only partially depressurized tubes, he ended speculation that it would achieve a complete vacuum to utterly eliminate air resistance. Such a design, which can attain an efficiency of acceleration now possible only in space craft, was worked out by the Rand Corp. back in the 1970s. As stated in an earlier IEEE Spectrum article, the Rand plan would get a traveler between any pair of major cities in the northern hemisphere within 90 minutes.

Musk said the Hyperloop would get its motive force from the alternating electromagnetic field of a linear electric motor. That's essentially the coil of a round motor that's been unwound and laid out on a strip; such a coil can recover energy from the car as it decelerates, allowing for a very efficient use of energy overall. To handle the to-and-fro traffic between the cities, Musk told Bloomberg Business Week, the system would have two tubes, one beside the other, like the twin barrels of a shotgun. To avoid land-use problems, the tubes would be elevated and would snake along an existing right-of-way: the I-5 freeway.

So, has Musk identified the next big thing in transportation, or is he just having a little fun with reporters starved for news in mid-August? One encouraging detail is the guy's declared willingness to bear some of the financial risk by creating a prototype for the Hyperloop. "I always invest my own money in companies I create," he said Monday. "I don't believe in the whole thing of just using other people's money."

However, he emphasized that his main priorities were still his two existing startups, Tesla Motors and SpaceX. "If it was my top priority, I could probably get it done  in 1 to 2 years," he said. "But it's going to be pretty far from my top priority."

Image: Tesla Motors

UPDATE: I explain the concept on Fox News:

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