Junior Ganymede
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Musk’s Hyperloop

August 13th, 2013 by John Mansfield

Dissatisfied with the price and worth of high-speed rail in California, Elon Musk turned some of his SpaceX and Tesla engineers loose on the idea of regional transport between Los Angeles and San Francisco. Their white paper describes a pair of seven-foot diameter steel tubes mounted on concrete pylons along Interstate 5. The tubes are pumped down to 100 Pascals, or, as Musk’s team prefers to call it, 1/6 the atmospheric pressure of Mars. Inside the tubes, 28-passenger vehicles riding on air bearings would run the 350-mile route in 35 minutes, 70% of the time at near-sonic 760 mph.

As a fluid dynamicist, I enjoy the centrality of airflow in the concept, and that part of the plan looks reasonable. The estimated construction cost for the tubes, pylons, and vacuum pumps is put at $4 billion. The whole system is $6 billion before operating costs.

Musk doesn’t have any personal plans for the concept beyond getting the idea out there (Washington Post article). I wonder what useful shorter routes could test the concept and show that it really can beat high-speed rail. Further, I wonder about its worth as an updating of the trolley lines that suburban developers put down a century ago. If a low-cost, 15-minute ride were available to travel the 120 miles from Hiko to downtown Las Vegas, and another for the 130 miles from Beatty, living on a desert spread and working in town would be a new kind of possible. Of course, that kind of thing is always a mix of welcome and otherwise. I hang on to an irrigation share in the Moapa Valley that I can’t stand the idea of parting with. The Moapa Valley is 60 miles from Las Vegas, and most people with jobs drive to Las Vegas. I worry that some year transplants to Nevada from places with two-hour commutes are going to discover the place.

Comments (4)
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August 13th, 2013 08:15:44
4 comments

Adam G.
August 13, 2013

Conceptually it looks sound but there’s obviously lots of development work that would have to happen to see if its really workable or not. I’m a little skeptical about the price points.

Given the capital costs, it probably doesn’t make sense at all for exurban developments, especially since the work patterns have been changing and not everyone works downtown these days. You have to have a really high ridership to make the numbers work. The kind of situation you’re talking about is where driverless cars will make a difference.


Bookslinger
August 13, 2013

I think it would be foolish to attempt to construct long distance air-tight vias in a seismicly unstable area.

Compensating for the normal daily and seasonal cycles of thermal expansion/contraction is a big enough challenge.


Adam G.
August 13, 2013

Books,
the initial draft proposal has the pylons being on earthquake footings.


Bookslinger
August 14, 2013

Adam, perhaps you missed my point. An earthquake is more than shaking and vibrating. Earthquakes also change the horizontal distance between given points on the earth surface. While each pylon may be able to remain standing and whole, the distance between them will change if there is sufficient tectonic movement along faults that are on or near the path.

Engineering for expansion and contraction (due to cycles of heat/cold, and due to geological movement) of construction projects (railroads, highways, bridges, buildings, oil/gas/water/sewer pipelines) is a serious and complicated thing. It’s hard enough when it does not have to be “liquid-tight” (buildings, bridges, highways), but rather hard (and difficult to maintain) when it has to not leak oil/gas/water.

All need to allow for flexion and expansion/contraction. The latter have to have flex-joints and expansion/contraction joints that are _leak-proof_ in addition to allowing movement. The seals of leak-proof types of moveable joints have a limited lifetime, and often have to be replaced due to geological movement.

Furthermore, oil/gas/water pipelines have isolated segments. They don’t go for hundreds of miles un-interrupted. There are inline pumping and storage stations which allow for the segments to be isolated if there is a catastrophic failure in one segment. Yet this speculated air tube seems to require an uninterrupted segment of several hundred miles.

Even when there is not a quake, there is slight movement every year across faults. A quarter inch crack in a highway doesn’t stop traffic, and can easily be repaired. But a quarter inch crack in a tube transporting 800 mph air and 800 mph containers is a much bigger deal.

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