Long cables to power "ioncraft" to orbit?

[Pat Flannery]

You can call it MHD if you want. I'm referring to any method of
propulsion that uses either electrical or magnetic fields to propel air
that has been ionized by electrical means or otherwise.
Lifters also can work on AC current. Then in addition to the force
produced by the asymmetric electric field you could get a force due to
the Lorentz force arising from the magnetic field.

If you ever see a copy, get your hands on "The Future Of Flight" by Leik
Myrabo and Dean Ing (Baen Books, 1985, ISBN 0-671-55941-9 in the
paperback edition) it's chock full of exotic propulsion ideas for
spacecraft using laser, ion, and MHD drive- most powered by beamed
energy systems.

Pat

 

[bz]

Oh, I froze on real good- I froze on so good that I went jumping
violently down the boulevard with the electrified rod clamped tightly in
my hand and sparks coming out of my feet on each impact with the ground-
as the connection to the rod stuck in next to the anthill was completed.

I don't know why I get the picture of Coyote and Roadrunner. Coyote trying
to electrocute Roadrunner (ants?).

I finally got far enough away that I pulled the wire off the coil, but
my whole right arm's muscles were contracted, and it was sore for a few
hours.

Do I need to say that you were lucky? AC is especially nasty if it transits
across the chest. Tends to make the heart go into ventricular fibrillation.

Death results soon thereafter without CPR and defibrillation.

That was the last time I used a bread bag over an oven mit as a means of
high voltage protection.

Oven mits tend to retain moisture. Bread bags often have pin holes. And
they are not thick enough to play with 20 kv either, as I am sure you now
appreciate.

I suspect it was AC also; It was basically just a big transformer, but
boy could it generate a hot arc..it had a superheated purple/yellow
plasma flame coming off the top of it.

I take it that you also had some burns on your feet?

You know those Ionic Breeze air cleaners? If we were to take around ten
thousand of those and weld them to a spaceship, and we were in a gaseous
nebula... did I ever tell you about my plan for a rocket engine that
generates almost no thrust, but nevertheless creates an incredible
amount of noise? ;-)

In a vacuum, when you scream, no one can hear you!


--
bz

please pardon my infinite ignorance, the set-of-things-I-do-not-know is an
infinite set.

[email protected]


--
bz

please pardon my infinite ignorance, the set-of-things-I-do-not-know is an
infinite set.

[email protected] remove ch100-5 to avoid spam trap

 

[bz]

It should also cut down on the danger of arcing shorting out the system.

The breakdown voltage of air _decreases_ as the air pressure goes down.

Paschen's Law Vs=f(N ds) where Vs is sparking potential, ds is sparking
distance and N is gas number density.

Has anyone stacked a few lifters one on top of the other and seen if
each layer continues to accelerate the air downwards at higher velocity,
thereby generating more thrust?

--
bz

please pardon my infinite ignorance, the set-of-things-I-do-not-know is an
infinite set.

[email protected] remove ch100-5 to avoid spam trap

 

[Pat Flannery]

I don't know why I get the picture of Coyote and Roadrunner. Coyote trying
to electrocute Roadrunner (ants?).

I never was able to lure the grackle between the two contact plates with
the slice of bread between them- it thought it looked suspicious, and it
was right to think it looked suspicious.
Vicious they are- stupid they ain't.

Do I need to say that you were lucky? AC is especially nasty if it transits
across the chest. Tends to make the heart go into ventricular fibrillation.

I got zapped by the thing about three times total before just deciding
to leave it alone it did have a very deleterious effect on the ants
though while it was in operation...not as deleterious effect as the
molten lead had on the same anthill a couple of years later, but
effective none the less.

Death results soon thereafter without CPR and defibrillation.

My friend said he couldn't believe I could jump that high; I told him
that the electricity really helps your muscle response.

Oven mits tend to retain moisture. Bread bags often have pin holes. And
they are not thick enough to play with 20 kv either, as I am sure you now
appreciate.

I was thinking about the incident last night and realized that I was
doing this within six feet of a buried telephone cable and gas main...so
after the electricity sets off the leaking gas, the people try to call
the fire department- if they are lucky, the phones just don't work- if
they are unlucky, they get lightning in their ear.

I take it that you also had some burns on your feet?

Actually I didn't get any burns from it; the contact seemed to have
occurred over a wide enough area that no particular area got burned as
no arc occurred at any one place; It dawned on my when I was thinking
about it the the power was going through the soil in preference to my
body as long as the rod I had grabbed onto was in contact with the
ground, it was only after I pulled it clear of the soil that my body
became the route it decided to travel by back to the other rod, and that
was via my feet. I did get a electrical burn years later off of a
discharging microwave oven capacitor though. That went in the right hand
and out the left hand with an audible "bang" noise, and left a small
burn at either end.
Oh, and while we are the subject of fooling around with
electricity...you know those glass plasma spheres that use the Tesla
coil to generate the glowing gases that you see in stores? Well, don't
wrap wire around the outside of one to see if you can generate a current
in it via induction. You can, and although you will notice only a sight
tingling as you touch the end of the wire, it will give you some nifty
and deep RF burns.
On the other hand, if you want to get rid of a wart using technology
that looks like it came straight out of a Flash Gordon comic...

Pat

 

[Pat Flannery]

The breakdown voltage of air _decreases_ as the air pressure goes down.

Paschen's Law Vs=f(N ds) where Vs is sparking potential, ds is sparking
distance and N is gas number density.

Okay... but other than that... :-[

Pat

 

[bz]

I did get a electrical burn years later off of a
discharging microwave oven capacitor though. That went in the right hand
and out the left hand with an audible "bang" noise, and left a small
burn at either end.

In the mid 70s I fixed electronic equipment on ships for a living.

I was on the bridge of a ship, working on the echo sounder, removing a
nurled nut holding part of the transmitter to its mounts (without first
discharging the capacitors!) when the skin on the surface of my thumb
provided a discharge path from the capacitor to ground.

Sound like a shotgun going off. Bright flash. White path along surface of
skin that took a while to go away.

I was lucky.

I think it was about 3KV, 0.05 mfd.

I think most of the discharge went through ionized air/skin because I never
felt anything.

--
bz

please pardon my infinite ignorance, the set-of-things-I-do-not-know is an
infinite set.

[email protected] remove ch100-5 to avoid spam trap

 

[N:dlzc D:aol T:com \(dlzc\)]

Dear Pat Flannery:

The breakdown voltage of air _decreases_ as the
air pressure goes down.

Paschen's Law Vs=f(N ds) where Vs is sparking
potential, ds is sparking distance and N is gas
number density.

Okay... but other than that... :-[

I'm not sure you understand, so...
As the corona inception voltage goes down, so does the average
velocity of the ions leaving. If the velocity goes down, the
thrust goes down by the square of the velocity. Altogether a bad
thing, epecially when rarefied air presents a good opportunity to
reduce drag.

David A. Smith

 

[N:dlzc D:aol T:com \(dlzc\)]

Dear Robert Clark:

You can call it MHD if you want.

Let me do a little house cleaning:
MHD = MagnetoHydroDynamics

I'm referring to any method of
propulsion that uses either electrical or magnetic
fields to propel air that has been ionized by
electrical means or otherwise. Lifters also can
work on AC current.

MHD uses AC primarily.

Then in addition to the force produced by the
asymmetric electric field you could get a force
due to the Lorentz force arising from the
magnetic field.

David A. Smith

 

[Robert Clark]

...
Look at the table near the bottom on this page:

Lifter Theory.
http://jnaudin.free.fr/html/lf­theory.htm

The last line in this table labled Thrust(g)/Power(W) ratio gives the
weight that could be lifted for given power with the air density
available at ground level. It is given as 0.509, or about 2 to 1 for
power in watts required to lift a weight in grams.
This is at ground level. The thrust available becomes proportionally
less as the air density decreases so you arrange your trajectory so
that most of the powered flight occurs in the lower atmosphere. Lifter
thrust ratios at this level or better have already been demonstrated
for small test cases.
Here's a case where 185g weight of the lifter plus payload was lifted
using 200 watts of power. This is about a 1 to 1 ratio:

Saviour, the WINNER OF THE 100g of PAYLOAD CHALLENGE.
http://jlnlabs.imars.com/lifters/100gwin/index.htm

The next step is to test that this thrust ratio will hold at the
kilowatt range. Many people already own electrical generators that can
put out a few kilowatts of power. They are used for example for
generators for RV's, stand-by generators, picnic trips, etc.
This page shows such generators can be had for a few hundred dollars:

Electric Generator Store - Portable Generator, Diesel Generators ...
http://www.electricgeneratorstore.com/

For example using the 1 to 1 thruster ratio, the 3250 watt generator
advertised for $500 could lift 3.25 kilos, about 7 pounds.


Bob Clark

I was attempting to encourage extending the work done by amateurs with
lifters to the kilowatts of power range. However, I am informed that
using high voltages while at the same time having high wattage means
the amperage would also be high. This can potentially be lethal.
There are relatively inexpensive ways of transforming the low voltage
put out by electrical generators to the tens of thousands of volts you
need for the lifters. If you have experience working with high voltage
and amperage, then you already know what they are.
It should not be attempted unless you are already well experienced
with working on and in high power electrical supplies.


Bob Clark

 

[Dishman]

I was attempting to encourage extending the work done by amateurs with
lifters to the kilowatts of power range. ...

A 3250 watt generator will weigh a lot more than 7 pounds.
The simple approach needs a lift greater than the weight
including the fuel. What you have then is an engine
(generator plus lifter) which derives thrust from fuel
using the air as reaction mass. You would get far better
efficiency from a simple jet engine.

So your idea is to leave the engine and fuel on the ground
which sounds good. However you then have the problem of
getting the power to the vehicle. Unless the mass of the
cable is less than the mass of the generator and fuel, you
gain nothing.

You are limited by voltage so assuming you use the maximum
feasible, the current is proportional to the power and the
cable mass per unit length is proportional to current for
a flat thin ribbon (maximum surface area to dissipate heat).

Information on the conductor parameters and a bit of maths
should then give you the maximum cable length, or distance
between cable-supporting lifters and so on.

All of this will let you gently raise your payload to some
altitude but won't get any appreciable speed and the need
for reaching orbit is horizontal speed, not height.

A balloon remains more practical and cheaper.

George

 

[Pat Flannery]

In the mid 70s I fixed electronic equipment on ships for a living.

I was on the bridge of a ship, working on the echo sounder, removing a
nurled nut holding part of the transmitter to its mounts (without first
discharging the capacitors!) when the skin on the surface of my thumb
provided a discharge path from the capacitor to ground.

Sound like a shotgun going off. Bright flash. White path along surface of
skin that took a while to go away.

I was lucky.

I think it was about 3KV, 0.05 mfd.

I think most of the discharge went through ionized air/skin because I never
felt anything.

In my case I felt like a fool because it had a huge label on it warning
you to discharge it prior to doing any work on the oven; the oven was a
first generation microwave from the mid 70's and the capacitor was a
thing the size of a small hip flask.
I really felt it; I got tossed around three feet and had spots before my
eyes.

Pat

 

[Pat Flannery]

I'm not sure you understand, so...
As the corona inception voltage goes down, so does the average
velocity of the ions leaving. If the velocity goes down, the
thrust goes down by the square of the velocity. Altogether a bad
thing, epecially when rarefied air presents a good opportunity to
reduce drag.

Yeah I got your point; there's something else to take into consideration
here- what happens when the Lifter hits the ozonosphere? Isn't ozone
electrically conductive, and won't that short the whole works out?

Pat

 

[bz]

Yeah I got your point; there's something else to take into consideration
here- what happens when the Lifter hits the ozonosphere? Isn't ozone
electrically conductive, and won't that short the whole works out?

Not to mention what happens when it hits a cloud, or icing conditions, or
when the metal happens to be below the dewpoint and water starts to
condense on everything.


--
bz

please pardon my infinite ignorance, the set-of-things-I-do-not-know is an
infinite set.

[email protected] remove ch100-5 to avoid spam trap

 

[N:dlzc D:aol T:com \(dlzc\)]

Dear Pat Flannery:

Yeah I got your point; there's something else
to take into consideration here- what happens
when the Lifter hits the ozonosphere?
*Ionosphere*.

Isn't ozone electrically conductive, and won't that short
the whole works out?

No, it is no more conductive than oxygen. In fact, since it is
polar, it will actually increase the energy required to start
"coronation".

David A. Smith

 

[Puppet_Sock]

Eliminate t from these two equations to get 2*a*s=v^2. If you want v to
equal orbital velocity, about 8000m/s, then a*s = 32*10^6. If you want
s , which will be the length of the cable, to be 100,000m, then a = 320
m/s^2, about 32 g's (using g as approx. 10 m/s^2).

Sigh. And how much does a 100 km cable weigh under 32 g? And what
is going to support that? Certainly not the cable. We don't have
cables that can support their own weight at 100 km length under
1 g, never mind 32 g. Suddenly, you are back to the effective
length of 3000 km or so.
Socks

 

[Robert Clark]

Sigh. And how much does a 100 km cable weigh under 32 g? And what
is going to support that? Certainly not the cable. We don't have
cables that can support their own weight at 100 km length under
1 g, never mind 32 g. Suddenly, you are back to the effective
length of 3000 km or so.
Socks

Yeah, you probably would not want to operate at 32 g's, unless you
found some way of coming up with a super-lightweight cables (I have an
idea about that.)
But we several materials that can support their own weight at over 100
km, Kevlar, Spectra, carbon fibers, etc:

From: Dani Eder <[email protected]>
Subject: Re: space elevator / cable
Date: May 08 1997
Newsgroups: sci.space.tech

Spectra 1000 has the characteristic length of 315 km!?!
That might be enough for me to reconsider a tapered tether concept.
thats 7 times the strongest fiber I had specs for(c. 1960's tech)
-

And Toray Industries (http://www.toray.com/html/carbon_fibers.html)
T-1000G carbon fiber has a strength of 924,000 psi and a density of
0.0654 lb/cu inch. Therefore it has a characteristic length of
14.1 million inches, or 359 km."
http://yarchive.net/space/exotic/carbon_fiber.html

The simplest way would probably be to have the horizontal track be
covered by cable lying on the ground and only the vertical distance of
cable be supported by the propulsive method. This would result in a
much lower acceleration because it takes place over a longer distance
and also a much lower weight of cable that had to be supported.
Keep in mind that whatever the mass of the cable that had to be
supported in the air, quite likely you would want the cable to have its
own propulsion all alongs its length rather than having it come totally
from the spacecraft itself.



Bob Clark

 

[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

 

[N:dlzc D:aol T:com \(dlzc\)]

Dear Robert Clark:

....

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,

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

David A. Smith

 

[Uncle Al]

Key for lifter drive becoming a generally useful propulsion method is
an electrical power source lightweight enough to be lifted by the
lifter dirve.

[snip crap]

Idiot. Lifter thrust scales as no more than surface area. Mass
increases as volume. It's bullshit. Only payload makes a profit -
hence the execrable Space Scuttle being forever grounded for its
$30/gram LEO boost cost.

 

[Robert Clark]

I was attempting to encourage extending the work done by amateurs with
lifters to the kilowatts of power range. However, I am informed that
using high voltages while at the same time having high wattage means
the amperage would also be high. This can potentially be lethal.
There are relatively inexpensive ways of transforming the low voltage
put out by electrical generators to the tens of thousands of volts you
need for the lifters. If you have experience working with high voltage
and amperage, then you already know what they are.
It should not be attempted unless you are already well experienced
with working on and in high power electrical supplies.


Bob Clark

It seems to me the efficiency can't get any worse at
high power, where efficiency is thrust to power ratio. For
example Blaze Labs was able to lift 185 grams using
200 watts. Therefore all you would have to do with
3000 watts would be to distribute this power equally
to 15 lifters of the Blaze Labs design physically
connected together in a single layer and you would be
able to lift 15*185 = 2775 grams. You might be able to
maintain safety by making sure the wires for separate
lifters do not touch. A good way to do this is in fact
to use completely separate but identical power supplies
for each lifter and ensuring that though the lifters
are physically connected, none of the conducting parts touch.
Since drag increases in proportion to cross-sectional
area the drag would also only increase in proportion
to the size. You might also be able to get less drag by
stacking the lifters on top of one another. However,
Blaze Labs believes their experiments show this would
*reduce* the thrust to power ratio.
But the key question that needs to be answered is how
does the thrust change at high air speed.


Bob Clark