Why Elon Musk’s ‘hyperloop’ won’t work
By Chris Woodyard and Roger Yu Gannett News Service August 13, 2013 7:32PM
The world has had a day to digest Tesla and SpaceX CEO Elon Musk’s proposal of a “hyperloop,” a high-speed train that would shoot pods through a tube with air pressure at speeds that would take people from Los Angeles to San Francisco in 30 minutes.
And he is mostly being hailed as a visionary, an example of the kind of can-do spirit that America needs.
But not all think the idea he is supporting is feasible — pointing out that traveling faster than a jet aircraft in a tube would be really, really difficult.
After reading Musk’s 57-page proposal, Sam Jaffe, senior research analyst at clean technology firm Navigant Research, was impressed with Musk’s willingness to release the report with “excruciating detail” and openly invite criticism. “What he’s done is amazing. He wrote it and said, ‘Criticize this,’” Jaffe says. “And it’s worthy of being criticized.”
Jaffe responded with some of his doubts about the plan. The biggest hurdle would be dealing with the temperature of air compression, says Jaffe, who has launched a start-up business in compressed-air energy storage.
While Musk’s estimates are thermodynamically correct, he says, “The heat of compression is always underestimated by engineers.”
“To take that heat away from the critical parts of the system, you need a lot of surface area inside the pod. You just have a limited volume of space to work with,” he says. “That’s what concerns me.”
Musk proposes a water tank that is attached to the pod and used as coolant. The steam generated from the process would be collected and released at stations.
Jaffe says that the pods may not be able to carry enough water. “That’s not an elegant solution. A lot of things worry me about that. It’s a hard engineering problem to solve whenever you’re pressuring air.”
Also, engineering hurdles: The pods would be under a lot of stress. And if the tube structure is elevated, it could be subject to buffeting by wind.
Musk’s idea isn’t new. Ever since pneumatic tubes using negative air pressure to shoot capsules showed up decades ago -- department stores used them for transactions, and newspapers used them to carry stories from the newsroom to operators who would produce metal type for the printing presses — people have dreamed of traveling through cylinders at high speed.
Jay Yarow, writing for Business Insider, says a similar idea for transporting passengers was hatched 41 years ago by a RAND Corp. researcher, R.M. Salter. He called his hyperloop a “Very High Speed Transit System,” or VHST. It, too, depended on trains suspended on air running through tubes. He says it faced technical challenges, but there were no apparent insurmountable barriers. His system would have been airtight, unlike Musk’s.
The idea went nowhere.
And Musk is not proposing to take on this futuristic train idea himself, having enough on his plate now with his Tesla car company and SpaceX space technology company. While he put his own fortune on the line for those, Musk will be sitting back to see whether his support helps get this hyperloop idea advanced in the hands of others.
Gannett News Service