

Enclosed tube maglev system tested in China - jyrki
http://phys.org/news/2014-05-enclosed-tube-maglev-capable-mph.html

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melling
While this is cool, it's probably decades away. People should note that low-
speed maglevs have arrived.

[http://www.globaltimes.cn/content/860672.shtml](http://www.globaltimes.cn/content/860672.shtml)

[http://english.cri.cn/6909/2014/05/16/2702s826842.htm](http://english.cri.cn/6909/2014/05/16/2702s826842.htm)

A few of these would be nice in NY or LA. JFK to Manhattan in 20 minutes.
Cross the width of Manhattan in 4 minutes.

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danmaz74
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.

~~~
melling
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-...](http://www.newsday.com/news/new-york/f-train-derails-in-nyc-subway-
officials-say-1.7898804)

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](http://en.wikipedia.org/wiki/Paris_M%C3%A9tro)

In Silicon Valley, one of the reasons people don't want HSR near their homes
is because of the noise:

[http://www.businessinsider.com/silicon-valley-high-speed-
rai...](http://www.businessinsider.com/silicon-valley-high-speed-rail-2011-4)

Ever hear the above ground train pass by in DUMBO in Brooklyn, NY?

Anyway, a super-smooth quite ride at a mile a minute certainly does seem like
an appealing way to get around a big city.

~~~
danmaz74
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.

~~~
Anechoic
_high speed maglev will be quite noisy too._

At <100mph, the TR08 is fairly quiet [0]. When I was en Elmsland for the noise
testing, it was common for the vehicle to sneak up on us when it was running
at lower speeds. At higher speeds, especially over 150 mph when aerodynamic
noise kicks in, it is very loud.

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

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mcintyre1994
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+.

~~~
dnautics
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 tracks are powered in the chinese
maglev, but the article said "superconducting" so that's energetically costly
either on the pod or on the tracks.

An interesting maglev alternative to superconduction is inductrack, which,
however, cannot be combined with magnetic propulsion -
[https://en.wikipedia.org/wiki/Inductrack](https://en.wikipedia.org/wiki/Inductrack)

~~~
dojomouse
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?)

~~~
dnautics
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.

~~~
dojomouse
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](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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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?

~~~
headcanon
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.

