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Old 19th August 2009, 11:20 PM   #294
Reality Check
Penultimate Amazing
Join Date: Mar 2008
Location: New Zealand
Posts: 26,873
Exclamation EDM in the EC idea needs a dielectric material which does not exist!

I had foolishly thought that the proposers of the electric comet idea knew a bit about electrical discharge machining. It seems that they do not.

EC universe: EDM removes material from the surface of comets and creates water from the material somehow.

Real universe:
Electric discharge machining (EDM), sometimes colloquially also referred to as spark machining, spark eroding, burning, die sinking or wire erosion,[1] is a manufacturing process whereby a wanted shape of an object, called workpiece, is obtained using electrical discharges (sparks). The material removal from the workpiece occurs by a series of rapidly recurring current discharges between two electrodes, separated by a dielectric liquid and subject to an electric voltage. One of the electrodes is called tool-electrode and is sometimes simply referred to as ‘tool’ or ‘electrode’, whereas the other is called workpiece-electrode, commonly abbreviated in ‘workpiece’. When the distance between the two electrodes is reduced, the intensity of the electric field in the volume between the electrodes is expected to become larger than the strength of the dielectric (at least in some point(s)) and therefore the dielectric breaks allowing some current to flow between the two electrodes.
If there is no dielectric material between the electrodes then there are no sparks and there is no machining.
In the EDM idea the workpiece-electrode is the surface of the comet. I do not know what the tool-electrode is (the coma?, the tails? the solar wind? maybe the Sun!).

There is no dielectric material above the surface of a comet - just lots of highly conductive plasma in the coma, solar wind and tail.
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