Long cables to power "ioncraft" to orbit?

Rich Grise wrote in news: snipped-for-privacy@example.net:

You would certainly have one heck of a pair of jumper cables. :)

: > "There are known knowns. These are things that we know we know. : > There are known unknowns. That is to say, there are some : > things that we know we don't know. But there are also unknown : > unknowns. These are things we don't know we don't know." : > -Secretary of Defense Donald Rumsfeld

: If Rummy really said this, then he is much more widely read than I : would have believed. This is a variation of a quotation from Lady : Burton, attributed as an 'Arabian Proverb': : "Men are four: : He who knows not and knows not he knows not, he is a fool--shun him; : He who knows not and knows he knows not, he is simple--teach him; : He who knows and knows not he knows, he is asleep--wake him; : He who knows and knows he knows, he is wise--follow him!"

The question is, which one is Rumsfeld?

: Tom Davidson : Richmond, VA

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Just as with electrical power transmission over long distances, you will use very high voltage, probably in the megavolt range, that is, if you want to lift megakilos. In the demonstrations for small lifters, kilovolts were used to lift only a few grams a few feet. Since the lifter uses air for its reaction mass, you could use a higher acceleration than that normally used for rockets to reach orbital velocity at a lower altitude so the air is at sufficient density. But this would reduce the lift capacity. That is, if you accelerated at 3.6 g's, you could lift one third the mass than at 1.2 g's. Or you could use a shallower trajectory than that used by rockets so that most of the acceleration phase stays in the lower atmosphere. But this would necessitate a longer and heavier cable. Probably a combination of these would be optimal.

Bob Clark

Lifters have only been proposed for spacecraft propulsion by the "asymmetric capacitor" nuts who claim they work in vacuum with no reaction mass. It may be useful for high altitude launch, though. Lifters should be able to hover in the no-man's land above aircraft and balloons and below stable orbit altitude where only rockets make brief visits. A gentle ride through the thick atmosphere and separation in near vacuum should make it much easier for the upper stage.

The wispy wire mesh structure of an ion lifter should make a good recantenna for transmitting power by microwave without a big increase in total weight. Transmission efficiencies in the two-digit percentage range have been demonstrated over long distances. I believe this should be much more practical than cables - assuming the lifter itself is up to the task.

Lifter efficiency should probably need to be improved by almost an order of magnitude. Evgenij Barsoukov (original source of the lifter theory page you refer to) has some promising ideas for improving efficiency. He has derived equasions that accurately predict ion lifter performance and seems to be one of the few people in the lifter scene who really know what they are talking about.

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Such experiments are being conducted:

This is from the 2nd Beamed Energy Symposium:

BEAMED ENERGY PROPULSION: Second International Symposium on Beamed Energy Propulsion.

A possible problem here is the power drop off with long distances, say at the several kilometer range. You might need an exorbitant amount of energy to be beamed in order to receive megawatts to gigawatts at the vehicle. With the cable, a simple estimation shows you would only lose a few percent from gigawatts of power over a hundred kilometers if the voltage was kept in the megavolts range and you used highly conductive aluminum. Beamed energy is being investigated by Leik Myrabo for his "Lightcraft." Admittedly this is using a different propulsion method but it may be indicative of the energy requirements for beamed propulsion:

Highways of Light, Scientific American, February 1999,

The Myrabo laser system uses a 10 kilowatt laser to lift a 50 gram Lightcraft about 100 ft. in the air. This is a 200 to 1 ratio of power in watts used to the weight lifted in grams. Their goal is to lift a 1 kilo craft to orbit using a 1 megawatt laser. This is a 1000 to 1 ratio of power used to weight lifted. Myrabo et.al. are also investigating a microwave version of the Lightcraft:

1. MICROWAVE LIGHTCRAFT.
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Here, 30 megawatts would be used to launch a 30 kilogram craft. This is a 1000 to 1 ratio of power in watts used to the weight lifted in grams. In the cable-powered lifter scenario it's about 2 to 1. In any case we don't have laser beams or microwave tranmitters that can put out gigawatts of power. I'm suggesting we have generators that can put out this much power. We could begin start the process to start lifting megakilo payloads *tomorrow*.

Bob Clark

snipped-for-privacy@yahoo.com wrote in news:1116571140.981894.102730 @g44g2000cwa.googlegroups.com:

Unforetunately, you almost certainly can't scale up the voltage significantly.

You will get arcing if you go up on the voltage, rather than ions.

Even if you could scale up the voltage, you would have two MAJOR problems.

That reminds me of one other problem. Weather. Humidity. The launch site will need to be in an area with very dry climate.

High humidity, clouds, or rain, will be very bad for such a device.

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Those interested in this might like to follow up the following links:

Gary Williams

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You would locate the launcher at the gigawatt scale at very dry areas. While transmission lines typically carry hundreds of kilovolts some do go up to a million volts. Using voltages in the hundreds of kilovolt range, power stations already exist that transmit gigawatts of power over hundreds of kilometers:

Quebec - New England Transmission.

Bob Clark

I don't recall a detailed explanation being in the book, but friction due to atmospheric drag would slow the bottom of the tether pretty quickly so as to cause problems, then once it's unstable it's manure and impellor time.

Ken

"Robert Clark" wrote in news: snipped-for-privacy@g44g2000cwa.googlegroups.com:

I haven't found any 1 MV transmission lines. 450 kV is the highest I saw, but I did find some cool pictures of arcs and sparks.

Also some real neat looking pictures of the results of 'quarter shrinkers'. Which use very high pulsed magnetic fields to shrink coins.

I dropped my jaw to hear this from a dais located in Washington D. C. He also did other things that were fraught with intelligence.

Yes, these types fixed his behaviour. Now anything that is decided or accomplished using brains, as they should be used, will not be documented. I drove down to Bethesda a couple of years ago and kept looking for the toll booth where everybody had to hand in his/her organ that contains common sense.

I got that book. I've read the first two chapters. I spent my dreamtime last night editing my mental data base. I'm so tired.

/BAH

Subtract a hundred and four for e-mail.

Yep.

Indeed. Would be dangerous to act otherwise.

:-)))

Well, let me know what you think, when you finish.

Mati Meron | "When you argue with a fool, snipped-for-privacy@cars.uchicago.edu | chances are he is doing just the same"

This irritates the hell out of me. How am I supposed to learn stuff if those who have the knowledge can't make it available? Politics have already sewn distribution of certain doors shut. When will the intelligentsia finish with mundane things like science and personal finances?

Imposing this kind of behaviour is extremely dangerous because one of the things that these idiots jumped on was a memo where he asked that people speculate about scenarios that could happen and backup plans if they did occur.

I personal crank theory is that Leonardo was correct about this sense organ and the fact that none can be found proves it.

I've already used it. I have a criticism but I wish to wait until I finish because there had to be a purpose the author organized it the way he did.

So far, most of what he has written, I've known instinctively but could never describe in English ASCII. I'm blessing that man's mother because he's done this work for me.

/BAH

Subtract a hundred and four for e-mail.

He who knows what just ain't so, he works in government--to hell with him!

Well, our Western intelligentsia turns out to be a net liability, rather than an asset. A cancer on society, pretty much.

Yes, and as you say, things like this are jumped on. The only useful aspect of this is that it enables me to mark anyboody who expresses outrage, *be it a world class scientist or a Nobel prize winner*, as

....

Well, just to avoid confusion, I'm assuming that this is still John Ruscio's book you're talking about. If so, then yes, his mother is a very nice woman, you would like her. And as for his wife, she's one of my favorites.

Mati Meron | "When you argue with a fool, snipped-for-privacy@cars.uchicago.edu | chances are he is doing just the same"

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.

(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:

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.

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.

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.

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.

Flywheel Energy Storage.

Flywheel Basics Tutorial.

Bob Clark

Robert Clark wrote:

Dear Robert Clark:

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

David A. Smith

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.

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