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Enclosed tube maglev system tested in China

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Re: Enclosed tube maglev system tested in China

#11

Post by dojomouse »

dnautics wrote: post #9
mcintyre1994 wrote: post #2

Can any physicists compare this briefly to hyperloop? The prototype tube has curves but would this have to go in a very straight line similar to hyperloop? Does it have the same safety issues in terms of being a closed pipe? - obviously that prototype with open air seats isn't going to carry anyone 1000mph+.

I don't think open air seats are good when you've got a low atmospheric pressure, either. It looks like the prototype is a mock-down at a lower scale. The principal advantage of hyperloop is that it takes the atmosphere (which is a liability for maglevs) and turns it into an asset,- by collecting it at the front and redirecting it below as a mode of levitation. This means the tracks can be unpowered. I'm not sure if…

The atmosphere isn't a liability for Maglevs, you could make hyperloop with maglev tech and it'd still work fine.

The tracks don't need to be powered for most Maglev concepts; superconducting maglev doesn't use powered track. Superconducting maglev is also energetically extremely cheap from an operating perspective - it's arguably energetically expensive during construction because you need a shitload of permanent magnet material (the entire track surface is coated with it). The superconductors are the cheap part from a system perspective. Electromagnetic suspension - like with shanghai maglev - also doesn't need a powered track, the relatively small amount of power required can be supplied by onboard batteries and periodically refreshed. Inductrack can be combined with magnetic propulsion, it's just not a form of magnetic propulsion in itself. There's no obstacle to integrating a separate propulsion stage into the track (as is proposed in the inductrack based container movement system proposed for... LA?)

Re: Enclosed tube maglev system tested in China

#12

Post by darkmighty »

melling wrote: post #6
danmaz74 wrote: post #4

Earlier quoted context omitted.

I would be curious to know what is the advantage of using maglev technology if you only reach speeds of 120 km/h. "Firstly, there is no friction, and little noise or vibration; secondly, it eliminates the risk of derailment; and lastly, it is an eco-friendly method of transportation without emissions" looks like nothing special to me.

I'm not really sure how to answer this. You're kind of asking me to explain the value of safety and noise. I guess most people really put a high price on safety. Accidents do happen on subways: http://www.newsday.com/news/new-york/f-train-derails-in-nyc-... Subways, and rail in general, can be quite noisy. Paris uses rubber tires on their subway, for example. http://en.wikipedia.org/wiki/Paris_M%C3%A9tro In Silicon V…

Aren't noise barriers more cost effective solutions?

http://en.wikipedia.org/wiki/Noise_barrier

Re: Enclosed tube maglev system tested in China

#13

Post by Anechoic »

danmaz74 wrote: post #7
melling wrote: post #6

Earlier quoted context omitted.

I'm not really sure how to answer this. You're kind of asking me to explain the value of safety and noise. I guess most people really put a high price on safety. Accidents do happen on subways: http://www.newsday.com/news/new-york/f-train-derails-in-nyc-... Subways, and rail in general, can be quite noisy. Paris uses rubber tires on their subway, for example. http://en.wikipedia.org/wiki/Paris_M%C3%A9tro In Silicon V…

Honestly, the safety argument looks pretty moot to me - monorails don't derail either. For the noise, that's cool, but I'm under the impression that a high speed maglev will be quite noisy too.

high speed maglev will be quite noisy too.

At [0] http://ntl.bts.gov/lib/22000/22500/22570/fra0213.pdf

Re: Enclosed tube maglev system tested in China

#14

Post by cattypist »

dnautics wrote: post #9
mcintyre1994 wrote: post #2

Can any physicists compare this briefly to hyperloop? The prototype tube has curves but would this have to go in a very straight line similar to hyperloop? Does it have the same safety issues in terms of being a closed pipe? - obviously that prototype with open air seats isn't going to carry anyone 1000mph+.

I don't think open air seats are good when you've got a low atmospheric pressure, either. It looks like the prototype is a mock-down at a lower scale. The principal advantage of hyperloop is that it takes the atmosphere (which is a liability for maglevs) and turns it into an asset,- by collecting it at the front and redirecting it below as a mode of levitation. This means the tracks can be unpowered. I'm not sure if…

The story also says "Zigang has a tube that lowers air pressure in the running environment to 10 times less than normal." (This probably makes little sense to someone who's good at physics of gases--reducing by 100% or 1x is the lowest you can go with that.)

In general, I guess this story has about the level of quality that one should expect of a science & engineering story sourced from the _Daily Mail_.

Re: Enclosed tube maglev system tested in China

#15

Post by mcintyre1994 »

cattypist wrote: post #14
dnautics wrote: post #9

Earlier quoted context omitted.

I don't think open air seats are good when you've got a low atmospheric pressure, either. It looks like the prototype is a mock-down at a lower scale. The principal advantage of hyperloop is that it takes the atmosphere (which is a liability for maglevs) and turns it into an asset,- by collecting it at the front and redirecting it below as a mode of levitation. This means the tracks can be unpowered. I'm not sure if…

The story also says "Zigang has a tube that lowers air pressure in the running environment to 10 times less than normal." (This probably makes little sense to someone who's good at physics of gases--reducing by 100% or 1x is the lowest you can go with that.) In general, I guess this story has about the level of quality that one should expect of a science & engineering story sourced from the _Daily Mail_.

Hmm I didn't read it quite like that - I read it as reducing it to 10%, a reduction of 10 times from normal 100%.

Re: Enclosed tube maglev system tested in China

#16

Post by nkozyra »

darkmighty wrote: post #12
melling wrote: post #6

Earlier quoted context omitted.

I'm not really sure how to answer this. You're kind of asking me to explain the value of safety and noise. I guess most people really put a high price on safety. Accidents do happen on subways: http://www.newsday.com/news/new-york/f-train-derails-in-nyc-... Subways, and rail in general, can be quite noisy. Paris uses rubber tires on their subway, for example. http://en.wikipedia.org/wiki/Paris_M%C3%A9tro In Silicon V…

Aren't noise barriers more cost effective solutions? http://en.wikipedia.org/wiki/Noise_barrier

Depends on how you quantify "cost." For a lot of people aesthetics and livable appeal factor into that.

Re: Enclosed tube maglev system tested in China

#17

Post by pistle »

How does one pressurize the cabin in a serious vacuum tube? How long will it take and will there be special requirements to adjust pressures for travelers in such devices?

Is this not essentially equivalent to going for a ride in the space station for us out of shape schlubs?

Re: Enclosed tube maglev system tested in China

#18

Post by headcanon »

pistle wrote: post #17

How does one pressurize the cabin in a serious vacuum tube? How long will it take and will there be special requirements to adjust pressures for travelers in such devices? Is this not essentially equivalent to going for a ride in the space station for us out of shape schlubs?

From the article, it doesn't appear to be a full vacuum tube, just much lower pressure, which airplanes have been protecting their passengers against for years.

Also, the reason astronauts need to be so physically fit is not because the environment outside their ships is a vacuum, its because they have to be able to handle the immense g-forces of launch and reentry, as well as be able to operate in micro-gravity, which wouldnt apply here.

Re: Enclosed tube maglev system tested in China

#19

Post by dnautics »

dojomouse wrote: post #11
dnautics wrote: post #9

Earlier quoted context omitted.

I don't think open air seats are good when you've got a low atmospheric pressure, either. It looks like the prototype is a mock-down at a lower scale. The principal advantage of hyperloop is that it takes the atmosphere (which is a liability for maglevs) and turns it into an asset,- by collecting it at the front and redirecting it below as a mode of levitation. This means the tracks can be unpowered. I'm not sure if…

The atmosphere isn't a liability for Maglevs, you could make hyperloop with maglev tech and it'd still work fine. The tracks don't need to be powered for most Maglev concepts; superconducting maglev doesn't use powered track. Superconducting maglev is also energetically extremely cheap from an operating perspective - it's arguably energetically expensive during construction because you need a shitload of permanent ma…

Atmospheric drag absolutely is a liability... That's the whole point of an evacuated maglev.. To make an artificial atmosphere with lower drag. Note how the mockdown chassis cross section is small relative to the tube... That's also a drag limitation; and note how hyper loop has a nearly full tube cross section.

Re: Enclosed tube maglev system tested in China

#20

Post by dojomouse »

dnautics wrote: post #19
dojomouse wrote: post #11

Earlier quoted context omitted.

The atmosphere isn't a liability for Maglevs, you could make hyperloop with maglev tech and it'd still work fine. The tracks don't need to be powered for most Maglev concepts; superconducting maglev doesn't use powered track. Superconducting maglev is also energetically extremely cheap from an operating perspective - it's arguably energetically expensive during construction because you need a shitload of permanent ma…

Atmospheric drag absolutely is a liability... That's the whole point of an evacuated maglev.. To make an artificial atmosphere with lower drag. Note how the mockdown chassis cross section is small relative to the tube... That's also a drag limitation; and note how hyper loop has a nearly full tube cross section.

Sorry, I didn't word that very clearly - yes it's a liability, but it's a liability that's fairly independent of the levitation mechanism. I think it's more clear to say "That's the whole point of evacuated tube transport, to make an artificial...". Whether you use wheels or maglev or air bearings is a separate issue. Hyperloop doesn't turn the atmospheric drag into an asset - it just uses a particular method of overcoming the large liability. Because of how it overcomes it, it might be able to get away with a higher blockage ratio, but to say that with any real confidence you need to specify the vacuum level in the high-vac example you're comparing it to. And then do a bunch of compressible flow math that I've not yet seen for a high-vac ETT. This paper (http://jmt.swjtu.edu.cn/EN/abstract/abstract8587.shtml) looks at the incompressible flow case... but that's kind of missing the point I think.
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