Re: BIG plasma spheres

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Jan Florian Wagner by way of Terry Fritz <twftesla-at-uswest-dot-net>" <jwagner-at-cc.hut.fi>

Hi,

> >I've been asked about the feasibility of building a 4 foot(ish) diameter
> >hemisphere or spherical display.
> neat idea - I was thinking about  you might do this a while ago. One
> thought I had to make things simpler is to put the secondary inside,
> and the primary outside the envelope, to avoid the need to pass wires
> through a seal. 

Just my $0.02 here...

I remember there was some group of those -dot-org sites (www.lod-dot-org ?
www.thegeekgroup-dot-org) that had tested their larger scale TC with a gas
filled huge plastic balloon or ball at atmospheric pressure.

Maybe there are transparent travel-balloons (or whatever they're called,
those things you can hang under) or weather balloons?

You should be aware that it might get quite expensive - AFAIK Neon runs at
very roughly $1000 per 10l tank (200 bar), Helium $500 per 10l tank, Xenon
$1500 per 10l, yesterdays price estimates (I just happened to phone AGA
yesterday, same purpose as you, just much smaller scale globe). 

You can dry pumping a globe down to somewhere between 50 and 300 Torr (not
milliTorr), which reduces gas needed, but increases cost of the globe.
Also, globe material is an issue - plastic will leak in/out gases with
time. With rubber => larger or equal to atm. pressure required, more gas,
also leaks like hell. It won't be exactly cheap.


 - Jan