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Attack-Proof Power Line to be Installed Under NY
Podcaster writes "American Superconductor Corporation and Con Edison have announced a joint effort to develop and deploy a new system that utilizes high temperature superconductor power cable technology in Con Edison's grid in New York City. The project, called Project Hydra, will aim to establish 'Secure Super Grids' that can withstand extreme weather and terrorist attacks."
Don't want to RTFA? That's fine, this is /. after all. Here's a summary of the main points to get you started:
-P
Be my friend.
As a HAM, you should know the answer. Broadband over Powerlines only causes interference due to the frequencies in the power lines being the same as you might try to transmit at. In these, the frequency is going to be 60hz, the frequency of your electrical outlet. I highly doubt you are ever going to be transmiting at 60hz on purpose.
Fly me to the moon Let me sing among those stars Let me see what spring is like On jupiter and mars
Liquid nitrogen isn't that big a deal. Many businesses routinely handle the stuff. The key problems here are maintaining a supply of liquid nitrogen and the safety issues surrounding a cryogenic liquid that can displace oxygen when in gaseous form and which boils below the boiling point of oxygen. It can be dangerous, but not unusually so for an environment involving high voltage equipment.
Economy of New York
If it were a country, its GDP would be the 17th largest in the world. It makes a prime target for economic reasons, and major terrorist action in New York would have a significant impact on the rest of the nation.
This does sound like a grab for homeland security money, certainly; but it's not unreasonable, on the whole, to keep a special eye on New York when it comes to preventing terrorism.
"Surely it is conceivable to cool liquid nitrogen down a little below it's boiling point."
Well, yes, in theory you can do that. I haven't read up on my cryogenics, but the trick is to exchange heat efficiently in order to lower the temperature of the liquid nitrogen. One way to do that is to use an even colder medium and a heat exchanger, which is kind of futile, since the colder medium can be used directly. The other method is to use compressible phase-changing gases, such as found in refrigirators. At this moment I cannot think of a reason why that is impractical. Perhaps there is a lack of suitable elements/gases..
This website http://www.uigi.com/nitrogen.html, however, gives a very good reason:
"When liquid nitrogen is vaporized and warmed to ambient temperature, it absorbs a large quantity of heat. The combination of inertness and its intensely cold initial state makes liquid nitrogen an ideal coolant for certain applications such as food freezing."
So the energy/heat required for the phase change of nitrogen from liquid to gas is quite a respectable one, making operating with liquid nitrogen at that temperature (i.e. the b.p.) a preferable one.
I do know, however, that with special techniques, it is possible to cool liquid helium a little further towards the zero Kelvin point. This is used, for example, in MRI scanners to minimize the boiloff of helium. I believe they have now acheived zero (!) boiloff.
B.
Every experiment which ends in a big bang is a good experiment.
Magnetic levitation in superconductors occurs due to the Meissner-Ochsenfeld effect, which is slightly different than what the parent describes. The parent's memory may well not be faulty, however, as the Meissner effect is often erroneously explained in terms of perfect diamagnetism and Faraday's Law of Induction. While it is true that as a perfect conductor, a superconductor is also a perfect diamagnet, and can be expected to generate an opposing electromagnetic field in response to a changing magnetic flux through it, a superconductor also opposes a constant field.
This can be demonstrated by placing a magnet on top of a superconductor above its critical remperature, then cooling the superconductor below the critical temperature. When the superconductor hits the critical temperature, the applied field from the magnet will be expelled out to the London depth (about 50 nanometers in most superconductors), and the magnet will levitate. It's a subtle difference from the perfect diamagnetism explanation, but it was one of the key clues that led to the explanation of superconductivity as a phase transition and as a nonclassical process.
"FDA staff reviewers expressed concern about the number of patients who were left out of the study because they died."
He's talking about liquid oxygen. If you leave liquid nitrogen in contact with air, it'll gradually collect liquid oxygen as oxygen condenses in the liquid nitrogen.