Author Topic: The Hyperloop: BUSTED  (Read 78930 times)

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Offline nctnico

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Re: The Hyperloop: BUSTED
« Reply #375 on: June 08, 2019, 06:24:04 pm »
Spain and France are full of high speed trains.
Agreed. The French hold the speed record for the fastest train. Both Maglevs and regular trains suffer from the same problem: air friction. At some point it isn't going to be (financially) efficient to run trains at high speed and that is where the hyperloop concept comes in. And you don't need a complete vacuum. The energy consumption goes down linear with lowering the air pressure. Half the pressure means a 50% reduction in the energy lost due to friction (I'll leave it up to the reader to look up the formulas for energy loss due to friction versus air pressure).
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Offline ebastler

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Re: The Hyperloop: BUSTED
« Reply #376 on: June 08, 2019, 06:47:57 pm »
Spain and France are full of high speed trains.

Sure, as well as Italy, Germany, some lines in the UK and Belgium, ...
https://en.wikipedia.org/wiki/High-speed_rail_in_Europe

My point was that the Japanese Shinkansen was the first, by a fair margin to my knowledge.
 

Offline apis

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Re: The Hyperloop: BUSTED
« Reply #377 on: June 09, 2019, 12:03:01 pm »
Japan's L0 Series maglev holds the record with 603 km/h (on a test track), and the Shanghai maglev is the fastest in operation with a maximum normal operation speed of 431 km/h. Transrapid helped build the shanghai one, but it's only east Asia that's investing in maglev.

Half the pressure means a 50% reduction in the energy lost due to friction (I'll leave it up to the reader to look up the formulas for energy loss due to friction versus air pressure).
Not valid in a tube, the capsules will just push the air in front of it. That is why, in the concept art, the hyperloop capsules had large fans on the front that should funnel the air past the capsule.



The fan was probably also supposed to supply high pressure air for the air bearings.
« Last Edit: June 09, 2019, 02:20:34 pm by apis »
 

Offline soldar

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Re: The Hyperloop: BUSTED
« Reply #378 on: June 09, 2019, 02:19:34 pm »
Spain's high speed train system is a prestige project which makes no economic sense whatsoever.  The waste and corruption in grand projects like this are a shame in a country where money could be and should be employed more productively.
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Offline nctnico

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Re: The Hyperloop: BUSTED
« Reply #379 on: June 09, 2019, 02:22:33 pm »
Half the pressure means a 50% reduction in the energy lost due to friction (I'll leave it up to the reader to look up the formulas for energy loss due to friction versus air pressure).
Not valid in a tube, the capsules will just push the air in front of it.
That is just a technical detail which can be mitigated in several ways. The fact a lower air density reduces the amount of energy needed still stands.
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Offline apis

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Re: The Hyperloop: BUSTED
« Reply #380 on: June 09, 2019, 02:33:51 pm »
Half the pressure means a 50% reduction in the energy lost due to friction (I'll leave it up to the reader to look up the formulas for energy loss due to friction versus air pressure).
Not valid in a tube, the capsules will just push the air in front of it.
That is just a technical detail which can be mitigated in several ways. The fact a lower air density reduces the amount of energy needed still stands.
If you have two identical tubes with different pressure then a train in the evacuated tube will use less energy. But you were comparing open air to a tube which isn't a valid comparison.
 

Offline apis

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Re: The Hyperloop: BUSTED
« Reply #381 on: June 09, 2019, 02:46:07 pm »
Swedish politicians consider high speed rail every now and then but every local politician of every little municipality, no matter how tiny the population, demand that the train stop in their village or else they will not let the tracks cross their land. And if it's gonna make a stop every few km it's not going to be high speed. In the Schengen area it might make sense with maglev tracks between the largest cities. :-\
 

Offline technix

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Re: The Hyperloop: BUSTED
« Reply #382 on: June 18, 2019, 03:06:44 am »
Swedish politicians consider high speed rail every now and then but every local politician of every little municipality, no matter how tiny the population, demand that the train stop in their village or else they will not let the tracks cross their land. And if it's gonna make a stop every few km it's not going to be high speed. In the Schengen area it might make sense with maglev tracks between the largest cities. :-\
Here in China we have a similar situation. CR handles this by designing the stations to be passable at speed, so most of the faster trains just speed by the minor stations without even slowing down. It is a little bit scary to see a train pass by me at 350kph when standing on the platform...
 
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Offline soldar

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Re: The Hyperloop: BUSTED
« Reply #383 on: June 18, 2019, 10:09:14 am »
A couple years ago we took a train from Xi'an to Linfen on our way to visit the Hukou waterfalls. The distance from Xi'an to Linfen is about 350 Km so not really huge. We were told that there were not any "bullet trains" but there were "high speed" trains which were slower. The train was doing about 240 Km/hr which is pretty good. Immaculately clean and everything well organized and running smoothly, like a well oiled machine.  There is a yellow line on the platform and passengers are to stand behind it and well away from the edge. If you even dare put your toe over the line a pretty attendant will immediately correct you. Not surprising if trains may pass at speed without stopping.  China is a country where cleanliness is not a priority but I have not seen trains, stations, airports, etc. as clean and tidy in any other country.

I have seen projects of high speed trains which could load and unload passengers without stopping. I suppose it could be as simple as releasing the last carriage and speeding up a separate carriage and catching up with the train. A high speed train that has to make six ten minute stops adds over an hour to the schedule.
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Offline cyrusdreams

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Re: The Hyperloop: BUSTED
« Reply #384 on: August 22, 2019, 08:47:25 am »
I only found out yesterday that Elon didn't need to dig to the original old patent of this impractical idea.
Of all countries, in 1992, Switzerland proposed the "Swissmetro" system which has the exact same features as the the Hyperloop: vacuum tubes, maglev, highspeed, promise of energy efficiency.
Look up the Wikipedia article, there is even an official feasibility-study conducted (sorry, German only). Funny enough, all involved research parties were quite favorable, with the small footnote somewhere that the vacuum technology needs further investigation regarding power consumption and sealing of the system  :palm:

It was stupid a hundred years ago, it is stupid today, and it will still be stupid in a hundred years!
 

Offline EEVblog

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Re: The Hyperloop: BUSTED
« Reply #385 on: August 22, 2019, 08:48:56 am »
It was stupid a hundred years ago, it is stupid today, and it will still be stupid in a hundred years!

Don't stop more investment money...
 

Offline EEVblog

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Re: The Hyperloop: BUSTED
« Reply #386 on: August 22, 2019, 08:49:56 am »
A couple years ago we took a train from Xi'an to Linfen on our way to visit the Hukou waterfalls. The distance from Xi'an to Linfen is about 350 Km so not really huge. We were told that there were not any "bullet trains" but there were "high speed" trains which were slower. The train was doing about 240 Km/hr which is pretty good.

I've been on the Shanghai Maglev at 430kmh andi t's pretty awesome. Shame it doesn't go anywhere really useful.
 

Offline Brutte

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Re: The Hyperloop: BUSTED
« Reply #387 on: August 22, 2019, 09:30:57 am »
Of all countries, in 1992, Switzerland proposed the "Swissmetro" system
The economy of a transportation systems includes the factor that is "a value of time for a passenger". It is not surprising that Concorde traveled mainly between London/Paris and NY as there the factor gave Concorde an advantage over all other competing means of transportation (for some pa$$engers).
If you would like the same to happen with vacuum trains then this might happen only in some circumstances. It has to be in a place with high income and difficult transportation network. Switzerland and Alps fits. Germany and autobahns does not.

Quote
It was stupid a hundred years ago, it is stupid today, and it will still be stupid in a hundred years!

We need faster horses, not some automobiles.
 

Offline technix

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Re: The Hyperloop: BUSTED
« Reply #388 on: August 22, 2019, 12:11:51 pm »
I've been on the Shanghai Maglev at 430kmh andi t's pretty awesome. Shame it doesn't go anywhere really useful.
It would have went to Hangzhou should it not be some internal political strife during and after Chen Liangyu's tenancy as the mayor and Liu Zhijun's tenancy as Minister of Railways. The control center has enough coverage built into it, and there is preallocated space for a maglev station in Shanghai Hongqiao Transportation Hub.

There was even a debate on how Beijing-Shanghai HSR should be built - railways or maglev, and in early years the maglev solution was actually preferred since it is fundamentally faster.
« Last Edit: August 22, 2019, 12:14:25 pm by technix »
 
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Offline EEVblog

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Re: The Hyperloop: BUSTED
« Reply #389 on: August 22, 2019, 01:19:06 pm »
There was even a debate on how Beijing-Shanghai HSR should be built - railways or maglev, and in early years the maglev solution was actually preferred since it is fundamentally faster.

I got the impression that it's a much better technology in most respects, especially the elevated tracks, it just seems to be an energy requirement thing.
 

Offline EEVblog

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Re: The Hyperloop: BUSTED
« Reply #390 on: August 22, 2019, 01:22:13 pm »
If you would like the same to happen with vacuum trains then this might happen only in some circumstances.

It won't happen at all. It's just a fundamentally stupid idea from a practical engineering perspective.
 

Offline technix

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Re: The Hyperloop: BUSTED
« Reply #391 on: August 22, 2019, 01:34:42 pm »
I got the impression that it's a much better technology in most respects, especially the elevated tracks, it just seems to be an energy requirement thing.
Well the current high speed rail solution eventually won because of its compatibility with the existing railway infrastructure in China. Rescuing a stuck maglev train is a lot more difficult than rescuing a stuck railway train too. And the compatibility with existing infrastructure allows traditional locomotives being used as rescue engines on HSR.

Current China HSR system also make extensive use of elevated tracks too, with 4 out of 5 longest bridges in the world being part of mainland China's HSR network (and the remaining one on Taiwan's THSR.)
 

Online coppice

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Re: The Hyperloop: BUSTED
« Reply #392 on: August 22, 2019, 01:55:46 pm »
There was even a debate on how Beijing-Shanghai HSR should be built - railways or maglev, and in early years the maglev solution was actually preferred since it is fundamentally faster.

I got the impression that it's a much better technology in most respects, especially the elevated tracks, it just seems to be an energy requirement thing.
The big thing with maglev is the need for extremely rigid track. Trying to stabilise a train on a flexible track has defeated engineers so far. Making the track really rigid, rather than just strong enough to support the load, means the maglev in Shanghai uses an enormous amount of concrete. I don't think there is any particular issue with the track being elevated, but if they had made it at ground level it would have needed just as much piling, and just as thick a concrete bed to achieve the required rigidity.

Most people who think maglev should be low loss compared to a train seem to think of a train like a car. However, steel wheels have very low losses. As a kid we used to push lines of freight carriages around the local sidings at night. With persistence, even 3 or 4 small boys could get an enormous mass moving quite fast, because the rolling resistance is so low. If you look at the massive long distance freight trains in America, they don't go all that fast, but they are able to sustain the movement of kilometres of carriages with just the pull on one traction unit.
 

Offline boffin

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Re: The Hyperloop: BUSTED
« Reply #393 on: August 22, 2019, 04:11:52 pm »
The incremental speed from 300kmph to 400 isn't really going to save you that much in total time, once you factor in start/stop.  It would have to be a pretty significant distance before it was enough difference

What's the longest non-stop high-speed rail journey?  (The Ave Madrid-Barcelona have a few non-stops @ 625km /2h45m it's damn damn impressive; but most journeys make a couple of stops)

Plus, you can use high speed rails for lower (but still fast) speed stuff as well; such as freight hauling.

Sadly, I live in North America, where the car rules supreme, and people are too short-sighted to see rail really work well.  Once you take a 300kmph rail journey, you really wonder why the whole world doesn't do it.
 

Offline technix

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Re: The Hyperloop: BUSTED
« Reply #394 on: August 23, 2019, 03:00:40 am »
The incremental speed from 300kmph to 400 isn't really going to save you that much in total time, once you factor in start/stop.  It would have to be a pretty significant distance before it was enough difference

What's the longest non-stop high-speed rail journey?  (The Ave Madrid-Barcelona have a few non-stops @ 625km /2h45m it's damn damn impressive; but most journeys make a couple of stops)

Plus, you can use high speed rails for lower (but still fast) speed stuff as well; such as freight hauling.

Sadly, I live in North America, where the car rules supreme, and people are too short-sighted to see rail really work well.  Once you take a 300kmph rail journey, you really wonder why the whole world doesn't do it.
On Beijing-Shanghai HSR, there is a 617km/1h59min non-stop ride between Nanjing South and Jinan West, on the Shanghai Hongqiao to Beijing South train G2. The whole journey is 1318km/4h28min with those two stops.
 

Offline EEVblog

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Re: The Hyperloop: BUSTED
« Reply #395 on: August 23, 2019, 03:11:27 am »
On Beijing-Shanghai HSR, there is a 617km/1h59min non-stop ride between Nanjing South and Jinan West, on the Shanghai Hongqiao to Beijing South train G2. The whole journey is 1318km/4h28min with those two stops.

It's only 900km or so from Sydney to Melbourne. If the train could take 4 hours I'd certainly take it. Current train is about 11 hours.
 

Offline vk6zgo

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Re: The Hyperloop: BUSTED
« Reply #396 on: August 23, 2019, 08:56:27 am »
On Beijing-Shanghai HSR, there is a 617km/1h59min non-stop ride between Nanjing South and Jinan West, on the Shanghai Hongqiao to Beijing South train G2. The whole journey is 1318km/4h28min with those two stops.

It's only 900km or so from Sydney to Melbourne. If the train could take 4 hours I'd certainly take it. Current train is about 11 hours.


Over on Whirlpool  there was a discussion about shorter distance High Speed Trains.

They quoted a time duration for a HST trip from central Melbourne to Geelong.

On looking up the distance between the two, & comparing it with a trip over a similar distance between central Perth & Mandurah, it turns out that the existing narrow gauge commuter train on that service does the equivalent trip in a shorter time than their projected HST.

The difference, of course, is both topography, & that the Geelong trip would go a roundabout route via various "legacy" stations, whereas the Mandurah train goes straight down the centre of the Freeway.
 

Offline nctnico

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Re: The Hyperloop: BUSTED
« Reply #397 on: August 23, 2019, 09:22:55 am »
That is the problem with high speed train connections. Add too many stations and the travel time will go up quickly. I see it here too. High speed train between Amsterdam and Brussels (IIRC). Some cities where it passed demanded it stopped there too. But it kinda defeats the purpose. High speed trains need to operate like airplanes which travel distances over 300km. Otherwise a car or regular trains are usually quicker.
There are small lies, big lies and then there is what is on the screen of your oscilloscope.
 

Online coppice

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Re: The Hyperloop: BUSTED
« Reply #398 on: August 23, 2019, 11:05:34 am »
The difference, of course, is both topography, & that the Geelong trip would go a roundabout route via various "legacy" stations, whereas the Mandurah train goes straight down the centre of the Freeway.
A high speed train taking the scenic route seems more a basis for a comedy sketch than a civil engineering project.
 
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Offline technix

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Re: The Hyperloop: BUSTED
« Reply #399 on: August 23, 2019, 01:18:36 pm »
That is the problem with high speed train connections. Add too many stations and the travel time will go up quickly. I see it here too. High speed train between Amsterdam and Brussels (IIRC). Some cities where it passed demanded it stopped there too. But it kinda defeats the purpose. High speed trains need to operate like airplanes which travel distances over 300km. Otherwise a car or regular trains are usually quicker.
China have a similar problem too, but there is a solution: HSR stations that can be passed at speed. When a CRH train passes a station, it just speeds through at 350-380kph. The running lines never have a platform next to it, except at major stations where all trains must stop at anyway. China Railways also engineered high speed switches that can tolerate 400-450kph straight and 250kph side for use in those passable stations.

I was once on a platform waiting for another train when a train speeds through at 350kph on the second line from the platform. It is loud and a bit scary to be honest.
 


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