Upside down "U" shaped manometer carbon nano tube

GCNRevenger · 2004-11-20 11:02:06

Methane gas has a much much higher molecular weight, hence, it has a much lower kenetic velocity. The result of this is that the Methane will not rise as high as Hydrogen would, and you will need to space the pumps closer together, which means you will need more of them. The weight of the gas is also physically greater, which will put more load on the cable.

I am under the impression that a waveguide pipe must be made of a material that reflects RF energy. Metals do this because of an effect called banding, which will basically cause a very wide range of wavelengths to reflect, including RF energies. The sp2 carbon that CNTs are made of do not have this effect, since their bonding is of pretty uniform, and hence it will not effectively reflect RF energy.

As far as the gas "doing work = raising higher" etc etc, that is ignoring the force of gravity and the compressability of gasses. Take a minute and think on the microscale, which I know is hard for engineers to do sometimes, but it is absolutely nessesarry to understand the problem:

Gasses are not blobs of contiguous etherial matter, gasses are merely collections of molecules that are not bound to eachother and will bounce around at random, with their velocity dependant on their weight and temperature (hot hydrogen being fastest). Gasses are majority empty space under most conditions, and this explains why gasses compress but liquids and solids do not.

The nature of "pressure" is also explained, that pressure is actually the force you get when lots and lots of molecules impact against the walls of the container. If you have more molecules in a smaller volume, then more of them will hit the sides of the pipe, increasing "pressure." You can only do this so much before the pressure becomes too high and the pipe will burst.

Now, gravity affects all things made of normal matter in the universe reguardless of size, and so there is a minimum speed you must achieve reguardless of your mass in order to break free from Earth's gravity and fly straight up into space. On Earth, this is around 11,000m/s aka "escape velocity;" the problem with the pipline idea is that gas molecules don't move this fast, and infact move much slower.

As a molecule of gas moves bascially straight up, gravity will pull it back down again, and it will be trapped near the Earth. This is why our atmosphere doesn't readily leave Earth, because gravity is constantly pulling down the molecules when they try to escape, and it can do this because the maximum speed that most molecules move is much lower then escape velocity.

Now, take these two facts together, the universality of escape velocity and the compressability of gasses. You are trying to push gasses straight up a pipeline by relying on the gasses NOT compressing. That is, you are betting the farm on the gasses reaching a great height at reasonable pressures instead of being pulled back down, so you can minimize the number of pump stages needed.

In summary, it is INHERINTLY less efficent to try and push a gas straight up by it being uncompressable, instead of pushing it straight up by the impermiable wall of a tank.

John Creighton · 2004-11-20 11:18:24

As far as the gas "doing work = raising higher" etc etc, that is ignoring the force of gravity and the compressability of gasses. Take a minute and think on the microscale, which I know is hard for engineers to do sometimes, but it is absolutely nessesarry to understand the problem:
Gasses are not blobs of contiguous etherial matter, gasses are merely collections of molecules that are not bound to eachother and will bounce around at random, with their velocity dependant on their weight and temperature (hot hydrogen being fastest). Gasses are majority empty space under most conditions, and this explains why gasses compress but liquids and solids do not.

Of course we accept that the gas will get thinner due to an increased altitude. You can derive this using the principles of fluid mechanics (continuous blobs) or by appealing to the principles of statistical mechanics. You get the exact same answer and I have went though both derivation before. I do have an undergraduate degree in physics so besides advanced stuff like relativity and quantum mechanics I have a fairly good grasp. Each pump takes the weight of the gas in the section above it and transfers that force into the tension of the nanotubes. The gasses bellow the pump do not feel any of this weight. I am not saying it is practical to build such a pipeline. I am just helping Errorist work out some of the math so we can see how practical or impractical it is. By the way there is an easier way to derive the pressure by appealing to the principles of statistical mechanics. What you do is look at how a change in volume changes the energy of the system. This way you can deal with average properties instead of integrating over some distribution.

John Creighton · 2004-11-20 11:49:41

http://www.st-andrews.ac.uk/~www_pa/Sco … .html]Wave guides

This link may be somewhat helpful. Anyway by bands I assume you mean the conduction band of mettles. This is what makes it easy for electrons to flow from on atom to another. It is the inability of the mettle to support a voltage that creates the boundary conditions for a wave guide. Nano tubes are also conductive. Maybe they are not as conductive so they may not work for a wave guide. For comparisons perposes does anyone know the conductivity of nanotubes. How does that relate to the conductivity of say copper. Another interesting thing to think about is what to use for the binding agent. Is there any binding agents that are conductive. Structural considerations should also be made if the the nanotubes are woven the material should be somewhat flexible and elastic. However if the tubes are all going in the same direction and then next layer is packed into the groves of the previous layer (closet packing?) the structure should be much more ridged. The only problem with this kind of structure is there will be no chemical bonds between the nanotubes. There may be other boding forces though. To add more boding forces it could be advantages to have periodic changes in the structure. This will lower the tensile strength sum but increase the shear strength.

John Creighton · 2004-11-20 11:59:10

Hmmm. I wonder if the conductivity of carbon nanotubes depends on the direction of current flow. For structural reason the fibers will be aligned vertically but we want current to easily be able to flow around the wave guide. Granted carbon is lighter then metal so it still could be advantageous to use it for a wave guide. However that would defeat the structural advantage of the carbon nanotubes unless perhaps they where within a very conductive bonding agent (A.K.A matrix).

John Creighton · 2004-11-20 12:02:50

Other usefull information:

http://www.me.utexas.edu/~thermonet/rev … .html]3.10 Compressibility Factor

http://chemistry.jcu.edu/pchem/Compress … essibility Graphs

http://www.cepmagazine.org/pdf/030339.pdf]Working with non ideal gasses

John Creighton · 2004-11-20 12:22:29

I here some people say that nanotubs are strong enough and I here other people say they aren’t. Well clearly this depends on how much you want to taper you cable. You don’t have it the same diameter all the way up. So with current nanotubs what kind of taper are we talking about in terms of the ratio of the diameter at GSO to the diameter at earth.

John Creighton · 2004-11-20 14:06:12

More math http://pear.math.pitt.edu/Calculus2/wee … ml]Newtons law of gravitation:
F=G M1 M2/r^2
http://iparrizar.stcloudstate.edu/~juan … entripetal acceleration is given by:
Ac=V^2/r
The acceleration beyond centripetal accleleration is:
a = 9.8 m/s2,
r = 6.38 x 10^6 m, and
G = 6.67 x 10-11 m3/(kg sec2)
http://hypertextbook.com/facts/2002/Sam … 2.shtml]Me = 5.98 x 10^24 kg
w=2*pi/24 hours*(1 hour/60^2 s)= 7.272205216643040e-005 rad/s
w^2=5.288496871297023e-009 rad^2/s^2

g(h)-a_c=G Me/(r+h)-v^2/r= K Me/(r+h)-((r+h)*w)^2/r=G Me/(r+h)-(r+h)*w^2

What we should recognize is that the gravity decreases inversely with r+h so if h is equal r the gravity cuts in half. This would be after 6000 Km. The centripetal acceleration is proportional to (r+h) with the constant 5.288496871297023e-009 rad^2/s^2. This term will not significantly effect the acceleration until the gravitational forces are negligible. Without doing further math 6000 pumps sounds reasonable. I will work more on this later. If the pumps were placed 5 times as far apart then only 1200 pumps would be needed but one side of the pump would be working at 0.01 atmosheres. This would mean a much reduced flow rate.

John Creighton · 2004-11-20 14:35:38

http://www.esa.int/SPECIALS/Launchers_H … html]Types of orbits

http://www.jimloy.com/astro/moon0.htm]h … /moon0.htm

Just putting thins in perspective. Gravity starts to significantly drop around 6000 km but GSO is not untill 36 000 Km at wich point earths gravity is 1/36g. The moon is at 363,000 km from the earth.

Austin Stanley · 2004-11-20 22:08:22

All of this stuff relies upon lifting a continuous colum of water up to orbit. I think this is impracticle due to the mass involved. Assuming a tube of about 1cm^2 in cross section, the first 300 kilometers alone would mass 30 metric tons, and the entire colum up to geosynchronous orbit would weigh more than 3000 metric tons. Clearly to much for any reasonable elevator to support, regardless of what crazy system of pumps you develop to try and bring it up.

MarsDog · 2004-11-21 00:38:29

All of this stuff relies upon lifting a continuous colum of water up to orbit

Yes the pressures are too great, so you have to break it up into sections.

A diode voltage multiplier is a good electrical analogy.

Hooking up fishtank vibrator air pumps in series is a mechanical equivalent.

GCNRevenger · 2004-11-21 10:52:49

Lets see here, a little recap:

-6,000 space-rated vacuum pumps, waveguide energy "pipe," associated low hydrogen permiability pipe (probobly not made of soley of CNTs, too reactive w/ H2), valves, and the weight of the gas you are trying to lift those 36,000km. Tremendeous energy consumption, high probability of ground debries strikes in the event of cable failure with the superheavy weight cable, pipeline, and big pumps full of flammable stuff.

-Orrr you can make an elevator with multiple rails, at least two (one going up and one going down) that would probobly support an order of magnetude higher transportation rates since most of the load on the cable would be the climbers and the payloads themselves. Plus other payloads could also be sent up & down the same cable without modification.

Gee I know which one I'm gonna put my money on

John Creighton · 2004-11-21 12:45:10

So far the pipe sounds impractical because it would weigh too much. Even if that much mass could be delivered to GEO there is serious safety concerns to consider. Consider the pumps. Even if they only weighed ten pounds each 6000 pumps would weigh 60 tons. It is hard to imagine 60 tons of pumps falling from the sky. Moreover I don’t know of any 10 pound pump that can move the quantity of fluid needed. Pump are also prone to break down. At each pumping station you may want to have several backup pumps. I think you would need to develop a new kind of pump that used magneto constriction to contract and expand a tube kind of like an esophagus. With such a pump perhaps a section of gas could move up at a time rather then filling up the entire pipe. This would reduce the weight of the system some. If the system could support a gas filling the entire pipe perhaps it could also be used to move liquids but only a section at a time. Anyway more math to come to better calculate the amount of pumps needed.

GCNRevenger · 2004-11-21 12:50:56

I think that its safe to say that it will be a huge number any which way though.

I think the Russians have dabbled with such a pump, using magnets to manipulate a viscous fluid full of metal particles to squeeze a flexible hose. It would be heavy though, all those magnets and the metal-bearing fluid.

John Creighton · 2004-11-21 12:52:58

I think that its safe to say that it will be a huge number any which way though.
I think the Russians have dabbled with such a pump, using magnets to manipulate a viscous fluid full of metal particles to squeeze a flexible hose. It would be heavy though, all those magnets and the metal-bearing fluid.

I thought there was some fibers that would contract in an ellectric or magnetic field. ???

John Creighton · 2004-11-21 13:41:34

Calculation of the amount of pumps needed
As previously mentioned the additional amount of pumps needed per length is proportion to the force of gravity. We can neglect centripetal acceleration because it is to small to make much difference. I claim this can be written mathematically as:

dN/dh=(1/k)*/(P*g/rho)/ (P_o*g_o/rho_o)^2

Where:

rho is the density of the gas on the high pressure side of the pump
P is the pressure of the gas on the high pressure side of the pump
g is the force of gravity at the pump
G is the universal gravitational constant
M_E is the mass of the earth
R is the radius of the earth
r is the distance from the center of the earth
h is altitude
N is the number of pumps.
k is the number of attenuation constants between pumps. The fraction of gas remaining is given by e^(-k)
k=1 gives 0.3679, k=5 gives 0.0067, k=10 gives 4.5400e-005
k=1 seems the most practical.

From: http://www.elmhurst.edu/~chm/vchembook/ … tygas.html
http://www.ec.gc.ca/pdb/ghg/lfg_protocol_e.cfm]Methane Data
Here are some densities:
Densities of Common Elements and Compounds
(Substance Density kg/m^3)

Hydrogen gas 0.000089e3
Helium gas 0.00018e3
Air 0.00128e3
Carbon Dioxide 0.001977e3
Water 1.00e3
Methane 0.0006557e3

The calculations will be done for air. Notice that methane is lighter then air.
To find the number of pumps needed we integrate the above expression from the radius of the earth to GEO.
N=(1/k)int(P*g/rho),/(P_o*g_o/rho_o)^2, h=0…36e9)

Not that (P_o*g_o/rho_o) is the distance over which the pressure drops by 1/e.

=1000 Pa * 9.8 m/s^2/0.00128e3 kg/m^2=7.6563e+003 m for air.

In the calculation below we will use 6.92105e3 instead of 7.6563e+003 so are integral agrees exatly at the first pump wich will be at 7.6563e+003.

Which is about 7.7 km. If the pressure at the high pressure side of each side is the same the expression for N becomes

N=(1/(k*6.92105e+003))int(g/g_o, h=0…36e6)= (1/k)int(G M_E/(h+R)^2/g_o, h=0…36e6) /0.3013
= (1/k*6.92105e+003)*int(6.67e-11 * 5.98e24/h^2/9.9, h=6e6…42e6)
=(1/k)* (-6.67e-11 * 5.98e24)/(9.9*6.92105e+003)*((1/42e6)-(1/6.38e6))=1000/k

Now to get it for others we can do this trick

For hydrogen:
1000*(density of hydrogen/density of air)
= 1000*0.000089e3/0.00128e3=69.5313
For methane:
773.8850*0.0006557e3/0.00128e3=512.66

So that is 70 pumps for hydrogen, 513 pumps for methane and 1000 pumps for air. The pumps start out being spaced 7 km apart and get further apart as the altitude increases. Also note that when the pumps get further apart the tubes must get wider to keep the viscous forces the same.

John Creighton · 2004-11-21 15:42:04

70 pumps for hydrogen with 63% pressure drop between pumps. Shoot a hole in those numbers .

ERRORIST · 2004-11-21 21:15:47

John,
Don't say trick. GCN is watchcing. Since the tube diameter is 1/4 to 3/8 diameter the pump doesn't have to be that large. I suspect each one could weigh less than a 1/4 pound.They have even invented Nano pumps that are just a few microns across. Remember it does not take very much fuel to run the ion engines in space.So vast quantities are not in order.

John Creighton · 2004-11-22 08:58:21

John,
Don't say trick. GCN is watchcing. Since the tube diameter is 1/4 to 3/8 diameter the pump doesn't have to be that large. I suspect each one could weigh less than a 1/4 pound.They have even invented Nano pumps that are just a few microns across. Remember it does not take very much fuel to run the ion engines in space.So vast quantities are not in order.

We haven’t yet figured out a reasonable diameter for the tubs. For this idea to be economical it has to move much more then can be simply moved by winching tanks up a cable. Otherwise it would not make economic sense because the pipe system would weigh more. To figure out how much fuel you need to move you first need to know the weight of the system. Then you figure out how much it would cost to move this much mass into GEO. You then multiple that by a reasonable borrowing rate (say 0.1) to see how much you need to pay each year to finance it. This gives you the fixed operating cost. You could then figure out how much fuel you could get to GEO for this fixed operating cost and that will tell you need to move more fuel than that to make the system economical. Remember we haven’t considered the electric bill, insurance cost, development cost, production cost or the maintenance cost. The final thing to remember is we are only considering the economics. We must also address the safety concerns.

ERRORIST · 2004-11-22 09:19:42

I don't think any one comany would do this sort of thing it would have to be government project. Any such project is just to risky. A good example would be the Shuttle to much risk involved.

John Creighton · 2004-11-22 09:43:45

note I have some mistakes in my error analysis. Will check later. I was just trying to do it off the top of my head. Will rievew some.
http://teacher.nsrl.rochester.edu/phy_l … html]Error Analysis in calculations notice that d/dx(1/x)=-1/x^2 for error propogation in a product we are interested in (abs((error*df/dx)/f(x))=abs(error/x)

So say the number 1/6.92105e+003 had 1% error then the error it would contribute to the product would be 6.92105e+003*0.01=69.2105. Sometimes errors are added in quadrature sometimes they are just added. It depends on if you assume the errors are independent or not. Regardless an error in 1/6.92105e3 by one percent means my calculations could be off by 69.2 pumps. I think I fixed my procedure but an error analysis is worthwhile.

John Creighton · 2004-11-22 09:46:37

I don't think any one comany would do this sort of thing it would have to be government project. Any such project is just to risky. A good example would be the Shuttle to much risk involved.

That may be true but government still has to look at if it is cheaper to send the fuel up on a space elevator, pipe the fuel up to space or deliver it using an air breathing rocket. You would want them to get the most for their money wouldn’t you?

ERRORIST · 2004-11-22 09:48:42

That is true.Also,gravity doesn't win in the smoke stack example so how could it win over the longer version of the siphon example especially if gravity has less force the higher you go?
How does the math look in this case?

John Creighton · 2004-11-22 10:14:07

That is true.Also,gravity doesn't win in the smoke stack example so how could it win over the longer version of the siphon example especially if gravity has less force the higher you go?
How does the math look in this case?

Yes it does. The smoke rises untill it is no longer lighter then the air. It is lighter then the air because it is hotter but it will cool off as it rises.

ERRORIST · 2004-11-22 11:01:04

Yes, but when I open my air valve to to my unlit wood burning stove that is ice cold the air still rushes in from the bottom even when there is no wind outside. This is the natural circulation I am talking about with the two open ends at different elevations.

John Creighton · 2004-11-22 11:19:11

Yes, but when I open my air valve to to my unlit wood burning stove that is ice cold the air still rushes in from the bottom even when there is no wind outside. This is the natural circulation I am talking about with the two open ends at different elevations.

You will see circulation where there is air. There is not much air past 7 Km. There is not enough preassure on the earth to support air past that height let alone support it all the way to GSO (36 000 km).

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#26 2004-11-20 11:02:06

Re: Upside down "U" shaped manometer carbon nano tube

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Re: Upside down "U" shaped manometer carbon nano tube

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Re: Upside down "U" shaped manometer carbon nano tube

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#34 2004-11-20 22:08:22

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#35 2004-11-21 00:38:29

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#37 2004-11-21 12:45:10

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#38 2004-11-21 12:50:56

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#39 2004-11-21 12:52:58

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#41 2004-11-21 15:42:04

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#42 2004-11-21 21:15:47

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#43 2004-11-22 08:58:21

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#44 2004-11-22 09:19:42

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#45 2004-11-22 09:43:45

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#46 2004-11-22 09:46:37

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