> I haven't been following the developments -- has anyone actually succeeded
> in building a lifter with an on-board power source? Now, THAT would be cool.

The closest anyone has come has been to use a blimp with an onboard
power supply to hold a lifter up, and then use the lifter to provide thrust.

If increasing the capacitance helps, then I'm envisioning using a rolled
sheet of aerogel with the wire electrode embedded  at the top and the
sheet electrode at the "bottom", with small gaps between successive
layers (imagine a loosely wound toilet roll).  If one were to make that
as large as, say, the engine on a 747, how much thrust could that make?*

Now imagine five or six of these things, slung under a wing, with the
wing's top surface covered in solar cells, and you have an aircraft with
no moving parts to break (or very few, for control surfaces).  Granted, it
would likely be VERY slow, with a miserable time-to-altitude, but once
at altitude, it would have an essentially unlimited loiter time.  I can
think of a few good uses for such a craft.

Mike H.

*It should be relatively easy to figure that out.  Let's see:  I seem to
remember seeing a six-foot equilateral triangle lifter that weighed about
nine ounces.  So, we have 18 feet of capacitor, with a dielectric constant
~1.  Assuming thrust is directly proportional to lift (may not be a safe
assumption; that was why I posited this question in the first place), it
should be fairly easy to boost that by 100 fold using a suitable dielectric.
So, we have roughly 1 ounce of lift per 2 feet of lifter, going to 100 ounces
per 2 feet with the improved dielectric.  A roll of material is approximately
L units long for pi(Ro^2-Ri^2)/t, where Ro is outer thickness, Ri is core
thickness, and t is the thickness of the layers.  We'll give each layer a
thickness of 1 inch, call the core 0, and the outer radius 4 feet.  That
gives us 600 feet of lifter, or 300 ounces of thrust with conventional
methods.  Almost 19 pounds of thrust.  Not very impressive.  BUT, if
increasing the capacitance 100 fold increases the thrust 100 fold, we
have a much more interesting situation.  And since the thrust increases
as the square of the outer radius, even going up a few feet helps a lot:
give our engine a 10 foot radius and we now have over six times the
thrust.  Give our contraption six of them, and we approach 700 pounds
of thrust.  Take away the need for fuel and put it at a high altitude,
where drag is lessened (may need to tow it up or use other novel
deployment methods), and you've created a poor man's
geosynchronous satellite.  And that's assuming no gain from capacitance
boosting (which I suspect there won't be).

An interesting possiblity which just occured to me (for anyone still
reading): let's say that the lifter works by the skewing of field lines
created between a point-source charge (the wire) and a line source
charge (the foil)(looking at it cross-sectionally).  If the lifter is simply
accelerating already present ions, not creating its own, at high
altitudes, the atmosphere contains significantly more ions than it
does at sea level.  Perhaps that would boost thrust?

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