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By "high-temperature" superconductivity, physicists mean liquid nitrogen temperature, not room temperature. It's progress, but cheap maglev is still a ways off.

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>By "high-temperature" superconductivity, physicists mean liquid nitrogen temperature

...sure, but there are superconductors at a lot warmer temperatures than 77K.

mercury barium calcium copper oxide at 133 K (atmospheric pressure). http://adsabs.harvard.edu/abs/1993Natur.363...56S

Hydrogen Sulfide at 203K, under pressure:

http://physicsworld.com/cws/article/news/2015/aug/21/hydroge...

Liquid nitrogen is much easier and cheaper to work with than liquid helium (probably most US high schools see freeze and break a banana or similar experiments regularly; it costs very little).

IMO it would still be a major real world breakthrough when this is ready for engineering use. But while this research may be a big step to that goal, it does not yet move the problem from science to engineering.

I used to do a lot of cryogenics work during my PhD.

The statistic one of the professors often quoted was that "LN2 is cheaper than milk".

Although LN2 is cheaper and more abundant, it's also 20 times warmer than LHe. That matters a lot for applications.

To get an idea of ability to restrict thermal excitations, LN2 at 77K is only 4x 'colder' than room temperature. But LHe (4.2K) is 18x 'colder' than LN2, or 72x 'colder' than room temperature!

The 4x 'colder' here really threw me. Took me a minute to realize you meant 1/4 the temperature. Strikes me as an odd phrasing, like saying "airplanes fly 23x 'lower' than LEO".

It's odd but correct because temperature has a minimum.

We're just used to Celsius/Fahrenheit temperatures where you can't say that.

There is already a short (1 km long) high voltage, nitrogen cooled superconducting cable in use in Germany:

http://www.extremetech.com/extreme/182278-the-worlds-first-s...

Thanks: http://www.nexans.de/eservice/Germany-de_DE/fileLibrary/Down...

I'd say one of the more exciting possibilities is helium-free NMR & MRI.

The high temperature stuff is still very sensitive to strong changing magnetic fields, so I'm not holding my breath for MRI.

But don't ignore improvements in low temperature superconductors engineering:

https://dspace.mit.edu/openaccess-disseminate/1721.1/91644

...I also believe that GE is working on a MRI using liquid hydrogen as the cryogen.

> I also believe that GE is working on a MRI using liquid hydrogen as the cryogen.

What could possibly go wrong?

Not much. Liquid hydrogen could leak a little. Then it could burn a little. In the liquid form its 100's of degrees away from burning.

"This asphyxiant gas is expensive and dangerous if it leaks. What should we do?"

"Well... we could replace the asphyxiant with an explosive gas?"

"..."

It's pretty easy to make high-temperature (liquid nitrogen) super conductors already , I remember making this in undergraduate labs a few years ago:

https://en.wikipedia.org/wiki/High-temperature_superconducti...

The problem with them is that they are not ductile, and only super-conduct in 2 dimensions (along the planes of the material) and therefore it is difficult to do anything with them.

Isn't China building affordable low-speed maglevs? I believe the S1 Line in Beijing is almost finished.

https://en.wikipedia.org/wiki/Line_S1,_BCR

It travels at around 110kph (68mph).

That seems a bit odd. What's the advantage over an ordinary wheeled train at speeds < 600 km/h?

Well, I imagine that maglev is faster, quieter, and has better acceleration than a subway or light rail. You don't need to go 600 km/h across town.

Getting tens of thousands of people to their destinations 10 minutes quicker adds up.

Wheeled electric trains are already limited in their acceleration rates by passenger comfort, so we don't need superior acceleration or braking. Sound level is the only one advantage that really seems plausible.

Speed?

http://www.nyctransitforums.com/forums/topic/17313-subway-sy...

And for some reason, NYC subways aren't a very smooth ride. Are you sure maglevs wouldn't accelerate faster?

Also, I'd think a maglev from Manhattan to JFK would be preferable to a subway.

A new low-speed maglev started operation in Changsha last May.[1] This is China's first maglev built with Chinese technology. The Shanghai airport maglev uses the German Transrapid system.

Few countries can build a maglev. A US company tried and failed to build even a simple, slow maglev.[2]

[1] http://www.scmp.com/news/china/society/article/1941693/china... [2] http://ireport.cnn.com/docs/DOC-586439

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