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Re: Spark length dependence on air pressure.

Original poster: "Mike" <induction@xxxxxxxxxxx>

Robert,
I find that over a 6 feet path of plain air and an open circuit voltage of 1100 volts, with flat electrodes of diameter 22.5 inches, the ideal pressure range is ~100 to 200 Millitorr. 100 Mt is about 75 Km (Sprite area) That is about 246,000 feet. At this 1100 volts first a glow discharge then as the chamber is more ionized, it drifts across the glow discharge mode into the arc discharge mode. To protect the system from runaway currents, inductive ballast is adjusted. With a current in arc discharge mode of 4.25 amps across this 6 feet at 100 Millitorr, the voltage drop across both ends of the chamber is 185 volts.
While it is cool to say "Yes I am using air as a conductor for "high" current"" it is also clear that for a distance of 6 feet, I certainly could do better in a conductor that did not a 185 volt drop across it at only 4.25 amps. Yes it is true higher voltage
would drive the system into the "negative resistance" and greater current but it still remains a voltage driven, with lossy drop, operation. Anyway, anybody running an arc great distances would make so much radio noise, the hams of the world would find then and alter their gender.
So, besides getting that high, getting voltage up to that point, it is far more effective to run copper wires on the ground as we do now. Maybe for remote power delivery to some test aircraft, earth bound lasers and solar support would be better. I imagine up that high solar cells would really crank out power.
Mike
----- Original Message ----- From: "Tesla list" <tesla@xxxxxxxxxx>
To: <tesla@xxxxxxxxxx>
Sent: Tuesday, June 28, 2005 3:51 PM
Subject: Re: Spark length dependence on air pressure.


Original poster: Jim Lux <jimlux@xxxxxxxxxxxxx>

At 11:01 AM 6/28/2005, Tesla list wrote: 
Original poster: Robert Clark <bobbygc2001@xxxxxxxxx>

 Well, you don't need it to be the *easiest* altitude
to get breakdown, just some altitude where it is so
low you can get conduction over many kilometers.
 BTW, what is the pressure at which the lowest
breakdown voltage occurs? What is the altitude at
which this pressure is reached?


Roughly 100k ft or a bit higher, roughly 5-10 torr.
Called "critical pressure" in the spaceflight electronics business, not to be confused with "critical pressure" in respect of thermodynamics and phase changes.