Hyperloop, explained

Doug Aamoth has a Time article about the Hyperloop:

Elon Musk, he of Tesla and SpaceX fame, is looking to shake up the transportation industry with an idea called the Hyperloop. Here are the basics:

Musk proposes the roughly 380-mile trip from Los Angeles to San Francisco taking about 35 minutes in the Hyperloop. Aluminum “pods” containing passengers and even cars would be shot through steel tubes at almost eight hundred miles per hour in certain stretches. Musk’s blog post mentions that such a system would be “the right solution for the specific case of high-traffic city pairs that are less than about nine hundred miles apart.”
In Musk’s vision, the Hyperloop would transport people via aluminum pods enclosed inside of steel tubes. He describes the design as looking like a shotgun with the tubes running side by side for most of the journey and closing the loop at either end. These tubes would be mounted on columns fifty to a hundred yards apart, and the pods inside would travel up to eight hundred miles per hour. Some of this Musk has hinted at before; he now adds that pods could ferry cars as well as people. ‘You just drive on, and the pod departs’, Musk told Bloomberg Businessweek in his first interview about the Hyperloop.
As mentioned in the above quote, if there’s an available pod, you’d be able to hop in or drive your car onto it. The concept seems like how a roller coaster works: line up, file into an open seat, buckle up and hold on.
Musk’s PDF states that capsules would each carry up to 28 passengers at a time, departing “on average every two minutes” or “up to every thirty seconds during peak-usage hours.” The alternative system that could carry cars would fit three “full-size automobiles” inside each capsule.
Musk told Businessweek: “You could have about seventy pods between Los Angeles and San Francisco that leave every thirty seconds. It’s like getting a ride on Space Mountain at Disneyland.”
So how would the Hyperloop actually work? Musk goes into great detail about it in the 57-page PDF, if you’re looking for the most technical explanation. But, according to Businessweek’s piece, the pods would be mounted atop thin skis and would move along inside the steel tubes while under low pressure, propelled forward by magnets and an initial electromagnetic pulse. The skis would have holes in them, through which air would be pumped, creating a levitation effect.
A physics professor at UCLA told Businessweek that similar systems already exist for use with real-world roller coasters, but that Musk “has separated the air cushion and the linear induction drive, and that seems new.”
As for safety, Musk’s PDF says: “The system is immune to wind, ice, fog, and rain. The propulsion system is integrated into the tube and can only accelerate the capsule to speeds that are safe in each section. With human-control error and unpredictable weather removed from the system, very few safety concerns remain.” About four pages of Musk’s 57-page PDF are devoted to possible safety concerns, including passenger emergencies, power outages, capsule depressurization, stranded capsules, tube integrity, earthquakes, and more.
At upwards of eight hundred miles an hour, the Hyperloop would theoretically have to be a straight shot between Los Angeles and San Francisco. How would you build it? Underground? Above ground? Through people’s backyards?
In his PDF, Musk says “the majority of the route will follow I-5 and the tube will be constructed in the median”, but concedes that it would have to follow a somewhat straighter path:

In order to avoid bend radii that would lead to uncomfortable passenger inertial accelerations and hence limit velocity, it is necessary to optimize the route. This can be achieved by deviating from the current highway system, earth removal, constructing pylons to achieve elevation change or tunneling.

It’s hard to turn at eight hundred miles per hour, in other words.
California’s seventy-billion-dollar proposal for a high-speed train system left Musk “disappointed”, as he mentions in his blog post, adding: “How could it be that the home of Silicon Valley and JPL— doing incredible things like indexing all the world’s knowledge and putting rovers on Mars— would build a bullet train that is both one of the most expensive per mile and one of the slowest in the world?”
According to Businessweek, “Musk figures the Hyperloop could be built for six billion dollars with people-only pods, or ten billion for the larger pods capable of holding people and cars. All together, his alternative would be four times as fast as California’s proposed train, at one-tenth the cost. Tickets, Musk says, would be ‘much cheaper’ than a plane ride.”
In the PDF, Musk writes: “Transporting seven million people each way, and amortizing the cost of six billion dollars over twenty years, gives a ticket price of twenty dollars for a one-way trip for the passenger version of Hyperloop.”
Just a minor detail here, but someone has to step up and build the Hyperloop, which means raising a bunch of money, getting California to okay a big double-barreled tube to be built along I-5 between San Francisco and Los Angeles, and a whole list of other details. Musk may have pitched the Hyperloop concept, but he has no intent to actually do anything with it right now; during a Tesla earnings call last week, Musk said, “I don’t have any plans to execute, because I must remain focused on SpaceX and Tesla.”

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