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Re: Spark length dependence on air pressure.



Original poster: Robert Clark <bobbygc2001@xxxxxxxxx>

--- Tesla list <tesla@xxxxxxxxxx> wrote:

> Original poster: Mddeming@xxxxxxx
>
> Original poster: Robert Clark
> <bobbygc2001@xxxxxxxxx>
>
>  >>>Snip
>
>    My idea would be to locate a Tesla coil high in
> the
> atmosphere such as by a high altitude balloon. The
> power for the TC would come from a power line
> attached
> to the balloon from the ground. Then the TC would
> shoot power to the launch craft from the balloon.
> Since they are high in the atmosphere the required
> voltage would be much less.
>    I still need to know though how long the sparks
> could
> be that would be created.
>
>  >>>snip
>
>     Bob Clark
>
> HI Bob,
>
>      You are encountering some of the same
> engineering problems that
> plagued Tesla a century ago. Tesla had concluded
> that high conductivity
> required an atmospheric pressure of 100-150
> mTorr.(see US Pat. 645,576)
> This requires an altitude of 10-15 miles, and the
> problem here is that any
> known metallic cable of any diameter will collapse
> of its own weight before
> reaching anywhere near that altitude. A cable made
> of carbon nanotubes
> MIGHT have the strength, but the resistance would be
> prohibitive, and the
> "whiplash" stresses and strains of high-altitude
> winds would destroy any
> such cable long before even the weight-collapse
> altitude was reached. This
> is why tethered balloons are seldom used for any
> purpose beyond a few
> thousand feet.
>      Quantitatively, I think you will find that,
> given the infrastructure
> needed, even at the limits of today's technologies,
> in terms of $/kg
> payload, this scheme would require a hundred-fold
> improvement to be as
> efficient as today's worst chemical-combustion
> propulsion systems.
>      Perhaps less daunting, though more unreliable,
> would be a way to
> capture and store energy from natural lightning
> strikes. It's just a
> question of lifter, payload, and crew surviving the
> initial system
> charge-up. ;-))
>
> Matt D.
>
>
>

 Thanks for the info. I found this site that says
tethered balloons are used up to 15,000 ft.

TETHERED AEROSTAT RADAR SYSTEM.
http://www2.acc.af.mil/library/factsheets/tars.html

 This page explains the tether made of Kevlar has
embedded electrical conductors within it to send power
up to the balloon, up to 80 kW, and metallic braids
within the tether are used to safely conduct lightning
to ground:

What Is Tether?
http://www.tcomlp.com/aerostats_What_teth.html

 This report recommends tethered balloons for
astronomical research at up to 12 km high, 40,000 ft:

POST: A polar stratospheric telescope for the
Antarctic.
Publications Astronomical Society of Australia, vol.
13, no. 1, p. 48-59.
http://adsabs.harvard.edu/cgi-bin/bib_query?1996PASA...13...48D
 [full text]

 This study recommends tethered ballon astronomy
platforms at 65,000 feet, 20 km:

Very high altitude tethered balloon feasibility study.
AIAA Lighter-Than-Air Systems Technology Conference,
11th, Clearwater Beach, FL, May 15-18, 1995, Technical
Papers (A95-30317 07-01), Washington, DC, American
Institute of Aeronautics and Astronautics, 1995, p.
46-51.
http://www.aiaa.org/content.cfm?pageid=406&gTable=mtgpaper&gID=82068

 This article is not available for free, but I gather
from the page freely available online that the authors
believe the tether can be made of Kevlar to reach this
altitude.
 This would be in the altitude range required for the
Tesla idea of wireless electrical transmission.



   Bob Clark




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