FW: TC Sparks and Arcs (Was - High Voltage Snubber caps

["John H. Couture" <couturejh-at-worldnet.att-dot-net> (by way of Terry Fritz <twftesla-at-uswest-dot-net>)]

Revised


Jim -

It is my understanding that the best man made vacuum on earth still has
millions of atoms in the chamber compared to outer space. This may make
sparks possible on earth depending on the amount of man made vacuum.
However, in space with the two isolated and energized terminals a distance
apart a spark would be impossible at any voltage because of the better
vacuum. Is this correct? I read somewhere there is only about one hydrogen
atom per cubic meter in the space between the stars. Not enough for sparks.

I agree that arcs would be possible in space and this is one of the
important differences between sparks and arcs. I think of sparks as a high
voltage phenomena and arcs as a low voltage phonomena. In other words the
initiation of the spark requires voltage while the arc requires current.

What do you mean by "it would be formed by being "drawn". What is being
drawn to form the spark?

John H. Couture

-----------------------------------

-----Original Message-----
From: Tesla list [mailto:tesla-at-pupman-dot-com]
Sent: Saturday, August 05, 2000 10:01 AM
To: tesla-at-pupman-dot-com
Subject: Re: TC Sparks and Arcs (Was - High Voltage Snubber caps


Original poster: "Jim Lux" <jimlux-at-jpl.nasa.gov>


> Original poster: "John H. Couture" <couturejh-at-worldnet.att-dot-net>
>
>
> Christopher, All -
>
> Are arcs and sparks possible in space beyond the earth's atmosphere? Can
a
> Tesla coil be operated in space if attached to the outside or inside of
the
> space shuttle?
>
> John Couture


Yes, however arcs & sparks in a vacuum are somewhat different than those in
a gas.  Typically it would be formed by being "drawn" (since a vacuum is a
very good insulator, in general), and the arc is actually supported by
metal ions from the electrodes. It quenches fairly quickly (i.e. the vacuum
circuit breaker) because it is hard to maintain enough ions to carry the
arc current as the arc gets longer.

A bigger problem for spacecraft is discharges across the surface.  Just by
travelling through the earth's magnetic field, the spacecraft gets charged
(move a conductor in a magnetic field and it causes a current.. i.e. how a
generator works...) The current charges up the capacitance of the various
components until it arcs.

A tesla coil would be interesting... I think it would discharge as a
surface discharge along the secondary.  I don't think you'd get streamers.
I've seen some high power transmitter and feedhorn testing in a vacuum
chamber at work, and you do get some discharge, but it's more diffuse.

Another issue is that while space is pretty empty, there ARE
micrometeoroids and other particles from the sun, etc.  When these hit you,
a small cloud of ionized gas is formed, which WILL arc over.  During meteor
showers (i.e. the Leonids last November) many higher power transmitters on
spacecraft are shut down so that there aren't any HV breakdowns due to
this.

It's unlikely, but if I ever get the chance, I'll try and run a TC inside
the 48" chamber on the antenna range...

BTW, if you were running your coil on Mars, you'd have the ideal situation.
 The atmospheric pressure on Mars (around 5 torr)  is such that the
breakdown voltage is about at the minimum....