Michel Jullian wrote: > The short answer is "in practice, not in this case". > > In Sigmond's derivation d is the z- (usually vertical) distance traveled by > the single ion under study. Since the highest density of ions takes the > shortest route, for most (but not all) lifter designs one can make the > approximation of the same z-distance d (the gap length) for all ions, hence > the I*d/mu thrust formula obtained by summing all the q*d/mu momentums > contributed by all the ions crossing the gap in one second. In those lifters > the exact shape of the collector doesn't matter, whether wing shaped or round > tube or plane mesh.
If the thrust can be increased by increasing the gap distance, how large can the gap be made? > But there are exceptions, e.g. in my trough shaped mesh design as I explained > the ions fan out, so they travel very different z-distances, so the X-to-plane > I*d/mu formula doesn't apply. If you do the (simple) maths you find: > > Thrust(line to half cylinder) = 2/pi * I*d/mu It doesn't depend on the width of the trough? > Michel > > P.S. You seem quite interested in this matter Harry, are you planning a lifter > construction project? No plans yet. Understanding lifters is my project. Harry > ----- Original Message ----- > From: "Harry Veeder" <[EMAIL PROTECTED]> > To: <[email protected]> > Sent: Saturday, February 24, 2007 8:45 AM > Subject: [Vo]: Lifter electrode geometries > > >> >> Michel, >> >> Reading your attachment, I noticed the derived formula for the force on the >> ions appears to be specific to a particular anode and cathode geometry. >> >> i.e. It says "d = distance point-plane", which I take to mean >> the gap between a wire-like anode and the upper edge of skirt-like cathode. >> >> Since the geometry of the cathode is different in the tubular lifter >> wouldn't the derived formula be different too? >> >> Harry >> >
