Actually after rethinking the issue and getting some sleep, your stationary cavity makes sense now -your thrust is exerted against the "high pressure" gas supply you mentioned - much easier than moving the cavity.
Horace I followed circulating monatomic gas through variations in the plate spacing to initiate plasma by snaking gas back and forth between different size cavities and can see where this would increase the inertia of your fixture but I have a feeling you may need to move the cavities as well if you want to create thrust. By circulating your "cells" as hydrogenated porous metal powder thru axial coils while turning the plasma on and off to create a differential. I noticed some materials smart people on this list - can anyone suggest a good porous conductive powder -Calcium? Fran
