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
