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Re: Towards the autonomous lifter - electrostatic voltage generators.



Original poster: Robert Clark <bobbygc2001@xxxxxxxxx>

--- Tesla list <tesla@xxxxxxxxxx> wrote:

> Original poster: Steve Conner <steve@xxxxxxxxxxxx>
>
> I'm very skeptical about this line of argument for
> the following reasons-
>
> 1) Vacuum chambers are HEAVY! So I don't think
> there's any point in trying
> to make an electrostatic generator in a vacuum
> chamber. The extra weight of
> the chamber would probably more than nullify the
> extra lift due to the
> higher output. If I were trying to do this I would
> start with a high
> frequency Cockroft-Walton multiplier running off
> lithium polymer batteries.
> These batteries are used in radio controlled model
> airplanes and
> helicopters, and can easily put out enough power to
> lift their own weight
> when used with an electric motor and propeller.
>
>
> 2) You might be thinking that the whole lifter is
> designed to fly in space
> so no vacuum chamber is needed for the generator.
> Lifters can't fly in a
> vacuum because they work by ion wind. What's more,
> there's practically no
> gravity out there so you don't need lift in the
> first place!
>
> You could of course supply your own source of
> propellant, but then you have
> just built an ion engine. These have been used on
> spacecraft for years now:
>
>
http://www.bbc.co.uk/science/space/exploration/futurespaceflight/ionengines.shtml
>
> If you like, these are the "lifters that made it"
>
> Steve Conner
>
>

 Thanks for the response. I'm not arguing in favor of
using the lifters in vacuum. I'm basing my suggestions
on the idea the lifters work by electrohydrodynamic
propulsion(EHD), which arises from propelling an
ionized fluid with electric fields.
 The use of the vacuum is only to provide a means of
increasing the voltage produced by an electrostatic
generator, and to increase the time the rotor would
rotate independently of a driving motor. Only the
rotors in the generator would be enclosed in the
vacuum. The lifter would operate in air.
 I looked up some references to vacuum chamber wall
thickness compared to diameter. There aren't that many
available on the net, as compared to for example the
many references on the thickness required for a
cylinder containing highly pressurized gases (the
opposite problem.)
 Here's one page that gives optimism that such a
chamber can be made lightweight:

Hemispherical Beryllium Vacuum Windows.
http://www.ktekintl.com/Be/bw_spher.html

 The diameter to wall thickness ratio of the 20 cm
diamter chamber offered is 333 to 1. I calculated the
material volume of a full sphere of 20 cm inner
diameter and .06 cm thickness as 75.85 cm^3. So
composed of beryllium at 1.8 g/cc density, this would
weigh 136 g.
 However, the hemispherical chambers offered by this
company have rather thick flanges attached at the
base. I don't know if these are required to maintain
the vacuum integrity. I may be that for a single full
sphere they would not be required.
 But a spherical chamber is actually overkill because
the rotor is actually flat. IF the same thickness
could be maintained for a flat chamber, this would
result in a significant reduction in weight.
 A material such as beryllium is ideal for a
lightweight chamber because of its high strength to
weight ratio. However, beryllium is quite expensive
and also quite toxic. Therefore a better material for
our purposes might be silicon carbide, which also has
a high strength to weight ratio.

 I also would like to see a lifter made using a
Cockroft-Walton multiplier. A possible problem though
might still be the weight of the battery. The weight
of a battery plus a transformer has been the main
problem of coming up with a self-contained power
supply before for a lifter. A Cockroft-Walton
multiplier eliminating the need for a transformer
might just make it work.


Bob Clark




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