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What is the Hyperloop? Billionaire Elon Musk is finally telling us

Image: Hyperloop concept
Brent Couchman / John Gardi
Image: Hyperloop concept
Billionaire Elon Musk has held back on describing his Hyperloop concept for high-speed travel, but a couple of weeks ago, he said a plan laid out by John Gardi is the@BrentCouchman

After more than a year of buildup, brainy billionaire Elon Musk is finally ready to share the details about his "Hyperloop" high-speed transit concept.

"Pulled all nighter working on Hyperloop (as did others)." Musk, who heads the SpaceX rocket venture as well as the Tesla electric-car company, wrote in a Twitter update on Monday. "Hopefully not too many mistakes. Will publish link at 1:30 PDT [4:30 p.m. ET Monday].

Even Musk, who's no coward when it comes to big ideas, admits that building the Hyperloop is too big of a challenge for him to take on right now.

"I think I kinda shot myself in the foot by ever mentioning the Hyperloop, because I'm too strung out," he told Tesla investors last week. "Obviously I have to focus on core Tesla business, and SpaceX business, and that's more than enough."

He said he'd have to leave it to others to execute the Hyperloop concept as an open-source project, although he might pursue the idea more actively if no one picked up on it during the next few years.

Hints about the Hyperloop
Musk says that what he has in mind isn't a rail system. He calls the Hyperloop a "fifth mode" of transportation, distinct from planes, trains, automobiles and boats.

"It would work better than a high-speed rail, or a plane, between the right city pairs, like San Francisco and L.A., or New York-Boston," he told CNBC. A trip from S.F. to L.A. would take about a half-hour. Musk guessed that the system could be built for a tenth of the cost-per-mile associated with California's proposed $68 billion high-speed rail system, which won't be nearly as high speed as Japan's. During May's D11 Conference, he said the Hyperloop would be a "cross between a Concorde, a rail gun and an air hockey table."

Musk dropped some additional hints last Thursday during a Google+ Hangout on entrepreneurship, co-starring British billionaire Richard Branson:

  • Vehicles would travel "effectively faster than the speed of sound," Musk said. He noted that in order to get from San Francisco to Los Angeles in a half-hour, the average speed would have to be about 700 mph (1,127 kilometers per hour).
  • The Hyperloop concept "does involve a tube, but not a vacuum tube ... not frictionless, but very low friction."
  • The system is optimized to link pairs of cities that are less than 1,000 miles (1,600 kilometers) away from each other. "Once you get to the 1,000-mile range, you should just take a supersonic plane," Musk said.

CNBC: Hyperloop-type tech under development

Musk's Hyperloop hints sparked a lively guessing game among the entrepreneur's fans, who drew up "Futurama"-esque schemes to shoot capsules through elevated tubes, or push maglev cars through vacuum-sealed tunnels. The guessing game's leader is a self-described "tinker" named John Gardi, who tweeted out a chart for a turbine-driven pneumatic system that uses magnetic linear accelerators to rev up the Hyperloop's vehicles.

"Your guess is the closest I've seen anyone guess so far," Musk told Gardi last month in a Twitter update.

With that encouragement, Gardi went on to write a detailed construction plan for his Hyperloop concept, published last week on the Motherboard blog. Gardi told NBC News that he wasn't responding to requests for interviews, and preferred to use his Motherboard posting and Twitter account as the vehicles for discussion.

Reality check on the Hyperloop
Can the Hyperloop ever be built? The idea of using pneumatic tubes for rapid transit goes back to the 19th-century, when Alfred Ely Beach, an inventor and the editor of Scientific American, built a demonstration subway project in New York. And the era of high-speed rail travel, in the form of Japan's Shinkansen system and France's TGV network, is closing in on the 50-year mark.

But such grand projects have foundered in the United States, due to the expense of building new infrastructure and negotiating the rights of way, particularly in the country's urban centers. Emil Frankel, a former transportation official who is now a visiting scholar at the Bipartisan Policy Center, says the vision of criss-crossing America with bullet trains just isn't realistic anymore.

"I just can't imagine that in a time when we have these huge annual deficits," he told NBC News. "It seems far better to make improvements in our existing systems. One would like our trains to travel faster than they did in the 19th century, and many of them don't."

Whether it's the Hyperloop or high-speed rail, America needs something to beef up its transportation infrastructure, says Art Guzzetti, vice president of policy for the American Public Transportation Association. "We can't do it with airlines alone," he told NBC News.

The air vs. rail comparison seems to be an issue of perennial debate, but the fact that the benefits and drawbacks continue to be debated suggests that there's room for another approach to regional transportation. Maybe the Hyperloop is that approach.

"New ideas are always coming up," Guzzetti said. "I'm someone who is very interested in all of this stuff. New ideas are good."

However, Guzzetti says new ideas shouldn't be used as an excuse for holding up the high-speed rail initiatives that are already chugging along.

"Transportation is a huge issue for the economy," he said. "We're behind on our investments, and it would certainly be a mistake to cause any delay just because new ideas are coming. There is progress. It's not always visible, but now we're building up a little bit of momentum. We're always open to new ideas, but you don't want to hold up on the progress we're already making on projects that are so clearly needed."

More about Elon Musk's far-out ideas:

This is an updated version of a report originally published at 8:20 a.m. ET Aug. 8.

Alan Boyle is's science editor. Connect with the Cosmic Log community by "liking" the NBC News Science Facebook page, following @b0yle on Twitter and adding +Alan Boyle to your Google+ circles. To keep up with's stories about science and space, sign up for the Tech & Science newsletter, delivered to your email in-box every weekday. You can also check out "The Case for Pluto," my book about the controversial dwarf planet and the search for new worlds.