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Pipeline To Space?

  1. Dec 27, 2004 #1
    Pipeline To Space???

    A carbon nano tube pipeline from the Equator to geo. orbit could pump massive amounts of H2 and O2 to space to be stored as rocket fuel. The pipeline would only have to be 1/4 inch diameter.

    http://www.newmars.com/cgi-bin/ikon...;f=5;t=198;st=0
     
  2. jcsd
  3. Dec 28, 2004 #2
    The link is not opening.

    Besides the cost would also be massive not to mention the different amount of weather, temperature and pressure conditions the pipeline will have to go through.
     
  4. Dec 28, 2004 #3
    Last edited: Dec 28, 2004
  5. Dec 28, 2004 #4

    russ_watters

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    "Massive" amounts of air through a 1/4" diameter pipe? No.

    Its an interesting idea, in any case, but it still doesn't deal with the fact that it can't be built with any technology we are likely to have in the forseeable future.
     
  6. Dec 28, 2004 #5
    I guess Carbon Nano Tubes are not far along yet? Perhaps, a 1/2 inch tube.
     
  7. Dec 30, 2004 #6
    Hello Errorist,
    You said:

    "A carbon nano tube pipeline from the Equator to geo. orbit could pump massive amounts of H2 and O2 to space to be stored as rocket fuel. The pipeline would only have to be 1/4 inch diameter."


    Errorist,
    WOW! If someone could develope a system that could send gases into orbit, (to be used for rocket fuel) and not send it in the traditional manner (space shuttle, etc.), that would be a huge cost saver.

    I believe you are on to something here. I wonder if H2 and/or O2 is lighter than methane (I am not very learned in science, nor the element table, etc.)?

    Anyway, perhaps methane could be used for a propulsion method for the H2 and O2 (if the methane is heavier than the H2/O2), in order to get it out to space. Being that the pipe is only 1/4" in diameter this would be helpful for connecting it to a methane propulsion system, which in turn could assist the gases into orbit.

    This should be extremely cost effective because the propulsion system would not need much in order for it to work (for example, grease or some other lubricant).

    The government would probably support this fueling method as well because it would most likely be cheaper when compared to other costly space programs of the past and present.
     
  8. Dec 30, 2004 #7
    If we're talking about elevating gases into LEO, does it matter that orbiting spacecraft are moving at thousands of kph relative to the (stationary) pipe? How do you work around that?
     
  9. Dec 30, 2004 #8

    FredGarvin

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    Gee....does anyone know where we can get a pump to overcome that head? Let's see...you have about, what...60 miles, that's 316800 ft of static head right there (assuming constant gravity which I know it's not), not to mention the pressure drop you'd encounter over the length of a Ø.250" tube, especially at a flow rate to make this all worth the while. I'll have to go and work the numbers just for kicks.
     
  10. Dec 30, 2004 #9
    Rachmaninoff,
    It would be in a Geo. orbit like the space elevator!!

    Here are some numbers worked out on the Idea. I think even more powerfull pumps could work thus lowering the number of them needed by ten fold.

    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:
    Quote
    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/123Adensitygas.html
    Methane Data
    Here are some densities:
    Densities of Common Elements and Compounds
    (Substance Density kg/m^3)
    Quote
    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.
    Quote
    =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
    Quote
    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
    Quote
    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.
     
    Last edited: Dec 30, 2004
  11. Dec 30, 2004 #10
    Pump?

    Fred said:
    "Gee....does anyone know where we can get a pump to overcome that head?"

    Every country has one (or more), all that is needed is some type of lubricant for reduction of friction.

    Methane, I believe, would be usefull as the propulsion gas since it is so readily available.

    As for the LEO spacecraft flying by too quickly, well we would have to figure out a way for the aircraft to slow down. Personally I believe methane could be used for this as well. If the space craft could be turned around, and if another mathane propulsion system is implemented, I think that in a specific matter of time that the craft could be slowed to a velicity of 0 mph.
     
  12. Jan 3, 2005 #11
    If you can build me a single carbon nano-tube 18000 miles long... then I've got some nice real estate to sell you.

    Better yet, show me a CNT just ONE mile long.

    Even better still, show me a CNT 1000 feet long.

    Sorry to burst bubbles, but there are serious hurdles to overcome before we can even build multi-mile long CNTs, let alone use them for space elevators and whatnot. I'm not saying it's never going to be done... I'm just saying don't hold you breath.

    Cheers...
     
  13. Jan 3, 2005 #12

    russ_watters

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    Actually, head wouldn't be an issue if pumping hydrogen: its lighter than air, so it'll rise through the pipe without anything more than air pressure pushing behind it.

    For flow-rate vs pressure drop, yeah, I'm guessing someone didn't consider friction inside the pipe when they came up with that 1/4" dia. I can't imagine getting useful flow out of anything less than a foot diameter pipe.

    A 12" pipe with a fairly generous pressure drop of .05" w.g. per 100 feet (I design HVAC ductwork for a living...) is good for 480 cubic feet per minute. At 22,000 miles to geostationary orbit, that's a total pressure drop of 4840' w.g. or about 2000psi.

    Now, of course, since hydrogen is compressible, pumping it at 2000psi will add a pump-head issue....

    And then, of course, is construction difficulty...

    And hey - welcome aboard: you sound like an engineer...?

    Errorist, I didn't put much effort into trying to understand that equation, but it looks suspiciously like gibberish. I don't see anything having to do with friction or flow rate, for example.
     
    Last edited: Jan 3, 2005
  14. Jan 3, 2005 #13

    FredGarvin

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    Thanks for the welcome, Russ. Nice place you got here.

    Yes. I am an engineer.

    Even if the delta P could be overcome, there's always the question of how would multiple pump stations be built at various altitudes? Pump station number 1 (on the ground) would be a piece of cake (theoretically). It's pump stations 2 and up that have me wondering...how does one build a pumping station 7 km straight up?
     
  15. Jan 3, 2005 #14
    It would be lowered from Geo.orbit from above. Just like a pump that has gone bad in a well it would have to be lowed down to the Earth from above after repairs have been made or initial installation.
     
  16. Jan 3, 2005 #15
    Through most of the 30,000 mile pipe, the hydrogen would be at a higher pressure than that of the surrounding atmosphere. That might make it be rather heavy and exert more than 14.7 PSI of pressure at the elevator base on Earth.

    And, if this is rocket fuel, why would you be pumping it as a gas instead of as a liquid?
     
  17. Jan 3, 2005 #16
    If the nano tube material can handle the stresses then a liquid could also be possible.
     
  18. Jan 3, 2005 #17
    I think we're neglecting the major issue here... CNTs cannot be made of the length you are specifying, errorist.

    Providing that they could, how many would you need to string side by side in order to build this pipe?

    Run a quick hoop stress analysis on the kind of maximum pressure you would see at any point in this pipe and you will quickly see it is a daunting task. You would need to run CNTs circumferentially around this pipe in order for it to contain even the smallest of pressures. Think of it this way, you can't build a barrel out of parallel lengths of fishing line.

    If a sky hook/space elevator type structure could be built, it would be much more economical to package the fuel on good 'ol terra firma and then run it up in tanks than to build a really, really, REALLY long pipe... especially since you wouldn't be running the pump 24/365.

    Look, I'm not saying it's impossible... it is just so impractical and uneconomical that it is almost useless.

    Cheers...
     
  19. Jan 4, 2005 #18
    The space elevator needs a really long cable. Why not make it hollow? Airplanes need wings. We make them hollow and seal them so they can serve double duty as fuel tanks.



    With the exception of shutdowns for repairs and scheduled maintenance, the Alaskan pipeline runs 24/365.
     
  20. Jan 4, 2005 #19

    FredGarvin

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    That doesn't make a whole lot of sense to me. If I am understanding this correctly, you're saying that the tube would also not only have to support itself and withstand any loads imposed on it by the environment, but it would also have to support the pumps, valving and services as well? Also, it would be flexible to winch in and out from space?

    Honestly, it's a good brainstorming session to try to alleviate the issues with the expense of Earth based launches, but it is anything but realistic. We haven't even begun to discuss what the environmental folks would have to say about having a huge pipeline dangling through the atmosphere.
     
  21. Jan 4, 2005 #20

    russ_watters

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    Yes, it was a developing idea and didn't go back and rewrite the beginning when I reached a different conclusion at the end (I think its useful to show the whole thought process).
    Well, I was going to let that go before, but now errorist brought it up...

    Sending up liquid hydrogen would compound the problems exponentially (as if they aren't already daunting enough?) - first, how do you keep it a liquid in a 22,000 mile pipe? Second, its now much, much denser and requires a pipe several orders of magnitude stronger than if you're sending up a gas.
    Airplanes have to carry their own fuel, otherwise they couldn't fly - its not the same thing. It would indeed be more efficient to carry liquid or gas up the elevator of a building (for example) than to pump it. And it just so happens that the same reasons you wouldn't do that in a building are the reasons you would do that with a space elevator: Pressure issues, heat (cryogenics), and efficiency.

    But this is all still useless speculation: we're discussing how you would use something that can't be built! :rolleyes:
     
    Last edited: Jan 4, 2005
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