On 4/11/16 8:57 PM, erwinrommel Helwig wrote:
Arcing is a much greater problem at high altitudes. D.C. Generator output is reduced at altitudes above 15,000 feet due to arcing. This is due to brush arcing.
A good rule of thumb is that the air density/pressure decreases by a factor of 2 for every 18,000 ft.
So at 18,000 ft, the air pressure is 380 torr, at 36,000 it's 190 torr, etc.And further, as a rule of thumb, the breakdown voltage goes linearly as the pressure. So a gap that holds off 15kV at sea level will only hold off 7500 volts at 18,000 ft.
This is down to a pressure around 2-10 torr, where the curve bottoms out, and the breakdown voltage starts increasing again as the gap has more and more of a vacuum.
Sent from my iPhoneOn Apr 12, 2016, at 5:04, "Jerry" <jerry@xxxxxxxxxx> wrote: I imagine the exact nature of the discharge depends on the electrode shape and other factors, but fersure the 'Or nothing' option is not the correct one. Aircraft electronic equipment that employ substantial voltages have a maximum altitude rating for that very reason. I remember some equipment from decades ago warning against operation above 50K feet. In any case, you should be able to find reference materials that have interesting tables. If you're going to record the experiment with a camera, consider putting a micro-ammeter in the circuit to document the increasing leakage current with altitude. Put a couple of back-to-back diodes across the meter to protect it when the electrodes flash over.On 04/11/2016 03:27 PM, Paul B. Thompson wrote: Recently I've gotten involved with a group of high altitude balloon hobbyists. We're always looking for interesting experiments to try in the stratosphere, and I thought of one with HV application. I'd like to run it by everyone here as a thought-experiment first. Air is a dielectric. Not a great one, but a sufficient air gap between two electrodes prevents arcing. (I may not be expressing this the best way, but you all know what I mean.) If you lower the air pressure greatly, would a high voltage spark leap across the same distance? I imagine something like a charged flash capacitor being lofted in a balloon. The poles of the cap are connected to electrodes separated by a gap sufficient to prevent discharge at normal air pressure. If the balloon lifts the apparatus to, say, 100,000 feet, will we see the apparatus arc over when the air is sufficiently attenuated? Or will we get a kind of corona glow? Or nothing? A camera would be pointed at the gap to film the result. Paul Thompson _______________________________________________ Tesla mailing list Tesla@xxxxxxxxxx http://www.pupman.com/mailman/listinfo/tesla-- Jerry Chamkis (Linux Desktop) jerry@xxxxxxxxxx "Non-locality is spooky action at -zero- distance." www.teslaphone.com/ote/TIME.mp3 www.kosmophone.com www.aerco.net Vow to vanquish the venal and virulent vermin vanguarding vice and vouchsafing the violently vicious and voracious violation of volition! (V For Vendetta) _______________________________________________ Tesla mailing list Tesla@xxxxxxxxxx http://www.pupman.com/mailman/listinfo/tesla_______________________________________________ Tesla mailing list Tesla@xxxxxxxxxx http://www.pupman.com/mailman/listinfo/tesla
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