Dre comments on [LINK] Hyperloop officially announced — predictions, anyone? - Less Wrong

4 Post author: malcolmocean 12 August 2013 09:30PM

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Comment author: Dre 14 August 2013 05:54:14PM 8 points [-]

I thought this was an interesting critical take. Portions are certainly mind-killing, eg you can completely ignore everything he says about rich entrepreneurs, but overall it seemed sound. Especially the proving-too-much argument; the projections involve doing multiple revolutionary things, each of which would be a significant breakthroughs on its own. The fact that Musk isn't putting money into doing any of those suggests it would not be as easy/cheap as predicted (not just in a "add a factor of 5" way, but in a "the current predictions are meaningless" way).

Also, the fact he's proposing it for California seems strange. There are places with cheaper, flatter land where you could do a proof of concept before moving into a politically complicated, expensive, earthquake-prone state like California. I've seen Texas (Houston-Dallas-San Antonio) and Alberta (Edmonton-Calgary) proposed, both of which sound like much better locations.

Comment author: kalium 15 August 2013 02:17:08AM *  6 points [-]

Some points from the article you linked:

  • The cost estimates don't make much sense.

    Central Valley land is cheap; pylons are expensive, as can be readily seen by the costs of elevated highways and trains all over the world. The unit costs for viaducts on California HSR, without overhead and management fees, are already several times as high as Musk’s cost: as per PDF-page 15 of the cost overrun breakdown, unit costs for viaducts range from $50 million to $80 million per mile. Overheads and contingencies convert per-mile cost almost perfectly to per-km costs. And yet Musk thinks he can build more than 500 km of viaduct for $2.5 billion, as per PDF-page 28 of his proposal: a tenth the unit cost.

  • The proposed accelerations (and change in acceleration) would be likely to cause motion sickness in many passengers.

  • Capacity would be low, and the proposed headway of 30 seconds is unrealistic.

    The proposed headway is 30 seconds, for 3,360 passengers per direction per hour. A freeway lane can do better: about 2,000 vehicles, with an average intercity car occupancy of 2. HSR can do 12,000 passengers per direction per hour: 12 trains per hour is possible, and each train can easily fit 1,000 people (the Tokaido Shinkansen tops at 14 tph and 1,323 passengers per train).

  • Musk's values for HSR energy consumption are not accurate.

    However, one thing could not: the chart on PDF-page 9 showing that only the Hyperloop is energy-efficient. The chart has a train consuming nearly 900 megajoules per person for an LA-San Francisco trip, about as much as a car or a plane; this is about 1,300 kJ per passenger-km. This may be true of Amtrak’s diesel locomotives; but energy consumption for HSR in Spain is on average 73 Watt-hour (263 kJ) per passenger-km (see PDF-page 17 on a UIC paper on the subject of HSR carbon emissions), one fifth as much as Tesla claims.

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