Long cables to power "ioncraft" to orbit?

[Pig Bladder]

Dear Robert Clark:



Corona inception in a vacuum is around 270 volts. What do you mean by
"immeasurably high"?

David A. Smith

I think this horse is long dead.

 

[Pat Flannery]

Key for lifter drive becoming a generally useful propulsion method is
an electrical power source lightweight enough to be lifted by the
lifter dirve. Electrostatic high voltage generators may prove to an
answer for such a power source.

I'd still just generate the energy on the ground, and beam it to it as
microwaves; the wide flat shape of the lifter would make an ideal shape
for a rectenna.

Pat

 

[Robert Clark]

Key for lifter drive becoming a generally useful propulsion method is
an electrical power source lightweight enough to be lifted by the
lifter dirve. Electrostatic high voltage generators may prove to an
answer for such a power source.
Electrostatic high voltage generators have existed since the 18th
century. They were earlier called electrostatic influence machines.
This page of Antonio Carlos M. de Queiroz calcutes the current that can
be generated by an electrostatic influence machine:

Maximum electric field.
http://www.coe.ufrj.br/~acmq/efield.html

(For anyone who had the same problem as I did opening this site, you
can get the Google cached version here:

Maximum electric field.
http://64.233.161.104/search?q=cache:Su6AOXBIC9EJ:www.coe.ufrj.br/~acmq/efield.html)

Note that it is dependent on the product of the dielectric constant
of air and the breakdown voltage of air.
Then since the dielectric constant of the air and vacuum are about
the same but the breakdown voltage of the vacuum is immeasurably
high, you can achieve much higher currents enclosing the device in a
vacuum.
Various types of electrostatic generators are described on this page
of de Queiroz:

Electrostatic Machines.
http://www.coe.ufrj.br/~acmq/electrostatic.html

Especially useful for our methods might be the Wimhurst, Wehrsen,
Holtz, or Bonetti machines. I believe these devices would be able to
deliver more current and therefore greater wattage for our application
than a Van de Graaff generator.
Another interesting possibility might be the voltage doubler. As the
name implies it doubles the applied voltage with each cyclic turn of
the rotors:

The Bohnenberger machine.
http://www.coe.ufrj.br/~acmq/bohnenberger.html

Take a look at the graph on this page to see how the voltage is
doubled at each cycle. The doublers are limited in voltage in air by
the sparking that is produced. The voltage possible in vacuum should be
markedly higher.
Another possibility might the generators that use a vertical cylinder
as a rotor. From de Queiroz "Maximum electric field" page you see the
current produced is proportional to the surface area of the rotor and
the speed of rotation. But there are limits to the rotational speed for
real materials since they would fall apart from the internal stresses.
Keeping the speed low but increasing the radius of a flat disc raises
the same problem because the speed on the edge of the disk will be
higher. However, a vertical cylinder solves this since you get
increased surface area by making the cylinder long while the internal
stresses from the rotation are only operating radially.
The key factor in using an electrostatic generator for the power
supply is that they can serve as both the source of the electrical
power and the source of the high voltage generation - you don't need
separate power supply and transformer.
That they act as source for high voltage is known, but the reason they
can act as the power source for our application is they are in effect
flywheel batteries. Then at launch you induce the rotors to spin at
high speed by either mechanical or electrical means and as with any
flywheel they would act as a means of power storage. Note that with the
most advanced flywheel batteries you enclose the flywheel in vacuum to
keep the time the flywheel spins to a longer period by reducing air
friction, and they also use magnetic bearings to reduce the friction
from the support of the rotor. Then this dovetails nicely with the
requirement to have them in vacuum to increase voltage attained.
A file in the Yahoo Lifters group calculates remarkable power
generation for a moderately sized vacuum electrostatic generator:

Lifters.
http://groups.yahoo.com/group/Lifters/

The file named "Electrostatic HV Supply.PDF" appears in the Files
section in that group. It was copied from a book on high voltage
generation and claims for a generator operating in high vacuum with 50
rotors, 4 feet in diameter rotating at 4,000 RPM could generate 1 MV
and 7 megawatts of power. Note that key in its being able to deliver
this power is the rotors operating in vacuum where much higher voltage
gradients are possible, 1 MV/cm or 100 MV/m in this case. In air you
might be able to get only 3 MV/m. Then assuming approx. a 1 to 1
thrust(in grams) to power(in watts) ratio, this could lift 7,000 kg.
Key would be making the rotors light weight. Then work on advanced
flywheel batteries that use carbon composites for the flywheel would be
helpful here:

Composite Rotor Lifetime Testing.
http://www.utexas.edu/research/cem/composite rotor testing.html

Flywheel Energy Storage.
http://www.upei.ca/~physics/p261/projects/flywheel1/flywheel1.htm

Flywheel Basics Tutorial.
http://rpm2.8k.com/basics.htm




Bob Clark

On this Powerlabs.org page I saw discussed use of a Dremel grinding
tool to generate high revolutions per second:

PowerLabs High Speed CD-Rom Experiments.
http://www.powerlabs.org/cdexplode.htm

This tool can generate 35,000 RPM or nearly 600 revolutions per second.
Perhaps this can be used to increase the current generated by an
electrostatic generator by increasing the rotation speed. See the
formula on de Queiroz's page for the current
generated:

Maximum electric field.
http://www.coe.ufrj.br/~acmq/efield.html

De Queiroz gives an example here of a rotor with 13 cm, 5", outer
diameter with a rotation speed of 40 revolutions per second generating
36 microamps. So at 600 turns/sec using the formula there should be 15
times the current or 540 microamps. Note too that in the example there
is a 9 cm inner diameter which reduces the surface area by about 1/2.
So for a solid disk at 13 cm diameter there would be about 1000
microamps, 1 milliamp.
Dremel grinding tools are available for reasonably low prices. Here's
one for $29.00 US:

Wholesale Dremel Type Rotary Electric Grinder kit NEW.
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&category=29528&item=4389954711


You could also increase the current by increasing the number of rotors
(but see the caution below.)
Note that the idea is to see if these electrostatic generators could
provide a self-contained power unit for a lifter. But at first we want
to see if they can supply sufficient power/current to raise just the
lifter. So in the first experiments you just use already existing
electrostatic generators on the ground, which are not optimized to be
lightweight.
Then we also want to see how the energy of rotation is stored and
converted into electrostatic energy. So once it is confirmed the
generators can provide sufficient power, you disconnect the Dremel to
see how long the rotor can spin fast enough to provide sufficient power
to raise the lifter.
Note that these first experiments are done in air so the air friction
will significantly reduce the rotation time once the Dremel is
disconnected. Later the idea would be to contain the rotor in vacuum.
This will increase the rotation time and at the same time increase the
voltage possible 30 to 50 times. (Note that to get this voltage
increase, it has to be a very high vacuum since reducing the pressure
can actually decrease the breakdown voltage until very high vacuum is
reached.)

CAUTIONS!
Note that on the Powerlabs page they were attempting to cause a CD disk
to disintegrate by spinning at the highest speed of the Dremel. In
*this* experiment they had to additionally strike the spinning CD with
another CD to get the spinning CD to shatter. But there have been cases
where CD's have shattered at lower speeds than 35,000 RPM. Also after
rotating at this speed for some time, the CD would suffer stress
fatigue and would become even more likely to shatter. So even if you
spin a rotor at a high speed for some time, at a later time it can
still shatter at that very same speed.
Acrylic if that is used for the rotor probably would have comparable
tensile strength as a CD. It is *strongly* advised that the rotor be
gradually brought up to higher speeds stepwise. And it is *strongly*
advised that the rotor be behind a protective wall during these
experiments. You can view the experiment by video camera or by mirrors
(metal so as not to shatter.) In the Powerlabs experiments the
experimenter held the Dremel with the spinning CD out in front of him.
This is strongly disadvised.
Note also if you use more than one rotor on a single Dremel this could
cause wobbling which could put more stress on the rotors increasing the
chance of shatter and also making the directions the shards would go
more unpredictable.
Also, if you increase the diameter of the rotors the speed at the edge
of the rotor is also increased thereby increasing the chance of
shattering. Moreover, the Dremels are actually designed for rather
small diameter grinding attachments. Large diameter rotors could damage
the Dremel motor.


Bob Clark