6 ms·

>The Hyperloop pods will travel[...] about 30 seconds apart in the tube. They will have a maximum deceleration of 0.5 gs [...] it will take a pod 68.4 seconds t

by zeteo 13y ago

>The Hyperloop pods will travel[...] about 30 seconds apart in the tube. They will have a maximum deceleration of 0.5 gs [...] 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. [...] That means that the minimum separation between pods is probably closer to 80 seconds or more. Two flawed assumptions in here: 1. 0.5 g is the maximum deceleration under normal conditions (see p. 58 in Musk's PDF). Emergency braking would obviously be capable of more. The linear accelerators themselves are spec'd to be capable of 1g, and there's an onboard emergency braking system on top of that. 2. A vehicle that crashes doesn't stop immediately, but continues on its direction of motion due to inertia. That's why the two second rule is plenty safe on highways [1], even though expected vehicle stopping times are six seconds or more [2]. Furthermore, the article is basically an attack on maximum capacity, but that's not a real issue. The system is economically viable if it can get passengers from point A to point B at comfort and cost levels (including recouping investment) that compare favorably with other means of transportation; Musk cites $20 per ticket, which the article doesn't dispute Maximum capacity can always be expanded if the economics work otherwise. [1] http://en.wikipedia.org/wiki/Two-second_rule http://en.wikipedia.org/wiki/Two-second_rule [2] http://www.csgnetwork.com/stopdistinfo.html http://www.csgnetwork.com/stopdistinfo.html

ronaldx 13y ago
On point 2: if you get jammed in a tube you're going to stop in a much shorter distance than if you're freewheeling on a road.
tptacek 13y ago
Isn't that $20 estimate prima facie incredible? It's based on the capex costs of the system but not opex, right? It presumes that once you build the system, it runs itself for free.
- zeteo 13y ago
  It seems really low, but I don't really know what to dispute among p. 56 estimates. Energy comes from solar panels. It doesn't seem to factor in maintenance. Even if the cost turns out to be double and we factor in a 20% profit margin, it would still be much cheaper (and possibly faster) than a HSR ticket.
  - tptacek 13y ago
    Amtrak can't even cover it's operating costs with it's (much more expensive) ticket. Amtrak's operating expenses are dominated by headcount costs. Amtrak is obviously not a model of efficiency, but it's certainly a valid data point about the scale of operating costs we're talking about. The $20 ticket is a myth. The only way anyone pays $20 to ride this thing is if the taxpayers take up the other $140 of slack.
    - jbooth 13y ago
      For the record, last I heard, Amtrak is actually incredibly profitable in the northeast and almost profitable along the west coast. It's the losses from running the rest of the system that kill it.
    - zeteo 13y ago
      Amtrak has a very different business, operating and even physical model. Sure, they're both transportation, but unless there's detail in the specifics we might as well compare the Chinatown bus with renting a Cessna.
      - tptacek 13y ago
        Yeah, I shouldn't have made the crack about Amtrak not covering its budget; it too vividly drew a comparison between Amtrak's structural problems and the hypothetical problems of this project. The only point I was actually trying to make is the (I hope) uncontroversial one that operating expenses for a transit system are high.
    - dvanduzer 13y ago
      A ~30 minute trip does not require the conductors, attendants or kitchen staff of, say, the two day trip the California Zephyr takes. The overhead of those workers' wages would scale roughly with ridership. Amtrak ridership is up dramatically this year[0], but it is still 20x smaller than for domestic air travel[1]. They employ nearly 5000 people in mechanical and maintenance roles[2], which is a cost largely independent of ridership. You can argue the case that Musk's cost estimates are overly optimistic, but Amtrak's operating costs are largely relevant. [0] http://www.sacbee.com/2013/03/01/5227255/amtrak-ridership-up-55-percent.html http://www.sacbee.com/2013/03/01/5227255/amtrak-ridership-up... [1] http://www.transtats.bts.gov http://www.transtats.bts.gov [2] http://www.amtrak.com/ccurl/533/3/Amtrak-Mechanical-Services-201109.pdf http://www.amtrak.com/ccurl/533/3/Amtrak-Mechanical-Services...
- jfb 13y ago
  What I don't fully understand is how this is any better than conventional HSR. What are the advantages? Cost, but that remains to be seen. Absolute speed, which yes, but where are the time estimates from Hayward to the Transbay Terminal in SF, and from Sylmar to Union Station in LA? This whole thing reads to me as purest wind. EDIT: At least on a conventional train, I can ride from somewhere that's not at one of the endpoints to somewhere else that isn't; and, of course, I can go to the bathroom.
  - tptacek 13y ago
    It's interesting how, in terms of door-to-door transit time, the extreme speed of the Musk plan is a liability; it basically ensures the system can't connect city centers. I read a post last week that compared the situation to the Shinkansen, which was an expensive political show project until they figured out how to get it to population centers.
    - RyanZAG 13y ago
      The Shinkansen has transported more than 10 billion passengers. I'd love to have a few more expensive political show projects like that. If your point is they started off with areas they still needed to work out like connection to population centers, then I think you're on the wrong site: every startup we discuss pivots in one way or another to overcome challenges, that's an accepted part of developing something useful. If you don't try you're never going to get to a point when you can find a solution to problems you don't know exist yet. If there was a hyperloop between the edges of SF and LA, how many minutes do you think it would take before someone worked out how to get passengers the short distance from the station to the city center?
      - tptacek 13y ago
        You missed my point, which wasn't that Shinkansen was bad. It's like you read up to the first command and stopped. On your other point: how much incentive is there to get people from SF to Mountain View faster? HUGE incentive, is the answer to that question. What's the answer right now? 101 and 280, or a long slow train ride.
- dasmoth 13y ago
  What fraction of "conventional" public transport costs are labour? I think (if it gets built!) we'll see very few humans operating or maintaining the hyperloop.
  - tptacek 13y ago
    I think we'll see more. Among other things, the Hyperloop plans are predicated on TSA-style security at the endpoints. That doesn't happen on conventional trains; there's security, but it's nothing like airport security. It's never getting built, though. An insurmountable advantage of HSR is that it can serve population centers along its route, which makes ROW acquisition feasible. I don't think the car company has much to do with things (you can make an argument that a better HSR infrastructure would help Tesla, not hurt it, by reducing its customers need for the long-haul drives that are the weak point of electric cars), but I do think the Hyperloop is best understood as a political maneuver to complicate CA HSR.
anologwintermut 13y ago
Point 2 isn't necessarily correct when you factor in the effect of debris on bearings.

by zeteo 13y ago

ronaldx 13y ago

On point 2: if you get jammed in a tube you're going to stop in a much shorter distance than if you're freewheeling on a road.

tptacek 13y ago

Isn't that $20 estimate prima facie incredible? It's based on the capex costs of the system but not opex, right? It presumes that once you build the system, it runs itself for free.

zeteo 13y ago
It seems really low, but I don't really know what to dispute among p. 56 estimates. Energy comes from solar panels. It doesn't seem to factor in maintenance. Even if the cost turns out to be double and we factor in a 20% profit margin, it would still be much cheaper (and possibly faster) than a HSR ticket.
- tptacek 13y ago
  Amtrak can't even cover it's operating costs with it's (much more expensive) ticket. Amtrak's operating expenses are dominated by headcount costs. Amtrak is obviously not a model of efficiency, but it's certainly a valid data point about the scale of operating costs we're talking about. The $20 ticket is a myth. The only way anyone pays $20 to ride this thing is if the taxpayers take up the other $140 of slack.
  - jbooth 13y ago
    For the record, last I heard, Amtrak is actually incredibly profitable in the northeast and almost profitable along the west coast. It's the losses from running the rest of the system that kill it.
  - zeteo 13y ago
    Amtrak has a very different business, operating and even physical model. Sure, they're both transportation, but unless there's detail in the specifics we might as well compare the Chinatown bus with renting a Cessna.
    - tptacek 13y ago
      Yeah, I shouldn't have made the crack about Amtrak not covering its budget; it too vividly drew a comparison between Amtrak's structural problems and the hypothetical problems of this project. The only point I was actually trying to make is the (I hope) uncontroversial one that operating expenses for a transit system are high.
  - dvanduzer 13y ago
    A ~30 minute trip does not require the conductors, attendants or kitchen staff of, say, the two day trip the California Zephyr takes. The overhead of those workers' wages would scale roughly with ridership. Amtrak ridership is up dramatically this year[0], but it is still 20x smaller than for domestic air travel[1]. They employ nearly 5000 people in mechanical and maintenance roles[2], which is a cost largely independent of ridership. You can argue the case that Musk's cost estimates are overly optimistic, but Amtrak's operating costs are largely relevant. [0] http://www.sacbee.com/2013/03/01/5227255/amtrak-ridership-up-55-percent.html http://www.sacbee.com/2013/03/01/5227255/amtrak-ridership-up... [1] http://www.transtats.bts.gov http://www.transtats.bts.gov [2] http://www.amtrak.com/ccurl/533/3/Amtrak-Mechanical-Services-201109.pdf http://www.amtrak.com/ccurl/533/3/Amtrak-Mechanical-Services...
jfb 13y ago
What I don't fully understand is how this is any better than conventional HSR. What are the advantages? Cost, but that remains to be seen. Absolute speed, which yes, but where are the time estimates from Hayward to the Transbay Terminal in SF, and from Sylmar to Union Station in LA? This whole thing reads to me as purest wind. EDIT: At least on a conventional train, I can ride from somewhere that's not at one of the endpoints to somewhere else that isn't; and, of course, I can go to the bathroom.
- tptacek 13y ago
  It's interesting how, in terms of door-to-door transit time, the extreme speed of the Musk plan is a liability; it basically ensures the system can't connect city centers. I read a post last week that compared the situation to the Shinkansen, which was an expensive political show project until they figured out how to get it to population centers.
  - RyanZAG 13y ago
    The Shinkansen has transported more than 10 billion passengers. I'd love to have a few more expensive political show projects like that. If your point is they started off with areas they still needed to work out like connection to population centers, then I think you're on the wrong site: every startup we discuss pivots in one way or another to overcome challenges, that's an accepted part of developing something useful. If you don't try you're never going to get to a point when you can find a solution to problems you don't know exist yet. If there was a hyperloop between the edges of SF and LA, how many minutes do you think it would take before someone worked out how to get passengers the short distance from the station to the city center?
    - tptacek 13y ago
      You missed my point, which wasn't that Shinkansen was bad. It's like you read up to the first command and stopped. On your other point: how much incentive is there to get people from SF to Mountain View faster? HUGE incentive, is the answer to that question. What's the answer right now? 101 and 280, or a long slow train ride.
dasmoth 13y ago
What fraction of "conventional" public transport costs are labour? I think (if it gets built!) we'll see very few humans operating or maintaining the hyperloop.
- tptacek 13y ago
  I think we'll see more. Among other things, the Hyperloop plans are predicated on TSA-style security at the endpoints. That doesn't happen on conventional trains; there's security, but it's nothing like airport security. It's never getting built, though. An insurmountable advantage of HSR is that it can serve population centers along its route, which makes ROW acquisition feasible. I don't think the car company has much to do with things (you can make an argument that a better HSR infrastructure would help Tesla, not hurt it, by reducing its customers need for the long-haul drives that are the weak point of electric cars), but I do think the Hyperloop is best understood as a political maneuver to complicate CA HSR.

anologwintermut 13y ago

Point 2 isn't necessarily correct when you factor in the effect of debris on bearings.