Re: Spark length dependence on air pressure.

["Tesla list" <tesla@xxxxxxxxxx>]

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.