It's pretty much a dead end technology with such drawbacks (in addition to the classic maglev trouble of special tracks). Pierre
But that's part of the story: if the technology is so expensive you can't build 150 km of line, it's quite normal you leave the record to the guys who can... Otherwise, we could validate records for trains with a solid booster rocket up the %*$!&
Something much more technical: are you familiar with the catenary "wall of sound" problem ? I'd like to know why the trivial solution of a double catenary with different mechanical tensions is not applicable ? (I presume it is not applicable, otherwise all our bright polytechniciens at alsthom would certainly have jumped on it) Pierre
Don't write them off too fast: an extension of the Shanghai line to Hangzhou is still in the plans (for 2010), and that's 170 km, enough for a very nice record. (They achieved 501 km/h on the just 30 km long present line.)
Regarding the catenary critical speed, how do you imagine a double catenary with different mechanical tension? If you mean side-by-side, then both will have their own critical speeds, nothing solved. If you mean fastened to each other, that doesn't work, because the catenaries move in every direction: say if there is a temperature change, and one catenary lengthens more than the other, the tension will be transplanted. *Lunatic*, n. One whose delusions are out of fashion.
Does it simply break if the train keeps on accelerating (by any auxiliary mean other than the catenary under consideration) until it makes contact again definitively ahead of the wave ? Or can you "break" the wall like planes can beat sound just by having enough extra thrust at the right moment ? Pierre
It just snaps, AFAIK. When a plane goes supersonic, it still pushes a shock wave ahead of it (the "wall" becomes a cone), but the shock wave in a metal line would tear it, I surmise.
On a more general note, catenary is not cheap -- and two catenaries (each of which have to be sufficient for conducting maximum currents) would be double prize, not to mention the extra spanning work and the the extra wear on the pantographs. So I'd guess pushing the critical speed higher (stronger alloys, different material, more weights on the ends) is cheaper anyway. *Lunatic*, n. One whose delusions are out of fashion.
Could it be that a contact-less panto sucks the current by ionizing air a few centimeters away from the catenary ? You would need some tight feedback loop to keep it a the right distance (too close, it hits, too far, it looses conduction), but 200 m/s doesn't rule it out with some telemetry/radar continuously tracking the catenary.
Or may be the simple fact of having a 20 MW spark would displace the catenary and still cause a shockwave ? Pierre
By the way, speaking of catenary/pantrograph research, I know that both the Japanese and the Germans developed active pantographs, regulating for constant pressure on the catenary. I wonder where Alstom and SNCF are with that technology. *Lunatic*, n. One whose delusions are out of fashion.
There is a large ballast rock strip on either side of the railway, dunno if it's specially larger for high speed railways, but there must be burning metal shards falling on it all the time.
Actually, if the panto was contact-less and the spark was just like lightning, a canal of ionized air, it wouldn't expand past the area between catenary and panto and nothing would get chipped away to the ground. Pierre
