In the months since Musk first mentioned the Hyperloop, there has been plenty of speculation. Critics, dealing with limited information, have contended that the specifications laid out by Musk would be nearly impossible to achieve. Such a long, pressurized tube would require an immense amount of energy while also producing tons of air friction and heat.
Now Musk argues that the Hyperloop represents a type of middle ground that other people have yet to consider. Instead of being a complete vacuum or running at normal conditions, the Hyperloop tubes would be under low pressure. “I think a lot of people tended to gravitate to one idea or the other as opposed to thinking about lower pressure,” Musk says. “I have never seen that idea anywhere.”
Inside the tubes, the pods would be mounted on thin skis made out of inconel, a trusted alloy of SpaceX that can withstand high pressure and heat. Air gets pumped through little holes in the skis to make an air cushion, Musk says. The front of the pod would have a pair of air jet inlets — sort of like the Concorde. An electric turbo compressor would compress the air from the nose and route it to the skis and to the cabin. Magnets on the skis, plus an electromagnetic pulse, would give the pod its initial thrust; reboosting motors along the route would keep the pod moving. And: no sonic boom. With warm air inside the tubes and high tailwinds, the pods could travel at high speeds without crossing the sound barrier. “The pod can go just below the speed of sound relative to the air,” Musk says.
So, science, or science fiction? About a dozen people at Tesla and SpaceX have helped Musk with the design and checked the physics behind the Hyperloop. I briefed Martin Simon, a professor of physics at UCLA, on some of the Hyperloop details, and he declared it feasible from a technological standpoint: “It does sound like it’s all done with known technology. It’s not like he’s counting on something brand new to be invented.”
Simon points out that the acceleration methods proposed by Musk are used at amusement parks to get a roller coaster going. Other companies have looked at these techniques for passenger and freight vehicles. What sets the Hyperloop apart, though, is the use of the air cushion to levitate the pods. “He has separated the air cushion and the linear induction drive, and that seems new,” Simon says, adding, “It would be cool if they had transparent tubes.”
The critics of California’s high-speed rail may be dismayed to learn that Musk does not plan to commercialize the Hyperloop technology for the time being. He’s posting the plans and asking for feedback and contemplating building a prototype. “I’m just putting this out there as an open source design,” he says. “There are sure to be suggestions out there for making this better, correcting any mistakes, and refining the design.” Musk maintains that he has too much on his plate to deal with bringing the Hyperloop to fruition. “I wish I had not mentioned it,” he says. “I still have to run SpaceX and Tesla, and it’s fucking hard.”
Musk says he would support another person or organization that wanted to make the Hyperloop a reality.
“It is a question of finding the right person and team to get behind it,” Musk says. “Creating a prototype is not that expensive.” But if no one advances or acts on Musk’s ideas, he may come back to the Hyperloop in a few years’ time and pursue it as part of Tesla. “Down the road, I might fund or advise on a Hyperloop project, but right now I can’t take my eye off the ball at either SpaceX or Tesla.”
Copyright 2013 Bloomberg