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Re: Lightning Gun To Combat Terrorists - WHERE IS THE RETURN PATH???

Original poster: Jim Lux <jimlux@xxxxxxxxxxxxx>

At 02:33 PM 9/5/2005, Tesla list wrote: 
Original poster: Terry Fritz <vardin@xxxxxxxxxxxxxxxxxxxxxxx>

Hi Stork,

At 01:13 PM 9/5/2005, you wrote:

Radio waves only need an antenna long enough to create a potential difference in the presence of electromagnetic waves. They operate in free space such as on satellites and space craft. In a real way, EM waves tend to bring the ground path along with them ;-)

Oh, I get it, a traveling virtual ground. Is this virtual ground at the same potential as the real ground from where it was launched?

Nope... a propagating EM wave just has an Efield (and of course, the corresponding H field at right angles). You can put probes into the field and measure the voltage and/or extract some power from the travelling wave, which is what an antenna really is.


It is an isolated floating ground that could be any potential. I wonder if satellites in open space have any known net charge on them? Maybe Jim Lux would know that?

It's truly floating (in that it's not necessarily referred to some other "far away" point. I suppose you could, but you'd have to deal with the fact that you'd be measuring it at some "other time".

As far as charge on spacecraft, you bet they charge. It's a real problem, because the charge builds up unevenly, and if it arcs, bad things happen. For an example near and dear to my heart, the Japanese ADEOS II (aka Midori) satellite probably had charge accumulate on the thermal blankets, which weren't connected to the chassis. They sparked over to the power wires on the solar panels, and the full solar panel power was able to continue the arc, burning its way along the wires, killing the satellite, and with it an instrument that I helped build. (Some of this is speculation, since nobody was there to see it).

It's also an issue for the shuttle and ISS.

There are two charging effects: one from charged particles, the other because it's a conductor moving in a magnetic field.