>>9508662to my knowledge he never made that type of high altitute "full scale" instalation with ballons it was just a proposal, he mostly experimented with ""smaller"" lab apparatus, one he describes in the patent he put the terminals inside a sealed container-tube under a rarefied atmosphere to improve the conditions for the discharge to take place at lower voltages (2 to 4 MVolts):
>page4, parag.0 "The outer end of the secondary or high-tension coil A was connected to the ground, as illustrated, while the free end was led to a terminal placed in the rarefied airstratum through which the energy was to be transmitted, which was contained in an insulating-tube of a length of fifty feet or more (50 feet , 15 meters) , within which a barometric pressure varying from about one hundred and twenty to one hundred and fifty millimeters (120 to 150 mmHg, about 5 to 6 inHg of vacuum) was maintained by means of a mechanical suction-pump.">page4, parag.15: "an electromotive force from two to four million volts (2 to 4 MV) and more was obtainable at the terminals of the secondary coil A, the discharge passing freely through the attenuated air stratum maintained at the above barometric pressures"https://patentimages.storage.googleapis.com/62/90/92/45a5932052a940/US645576.pdfvery good video demostration: "Paschen's Law ( Curve )-Effect of a Vacuum on a High Voltage Arc"
https://www.youtube.com/watch?v=2yAFSTrCxBQthe graph basically means that the higher the vaccum the lower the voltage needed to start conduction (to start an arc) but only up to a point! a "hard vauum" is basically a insulator (BTW vacuum-tubes work on electron emission, a "hard vacuum" is desirable, you dont want arcs in a vacuum-tube!...)
