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The larger the cloud of gas, the longer it will take... it wouldn't stay indefinatly wind or no.
[i]"The power of accurate observation is often called cynicism by those that do not have it." - George Bernard Shaw[/i]
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Suppose you vacuum out the tube, and place an Ion engine at the bottom, and give the tube a stronger same charge as the ion engine? This way the ions never touch the tube but are accelerated very fast past escape velocity
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Again, an ion engine cannot ionize any useful quantity of hydrogen and would have too high an energy requirement. You have to be able to move many kilograms of hydrogen per day, and no ion drive even comes close to this considering the energy required per-mass of hydrogen.
[i]"The power of accurate observation is often called cynicism by those that do not have it." - George Bernard Shaw[/i]
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That is because they are designed to be very fuel efficient. They have a variable thrust mode. They can be designed to use a very high fuel consumption rate.
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This does not overcome:
~The fact they must be run at escape velocity efficencies, which is still pretty high per-mass.
~You must move a VERY large number of molecules, since each individual molecule of hydrogen weighs so little. Xenon, typical ion engine fuel, weighs 66 times as much.
~This does not mitigate the energy required to ionize the hydrogen in the first place, which is extremely energy intensive for a given mass, with the large number of molecules involved.
~You are still going to need one that is so big, its almost comical to move many kilograms per day. Capturing the gas on the other end may be problematic too given its very high velocity and electric charge.
Nope, won't work either.
[i]"The power of accurate observation is often called cynicism by those that do not have it." - George Bernard Shaw[/i]
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If you can get the ions up to just escape velocity then it won't use as much energy as the spacecrafts. They accelerate the ions up to 250,000 meters per second.To reach the station you only need 24,000 Mph. So not as much enregy is needed but you need more grams per hour so it may just may equal out. The ion engines use about 20 grams per hour thrust. The ones we could use or build on land could be many pounds per hour.BTW in theory any gas could be used for ion propulsion.
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Any gas can be used, if you can ionize it. Because hydrogen weighs very little per mole, and it has a hydrogen-hydrogen bond you have to break, its ionization energy is many, many times that of Xenon. This is where the majority of the energy is consumed, not with accelerating the resultant particles.
Lets say for a minute that you can ionize and propel the hydrogen atom just as easily as a Xenon atom, even though you can't, and the "engine" were 100 times as big... since hydrogen atoms weigh 132 times less than Xenon atoms each, then you can push about 15g a day...
In one whole year, you pushed a grand total of 12.2 pounds of hydrogen to orbit!... and you would lose that much to leaks and boiloff anyway. Even two orders of magnetude improvement over this figure is still a measly half ton over a whole year of continuous operation.
[i]"The power of accurate observation is often called cynicism by those that do not have it." - George Bernard Shaw[/i]
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Ok lets use Xenon,Neon or He.
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Helium has similar issues, and is even harder to ionize... you'd be lucky to get ten pounds a year.
As far as the others go, why? They are heavy and make lousy rocket fuel, and are only good for ion engines which are really, really slow. Since ion engines are so efficent, it isn't worth it to build a multibillion dollar pipeline to space when you can just ship up a few tons on a rocket. With Xenon and this same arrangement, you could lift about 1,600lbs a year... the DC-Y was planned to haul 18,000lbs a week, and the modern Delta-IV rockets can haul several times that for a hundred million or two pop.
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I think it would be less than a billion since the mass of the pipe line is 50 times smaller than the space elevator concept. How much would it cost to send the xenon up in this manner? How much did the delta rocket program cost?
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The pipeline? Under a billion? Hardly... the ion generator of that size alone would cost that much or more. And don't forget that you need an elevator to attach it to, unless you intend to make your pipe 24,000mi long instead of 200mi. Then you have to take into account the mass of the charge guide wires which you included to ensure the cations won't interact with the walls of the tube. And then there is the fact that the tube is harder to make and more brittle than the elevator ribbon concept... and don't forget the trouble of building the pumping facility... oh the vast, vast amounts of electricity it would consume... and this isn't counting the station/counterweight on the other end
Shal I go on? Instead, invest the money into building a working DC-X reuseable SSTO rocket, or a working Scramjet X-30/NASP SSTO airplane.
Oh, and I should also add, that there isn't that much Xenon on Earth to begin with... perhaps less than a thousand tons.
[i]"The power of accurate observation is often called cynicism by those that do not have it." - George Bernard Shaw[/i]
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How about if they used Neon, and how many megawatts would it use?
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Still makes lousy rocket fuel, since its heavy, and makes lousy ion fuel since its too light nor does it ionize as easily. It would take more energy to ionize than Xenon, but probably less than Hydrogen. Depends on the method of ionization used.
Edit: Oh and its pretty dang hard to liquify too... you'd need energy for that as well, and this time you'd need it at the TOP of the tube.
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How many megawatts are you talking about?
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This question is more complicated than you know... Energies required to accomplish what you are talking about:
~First ionization energy of Neon (or other monoatomic gas)
~Bond energy of gas involved (if polyatomic)
~Energy required to accelerate multiple kilogram quantities to high enough speed to reach 400km
~Energy required for final deceleration at the top of the tube
~Energy required to compress & liquify the vanishingly low pressure gas at the top of the tube (signifigant energy required here due to low pressure)
~Energy required to create an electric field around the inside of the tube to protect it from particle collision
This is an engineering problem worthy of a doctoral thesis... I can only answer you the first two or three with my chemistry background.
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Is it in the megawatt range or tens of meagawatt range or less?
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My instinct would be in the upper end of your range, but this is a question that doesn't have quick answer. I do know that the first ionization energy of Neon, the least useful of the fuels, is 2080 kilojoules per mole. Since a mole only weighs 20.17 grams, thats quite a bit of energy just to ionize a kilogram of it.
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How about Argon?
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Only marginally better, 1500kJ/mol, and is also hard to liquify
Go here:
[http://www.webelements.com]http://www.webelements.com
Select the atom of your choice, then select ionization energies from the column on the left. Don't forget about bond energy for polyatomic molecules.
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Nitrogen doesn't look to bad. Looks safe also.
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Too heavy to make good fuel in any type of engine and has extreme bond energy with its double-sp2 pi bonding along with the regular sp3 sigma bonding.
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Mercury?
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Very high mass, hard to move. Toxic too, may cause corrosion.
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Hard to move but good for spacecraft reaction. Toxic yes but not when handled carefully. Will it corrode carbon? Low ionization.
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Elemental mercury is also in the alotrope of Hg2, that is its a diatomic molecule. The bond energy between Mercury atoms is pretty strong though.
A thermal engine needs light weight fuel, and a fuel thats too heavy will cut into the thrust of an ion engine too much.
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