In article
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wrote:

See:

http://blog.wired.com/defense/2008/0...e-buildin.html

Is it really "impossible"?

You can see how it works in
http://emdrive.com/principle.html

It works the same way as storing compressed gas in a tank shaped like a
truncated cone. On one end is, e.g. a 20 cm diameter endcap, on the
other is a 10 cm endcap. The areas are different by 235 cm^2, so if
you pressurize the tank to 10 atmospheres (1e6 N/m^2) you will get a
difference in force between the two endcaps of 23kN, or a couple of
tons-force.

That's why pressurized gas tanks are precisely manufactured cylinders
instead of cones: otherwise there would be too much danger of one of
them coming loose and flying across the landscape, picking up speed
with each passing second until it either hits something or leaves the
atmosphere, accelerating forever through space until it passes
lightspeed.

--
David M. Palmer (formerly @clark.net, @ematic.com)