BIOMED@CZHETH5A.BITNET (10/29/87)
Everybody talks about these 'warm superconductors'. A Nobel prize was given to the inventors, and the magazines are full of phrases like 'changing the world...'. Room temperature superconductors are expected for the near future. HOW will they change the world ? Power distribution: Zero resistance allows ultra high currents at low voltages. Can power lines go underground, because insulation is not a problem anymore ? How about the magnetic field ? Forces on ferromagnetic objects ? Cardiac pacemakers ? Compasses ? What happens, if a line breaks ? sqr(I)*L must be very high -> huge sparks at the breakpoint ? Power storage: Can high energy coils be built ? What energy per volume/weigth is possible, compared to batteries or gasoline ? The support structure for these coils will be under heavy mechanical stress. Is this the limiting factor ? Or is the loss of superconductivity at high magnetic field strength ? What if a coils breaks ? Huge bang ? Poisonous emissions ? Computers: Is the impact on computers that big ? I thought, the limiting factors today are the propagation speed of signals, and the stray reactances of the elements. Switching speed of transistors won't change, neither will inductance and capacitance of connecting lines. Or will they ? Comments are invited. Tom ANNA Zuerich, Switzerland. BIOMED@CZHETH5A (Bitnet)
rkn@ORNL-MSR.ARPA (Roger E. Stoller 576-7886) (10/30/87)
The relatively near-term 'life-changing' potential of these materials is probably very limited. Their use in electronic devices (an area I know little about) is the one that seems most practical. Their ability to be used in an application is limited by the massive engineering problem of moving 10-100's of thousands of miles of transmission lines underground and > reliably < keeping them cooled. Probably even more significant is the problem of fabricating the necesary wire. The so-called 123-superconductor is a ceramic and as such has very little ductility. Wire cannot be drawn in the conventional manner. A few tricks have been employed to make 'wires' in the laboratory to prove it could be done, but these techniques do not lend themselves to economic, large-scale application. These new materials are of significant scientific interest, and the longer range implications of their discovery are not necesarily clear - but the life-changing business is largely hyperbole. --------------------------------------------------------- Roger Stoller, rkn@ornl-msr.arpa, (615) 576-7886 Oak Ridge National Laboratory, Oak Ridge, TN. 37831-6376 ---------------------------------------------------------
haas@utah-gr.UUCP (Walt Haas) (10/30/87)
In article <8710291320.AA08591@bu-cs.BU.EDU>, BIOMED@CZHETH5A.BITNET writes: > ...Room temperature superconductors are expected > for the near future. > > HOW will they change the world ? Assuming the price is right and other problems can be solved, they may make solar energy the most economic source of electricity, at least in this part of the world. We've got lots of sunlight, and the technology for turning it into electricity has improved tremendously, but unfortunately there's currently no reasonable way to store it. Room temperature superconductors could solve this problem by simply circulating a current in a loop. ----------------* Cheers -- Walt ARPA: haas@cs.utah.edu uucp: ...utah-cs!haas DISCLAIMER: If my boss knew I was using his computer to spread opinions like this around the net, he'd probably unplug my ter`_{~~~
fiddler%concertina@Sun.COM (Steve Hix) (11/02/87)
In article <8710291320.AA08591@bu-cs.BU.EDU>, BIOMED@CZHETH5A.BITNET writes: > > Computers: > Is the impact on computers that big ? I thought, the limiting factors > today are the propagation speed of signals, and the stray reactances of > the elements. Switching speed of transistors won't change, neither will > inductance and capacitance of connecting lines. Or will they ? If you've got room-temperature (whatever *that* means) superconductors, there's no reason why you shouldn't be able to implements at least some of the switching components as something faster, such as josephson junctions. (Aren't the transistors in current devices used as fast switches, mostly?) Inductance and capacitance should change somewhat in response to device scale (but how much?). Since there are no resistance heating effects, you should be able to get much higher device densities (pack 'em closer and cut down on propagation delays) than currently possible. Faster (and eventually cheaper, maybe) devices result. Except for improvements in current drain and solving cooling problems, I doubt if exactly dublicating current design exactly in warm superconductors is going to be very useful. At least, compared to gains from implementing new types of devices, as well. (On the other hand, I'm just a software type, what do I know?) seh
fiddler%concertina@Sun.COM (Steve Hix) (11/02/87)
In article <8710301312.AA26625@ORNL-MSR.ARPA>, rkn@ORNL-MSR.ARPA (Roger E. Stoller 576-7886) writes: > The relatively near-term 'life-changing' potential of these materials > is probably very limited. It may a little early to tell yet. > Their use in electronic devices (an area I > know little about) is the one that seems most practical. Their ability > to be used in an application is limited by the massive engineering > problem of moving 10-100's of thousands of miles of transmission lines > underground and > reliably < keeping them cooled. This would probably be the case if transmission lines never needed to be replaced, repaired, upgraded, or new ones installed. If the new technology provides lower costs, better performance, reliability, easier acces for repair,...it will eventually probably be used. This, of course, supposes that the new technology can be developed and does provide one or more of the desired characteristics. Power companies work with fairly small (financial) margins...they'd not be too likely to turn down ways to improve their (and their stockholders) cash flow. > Probably even more > significant is the problem of fabricating the necesary wire. The > so-called 123-superconductor is a ceramic and as such has very little > ductility. Wire cannot be drawn in the conventional manner. A few > tricks have been employed to make 'wires' in the laboratory to prove > it could be done, but these techniques do not lend themselves to > economic, large-scale application. The materials currently discovered obviously don't fit the bill of something required for making wire, or handling huge magnetic fluxes, and...but aluminum wasn't exactly an ideal material 75-100 years ago. The cap on the Washington Monument was close to being as expensive as gold when it was put in place, but it wouldn't be now. (Aluminum is used for high-voltage transmission lines because it's cheaper than the better-conducting copper for equivalent line. Also lighter.) The first aircraft uses of aluminum (by people such as Dornier) were somewhat unsatisfactory, since early examples of Dural tended to either exfoliate or turn into this interesting, but not very useful, white powder. Such problems have pretty much been worked out. > These new materials are of > significant scientific interest, and the longer range implications > of their discovery are not necesarily clear - but the life-changing > business is largely hyperbole. You might be right...but, as you might have guessed, I don't think so. It's at least too early to tell yet. seh
hollombe@ttidca.TTI.COM (The Polymath) (11/02/87)
In article <8710291320.AA08591@bu-cs.BU.EDU> BIOMED@CZHETH5A.BITNET writes: >Everybody talks about these 'warm superconductors'. ... >HOW will they change the world ? >Is the impact on computers that big ? I thought, the limiting factors >today are the propagation speed of signals, and the stray reactances of >the elements. Switching speed of transistors won't change, neither will >inductance and capacitance of connecting lines. ... One of the limiting factors is heat dissipation. This limits how closely you can pack elements on a chip, which, in turn, limits signal propagation rates, switching delays, etc. Warm superconductors would allow much higher chip densities with accompanying increases in speed and complexity. Then there's the prospect of warm Josephson Junction technology, pocket Crays running off nine-volt batteries or solar cells, etc. ... The mind boggles. -- The Polymath (aka: Jerry Hollombe, hollombe@TTI.COM) Illegitimati Nil Citicorp(+)TTI Carborundum 3100 Ocean Park Blvd. (213) 452-9191, x2483 Santa Monica, CA 90405 {csun|philabs|psivax|trwrb}!ttidca!hollombe
ras@blade.UUCP (R.A. Schnitzler) (11/02/87)
Posting-Front-End: GNU Emacs 18.41.4 of Fri May 22 1987 on blade (berkeley-unix) Can anyone answer this question about the potential impact of room-temperature superconductors: If I built a semiconductor with superconducting paths (assume we figured out how to fabricate such things), would the resulting chip be hard to EMP (ElectroMagnetic Pulse)? That is, if the conductors within the chip were capable of effectively neutralizing any applied E field without undergoing heating due to the currents generated, what remaining threat is there from the large and sudden E fields associated with EMP? So, do I misunderstand something about EMP or superconductivity, or would this solve the (problem?) of building "hard" electronics? Ray Schnitzler Bell Communications Research bellcore!schnitz
garry@batcomputer.tn.cornell.edu (Garry Wiegand) (11/05/87)
(Cross-posted to rec.railroad) In article <8710291320.AA08591@bu-cs.BU.EDU> BIOMED@CZHETH5A.BITNET writes: >Everybody talks about these 'warm superconductors'. ... > >HOW will they change the world ? The most intriguing idea I've heard so far is to apply them to cheap magnetic levitation for trains. I'd guess the trains would travel significantly faster, use less fuel, and be exceedingly smooth and quieter-riding. The fuel is probably not significant, but could the other things give trains a shot at a comeback? I'd *love* to have an alternative to airplanes! Does anyone have technical knowledge? (I admit I would *not* love to have trains travelling at 400 mph past my house.) garry wiegand (garry@oak.cadif.cornell.edu - ARPA) (garry@crnlthry - BITNET)
neanders@phoenix.Princeton.EDU (Nels Anderson) (11/06/87)
In connection with high-temperature superconductors, garry@oak.cadif.cornell.edu writes in article <2824@batcomputer.tn.cornell.edu>: >The most intriguing idea I've heard so far is to apply them to cheap magnetic >levitation for trains. > >Does anyone have technical knowledge? Well, I have a little. Just a bit of the physics. I don't know anything about the engineering problems. According to an article in the IEEE Spectrum about three years ago, there are two types of magnetic levitation: electromagnetic and electrodynamic. In the electromagnetic system both the train and the track contain electromagnets. I believe the train's magnets are actually below the track, in a monorail-type arrangement. The magnets are oriented so as to attract each other, with the result that the train is pulled up. A control system is required to maintain the proper separation between the two sets of magnets, reducing the field if they come to close and increasing it if they get too far apart. Superconducting electromagnets could be used to eliminate resistive losses. Electrodynamic suspension is somewhat more elegant. It is based on the principle that a changing magnetic field will tend to induce a current in a conductor (copper, aluminum or a superconductor, for example). The induced current will flow in such a way as to create a magnetic field counter to the original field. If, for example, the changing magnetic field is caused by a magnet moving over the surface of the conductor, the induced currents in the conductor will repel the magnet in the vertical direction while attracting it horizontally. So the magnet is levitated and at the same time held near the center of the conductor. The catch here is that in normal conductors the induced currents die out rapidly. Constant motion is required to maintain the induced magnetic field. In a superconductor, however, the currents continue to flow indefinitely. Thus, if you send a magnet skimming over a block of aluminum at sufficiently high speed, the magnet will be levitated. If it slows down, however, the levitation will disappear. If you do the same thing with a superconductor, you find that the levitation persists even when the magnet isn't moving. A New York Times article on superconductors a few months ago showed a magnet suspended over a superconductor (or it may have been a superconductor suspended over a magnet -- the principal is the same). Without superconducting technology, an electrodynamically suspended train would contain an ordinary electromagnet and might ride over an aluminum track. (The track just has to be a good conductor and must not be ferromagnetic. It would start out on wheels. After reaching sufficient speed it would lift off the track. The New York Times article mentioned the possibility of using superconducting technology for the electromagnet. If superconductors were really cheap, the track could be superconducting as well. Then the train would float as soon as its magnets were turned on -- there would be no need to get up to speed. Superconducting track would also save energy, since the induced currents in nonsuperconducting track will tend to dissipate. The energy they dissipate has to come from somewhere, and I believe it shows up as a retarding force on the train. This would be quite substantial; the induced currents holding up a fast-moving train would be comparable to currents in the train's own magnets. Magnetic trains have been demonstrated by the British, Germans and, of course, the Japanese. As I recall from the IEEE article, the British system was electromagnetic. I don't know about the other two, but I believe that either or both of the German and Japanese experiments rely on conventional cold (liquid helium) superconductors. Nothing has been said yet about propulsion, as opposed to levitation. I presume that it is done by magnetic repulsion or attraction between electromagnets in the track and the train. I could go on at greater length about these things, but I suspect that everybody is bored already. Unfortunately I know only about the physical principals involved and nothing about the practical engineering problems. (Besides, my thesis advisor would dispute my claim to understanding ANY physical principals.) neanders@phoenix.princeton.edu neanders@phoenix.UUCP 6070106@pucc.bitnet
rvk@houdi.UUCP (R.KLINE) (11/06/87)
one benefit of magnetic levitation would probably be significantly lower roadbed wear. the primary function of "tracks" would be to correct lateral excursions. fuel savings might be significant because the major source of friction would now be wind drag. -r. kline
Niffleknob_Slaw@SFU.MAILNET (11/06/87)
Seems to me that warm super-conductors should make it easy (possible) to
build mass-drivers for slinging raw materials around the solar system
i.e: tossing space-station raw materials into orbit cheaply rather than
ferrying them up in shuttles at tremendous cost. Should also provide a
whole new order of cyclotron-like toys for the particle-physicists to play
with.dan@WILMA.BBN.COM (11/10/87)
I doubt that maglevs would make high-speed trains much more fuel-efficient; wind resistance, rather than wheel friction, is already the major energy consumer for high-speed rail operation. Dan Franklin
dmc@videovax.Tek.COM (Donald M. Craig) (11/10/87)
Once upon a time the Ontario government had (maybe they still do) a `Transportation Research Centre' in Kingston, Ontario. They had a maglev track and a train that ran around on it, using technology licensed from a German company (Krauss-Maffei ?). It seemed to work fine, in the summer. But when the winter blizzards howled off the Saint Lawrence River the track was buried under ice and snow, and all the lovely hovering clearances disappeared. They might still have the train, but they never bought another. There's a lot of sophistication in old train technology. When the Canadian National Railways introduced a United Technologies turbine powered (jet fuel yet) `Turbo' train on the Toronto - Montreal run in the early seventies, it took ten years of re-engineering before the things would run reliably during the winter. I remember on several occasions having to transfer to the diesel `Rapido' when the `Turbo' failed in the thick of a blizzard. Don Craig Tektronix Television Systems
robertj@yale-zoo-suned..arpa (Rob Jellinghaus) (11/16/87)
One aspect of the new superconductors that has not been touched on yet
is their applicability to electric motors. With current technology,
electric cars are not practical, because the motors are too heavy and
too inefficient, as are the batteries.
Warm superconductors could solve both of these problems. We could
create motors half the size and many times more powerful than the
electric motors of today. The batteries could also become more
efficient by orders of magnitude. This could get us out of our current
reliance on petrochemicals, and greatly reduce humanity's destruction
of the biosphere. Not to mention you never need go to the gas station
again; just plug in your car overnight!
Of course, this leaves out questions of intense electromagnetic fields
inside the car, ability to quickly accelerate, etc. But GE recently
created a solar-powered car that crossed Australia at an average speed
of over 40 mph (if memory serves). The thing only drove during the
daylight hours, but that's still an impressive feat. And that was with
non-superconductor technology. If that can be done now, imagine what
will be done when the supercoductors come along!
Rob Jellinghaus | "Lemme graze in your veldt,
jellinghaus@yale.edu.UUCP | Lemme trample your albino,
ROBERTJ@{yalecs,yalevm}.BITNET | Lemme nibble on your buds,
!..!ihnp4!hsi!yale!jellinghaus | I'm your... Love Rhino" -- Bloom Countydjw@beta.UUCP (David Wade, Computer Confuser Group, Chaotic Section, Administrator of illogical "Do Whiles".) (11/22/87)
In article <18946@yale-celray.yale.UUCP> robertj@yale.UUCP writes: > Not to mention you never need go to the gas station >again; just plug in your car overnight! > >Rob Jellinghaus And your house will burn down as the MEGAWATTS come swiftly into the noload battery...