I don't know where he got his stats, but the energy per passenger for a train cannot be right. CSX advertises daily they can move a ton of freight 400 miles for a dollar. A person weighs much less than a ton. Granted there are additional expenses to make a human comfortable, but these are relatively low fixed costs --you know like a chair.
Hyperloop
911–920 of 983 posts
Re: Hyperloop
#912Earlier quoted context omitted.
Well that's the point of a trade study: look at the cost/benefit of different gasses. Obviously one of the costs would be the increased engineering um...pressure put on the capsule design. Your gut feeling is probably right, though, at least for this length of trip. The increased cost of a different tube gas probably won't outweigh the benefits of arriving 5-10 minutes earlier. Now if there were a cross-continent Hyp…
http://www.phy.mtu.edu/~suits/SpeedofSoundOther.html The only ones I see that are significantly higher than nitrogen/oxygen are methane, hydrogen, and helium. Helium is mondo-expensive. It's not cheap even in welding-tank quantities, much less in the amounts you'd need here. Hydrogen is flammable and/or explosive (depending on mixture) and is a huge pain in the butt to keep confined (so is helium). Methane is cheap (…
Neon -> 2,090mph
Krypton -> 2505mph
Xenon -> 2,438mph
http://www.wolframalpha.com/input/?i=speed+of+sound+in+neon
http://www.wolframalpha.com/input/?i=speed+of+sound+in+krypt...
http://www.wolframalpha.com/input/?i=speed+of+sound+in+xenon
But even Neon (which is more abundant in the atmosphere than Helium) would cost ridiculous amounts of money to use.
Re: Hyperloop
#913Earlier quoted context omitted.
Mach value is lower for lower pressure, about 250 m/s for hyperloop proposal
Wolfram Alpha disagrees. It says: Mach(20 C, 1 atm): 343.051 m/s Mach(20 C, 0.1 atm): 343.182 m/s Not much higher, but definitely not lower. http://www.wolframalpha.com/input/?i=speed+of+sound+in+dry+a... Unfortunately, it refuses to show Mach(20 C, 0.001 atm), since the lowest supported pressure is 0.098 atm.
You are right, my bad with the low pressure speed of sound . Anyway the high transonic flow isn't a piece of cake as well.
Re: Hyperloop
#914Earlier quoted context omitted.
If they turn off the compressor there's a giant air cushion in front of them and the capsule no longer has air bearings. It probably lands on wheels and can then engage the breaks. A small capsule has low inertia as well. Most likely safer than a train.
Unfortunately the passengers inside still have high inertia. It doesn't matter if the capsule stops without damage if all the people inside are crushed by G-forces.
This is covered in some detail in the proposal. The capsules will be able to stop in the event of an emergency without hitting capsules in front or crushing passengers.
Re: Hyperloop
#915Earlier quoted context omitted.
> Cost is probably off by an order of magnitude, if not more. Why? Unions and other groups. Building anything in this country costs massively more (and takes significantly longer) than one could imagine because of our unions are not business symbiotic. The goal of union leadership is to extract as much as they can out of the businesses they infect, even if this means their demise. Musk is in the car industry, one of…
> Musk is in the car industry, one of the hardest hurt by unions and their ilk, so I would find it hard to believe that he didn't take that into account. That is irrelevant. He did not go into Tesla honoring the contracts that were put into place by GM, Ford, Chrysler and others. Those companies actually have tens of thousands of very well paid workers sitting around --literally-- all day doing nothing due to union c…
I don't know much about unions, I admit. But, I offer these this counterpoint:
The proposal is to use elevated tube on pylons. The pylons are likely to be of a regular design, probably made with steel molds. The amount of skilled labor to build them is likely to be much less than building overpasses.
Musk has said that the tubes would be built in 30m segments in a factory, and welded in place. Given Musk's experience with robot assembly at Tesla (watch http://kottke.org/13/07/how-the-tesla-model-s-is-made), my guess is that much of the construction of the tubes, and the rebar mesh for the pylons will be automated.
Making stuff in your factory as much as possible means you can automate more. It doesn't eliminate the labor, but it does reduce it a long way.
Re: Hyperloop
#916Earlier quoted context omitted.
> I would image the tubes will be joined with automated friction stir welding or something similiar, but that will still require a fair amount of post weld machining which has its own pitfalls The document mentions standard orbital seam wlelding, plus specialized machining equipment that travels along the tube to smooth out the gliding surface. The capsules are only 60% the diameter of the tube, or 36% it's area (68/…
> it doesn't seem to require tight tolerances for operation Well, it's true that the top and sides of the tube don't get too close to the capsule, so those parts seem relatively low-tolerance, as you say. But the load-bearing skis ride on an air bearing of 0.5mm to 1.3mm (see page 20), moving at over 1000km/h. As rossjudson notes, the skis are on mechanical suspension, to smooth out shocks to the riders, but it's not…
You could just build the tubes bending upwards slightly, so that the sag will pull them straight.
Re: Hyperloop
#917Earlier quoted context omitted.
But this comparison is wrong and meaningless. Certainly no one would build a high-speed, dense train network across, say, Nevada. But building one across the coastal part of California? Or across the NE United States? Why yes, that does make sense, and why yes, it is warranted by the densities in those areas. The fact that the U.S. also owns Alaska doesn't really matter. No one is arguing Alaska needs a high-speed ra…
I can believe that's a good plan for the US NE corridor... which already has usable (but improvable) Amtrak. The California coastal cities (and connecting areas) are still pretty sparse, comparatively. And the marquee High Speed Rail project takes a big inland detour to the smaller interior cities, for political reasons. If ever finished, that will hurt its price/time attractiveness compared to flying.
Even in the Northeast, Amtrak's improvement plans are incredibly wasteful:
http://pedestrianobservations.wordpress.com/2012/07/10/north...
Re: Hyperloop
#918Earlier quoted context omitted.
> it doesn't seem to require tight tolerances for operation Well, it's true that the top and sides of the tube don't get too close to the capsule, so those parts seem relatively low-tolerance, as you say. But the load-bearing skis ride on an air bearing of 0.5mm to 1.3mm (see page 20), moving at over 1000km/h. As rossjudson notes, the skis are on mechanical suspension, to smooth out shocks to the riders, but it's not…
You could just build the tubes bending upwards slightly, so that the sag will pull them straight.
Bridges and overpasses are already build that way.
Re: Hyperloop
#919High Speed Rail is still better:
High Speed Rail between downtown LA and downtown SF:
2 hours, 28 minutes
Hyperloop trip between downtown LA and downtown SF:
1 hour from LA to Sylmar via Metrolink
20 minute transfer
35 minutes to Dublin
20 minute transfer
1 hour 10 minutes from Dublin to SF via BART
Total: 3 hours 25 minutes
The project also doesn't even attempt to price the connection into LA or SF. That's where the high costs are.
Amusingly enough, the California HSR budget for the Central Valley is under $10 billion. Ie, in the same ball-park as this proposal. The reason the HSR project is going to cost $60 billion is because it has to face an uncomfortable truth; actually getting to LA and SF is expensive. Very expensive.
Is Elon Musk's s mega-announcement really just a last-ditch attempt to sabotage the California High Speed Rail (HSR) project, rather than a serious proposal to revolution travel? Something smells very fishy.
The motive is clearly there.
Re: Hyperloop
#920This is very serious first proposal. As a professional mechanical engineer I have worked on high quality steel tubes (nuclear submarines) before. The immediate thing that sticks out to me in this proposal are the tight mechanical tolerances that have to be maintained. Talking about tens of thousandths of an inch tolerances on a 10' diameter tube is not to be dismissed lightly. That is going to be tough to maintain -…
Thanks for writing! I can also imagine that when there's one very long tube there's going to be a lot of the length change with the temperature, ideally one wouldn't want to have any hard joints at all to allow the individual pieces to extend and shrink. One hundreds of miles long welded tube does sound potentially problematic.
The biggest problem seems to be that Musk's costs don't include most of the costs actually included in High Speed Rail proposal that allow you to actually travel between SF and LA and not SF minus bay (they omitted that cost) and Sylmar (where you've still got over an hour to go on the Antelope Valley Metrolink Line to reach the LA city):
http://stopandmove.blogspot.fr/2013/08/hyperloop-proposal-ba...
It seems that the proposal is actully much less serious than on the first glance:
Amusingly enough, the California HSR budget for the Central Valley is under $10 billion. Ie, in the same ball-park as this proposal. The reason the HSR project is going to cost $60 billion is because it has to face an uncomfortable truth; actually getting to LA and SF is expensive. Very expensive.
Moreover, would you like to be sitting in the tube on the chair from which you can't even stand up for a half an hour without the chance to do anything but remain sitting, not getting any help the next half hour on the occasion when you get sick? Would you take your kid there? Your parent?