Criticism Mounts of the Hyperloop
In recent days several writers and analysts have taken a closer look at Elon Musk’s proposed Hyperloop and found serious flaws in the proposal. One of these critics is Matt Johnson of Greater Greater Washington who argues the math doesn’t add up:
The Hyperloop pods will travel at up to 760 miles per hour, just under the speed of sound, with pods traveling about 30 seconds apart in the tube. They will have a maximum deceleration of 0.5 gs, which is equivalent to 10.9 mph per second. At that rate of braking, it will take a pod 68.4 seconds to come to a full stop.
That’s a pretty significant issue because safe vehicle operation means never getting closer to the vehicle ahead than the distance it will take you to stop. If pod A were to experience a catastrophic air-skid failure, crash into the tube wall, and disintegrate, pod B, 30 seconds back, would not be able to stop short of the wreckage. In fact, pod C would also likely hit the wreckage of pods A and B.
That means that the minimum separation between pods is probably closer to 80 seconds or more. Not a big deal. It still means 45 departures per hour. But that’s only 1,260 passengers per hour in capacity. That’s 10% of what the California High-Speed Rail can carry.
With a capacity of 1,260 passengers per tube, that means that the Hyperloop would need 10 tubes in each direction (not 1) to move the same number of passengers as the proposed high-speed line. And that would push the cost up by 10, which is actually more than the cost of the HSR.
Johnson also points out the Hyperloop proposal isn’t from downtown San Francisco to downtown Los Angeles – it’s from Oakland to Sylmar. That won’t serve the same market as HSR intends to serve, and while HSR plans to share tracks from Sylmar to Union Station, Musk has no provision for service to downtown LA.
Johnson also provides a good analysis of the idea of using an elevated guideway for the Hyperloop, pointing out the significant engineering challenges this would entail and the high costs that come with it. His analysis concludes that it’s very hard to see how the Hyperloop could be built for the absurdly low $6 billion cost that Musk proposes.
Alon Levy takes a look at the physics of the Hyperloop and concludes it’s a barf ride:
This is worse than sideways acceleration: track standards for vertical acceleration are tighter than for horizontal acceleration, about 0.5-0.67 m/s^2, one tenth to one seventh what Musk wants to subject his passengers to. It’s not transportation; it’s a barf ride.
Levy takes a look at the estimates for Hyperloop energy consumption and comes to a damning conclusion:
Indeed, a train with a thousand seats, 20 MW of power drawn, 60% seat occupancy, and a speed of 360 km/h can only ever expend 333 kJ per passenger-km while accelerating, and much less while cruising (acceleration at lower speed requires more energy per unit of distance, but cruising at lower speed expends only a fraction of the energy of full-power acceleration). Tesla’s train energy consumption numbers do not pass a sanity check, which suggests either reckless disregard for the research or fraud. I wouldn’t put either past Musk: the lack of references is consistent with the former, and the fact that Musk’s current primary endeavor is a car company is consistent with the latter.
And even the comedians are getting in on the act, with The Daily Show’s John Oliver mocking the Hyperloop:
Yet the tech geeks remain excited by the Hyperloop – because they can’t come to accept that high speed rail is itself a big leap forward, a cutting edge yet proven technology that moves a lot of people at speeds no land-based technology has yet been able to provide on a regular basis. Here’s Gizmodo making the case against bullet trains:
And yet the proposed high-speed rail line in California isn’t a big enough step forward by many accounts. It’s not using the fancy magnetic levitation technology being implemented in places like Japan and Germany, which will allow trains to fly down the tracks at over 300 mph. The trip from San Francisco to Los Angeles would take 2 hours and 38 minutes, an average speed of 164 miles-per-hour, which is pretty zippy compared to what we’ve had in the United States before, but not all that impressive by global standards. And as Musk points out, it’s not even really energy-efficient, when you consider the per-passenger energy expenditure.
Except the “fancy magnetic levitation technology” isn’t being implemented on a broad scale anywhere, including Japan and Germany. Maglev has never gotten beyond use on a few small short routes, in part because it is a huge technological leap forward that comes at an enormous cost. High speed trains that can break 200 mph are cutting edge and represent the innovative frontier of land-based transportation. Musk has done a good job convincing the media that he is the next step forward and trains are passé, but the vactrain that is the basis of Musk’s idea is itself a century old.
Much of the media coverage of the Hyperloop follows Musk’s own framing, which is basically that high speed rail sucks and that we should build something like the Hyperloop despite the fact that HSR is a proven technology and the Hyperloop isn’t.
There’s no good reason to pit these against each other. California HSR serves a hundred million more riders than the Hyperloop would, for a predictable cost with off-the-shelf technology. It’s about to begin construction and will do a huge amount of good for the state’s economy, energy independence, and carbon reduction efforts. The Hyperloop is also an idea worth exploring and perfecting. But it isn’t an alternative to or a replacement for high speed rail, and it should certainly not be treated as such.
Yet that is how the Hyperloop has been sold by Musk and reported by the media. That reveals not a fetish for new technology, but an anti-rail bias that is hard to understand or defend. As Amtrak’s record ridership shows, Americans and Californians in particular really like passenger trains and want more of them. Electrified trains reduce carbon emissions and provide a lot of people with a reliable, affordable, fast way to get where they want to go. Build more trains, of all kinds, should be a top national priority. I can dream that someday I will ride the Hyperloop between SF and LA. But I know for a fact that within the next 20 years I absolutely will ride the bullet train between SF and LA. That knowledge makes all the difference.