Kyle and Michel,

You have likely seen this paper already,
but if you haven't you can download it (about 1MB) from here:

http://jlnlabs.imars.com/lifters/arl_fac/0211001.pdf

Here is the paper's abstract:

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Army Research Laboratory
Adelphi, MD 20783-1197

Force on an Asymmetric Capacitor by Thomas B. Bahder and Chris Fazi

ARL-TR-XXX March 2003

Approved for public release, distribution unlimited.

When a high voltage (~30 kV) is applied to a capacitor whose electrodes have
different physical dimensions, the capacitor experiences a net force toward
the smaller electrode (Biefeld-Brown effect). We have verified this effect
by building four capacitors of different shapes. The effect may have
applications to vehicle propulsion and dielectric pumps. We review the
history of this effect briefly through the history of patents by Thomas
Townsend Brown. At present, the physical basis for the Biefeld-Brown
effect is not understood. The order of magnitude of the net force on the
asymmetric capacitor is estimated assuming two different mechanisms of
charge conduction between its electrodes: ballistic ionic wind and ionic
drift. The calculations indicate that ionic wind is at least three orders of
magnitude too small to explain the magnitude of the observed force on the
capacitor. The ionic drift transport assumption leads to the correct order
of magnitude for the force, however, it is difficult to see how ionic drift
enters into the theory. Finally, we present a detailed thermodynamic
treatment of the net force on an asymmetric capacitor. In the future, to
understand this effect, a detailed theoretical model must be constructed
that takes into account plasma effects: ionization of gas (or air) in the
high electric field region, charge transport, and resulting dynamic forces
on the electrodes. The next series of experiments should determine whether
the effect occurs in vacuum, and a careful study should be carried out to
determine the dependence of the observed force on gas pressure, gas species
and applied voltage.
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