Thread: Space elevator

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  1. #21
    Titan Adam Jensen's Avatar
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    Quote Originally Posted by Reeve View Post
    Yes, cable is very heavy, but this cable would be made from Carbon nanotubes, which are relatively light, and the farther away from Earth they got, the lighter they would get, due to the lower force exerted by Earth's gravity. At some point, the centripetal force of the counterweight pulling on the cable should be stronger than the pull of Earth's gravity, and then remain much stronger for the remainder of the distance to that counterweight. Now, whether you could build a system to hitch it to on that counterweight and on Earth that would be able to support those stresses, I don't really know.

    Edit: I don't really know that much on this, and I'm totally armchair speculating. But I think it's good to speculate and let people like McSpriest who know something about structural engineering explain why it doesn't work.
    Even if its nano-tubes, to go as high as the spaceshuttle went, that's 400 miles of cable (two hundred to go up, and two hundred coming back down.)

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  2. #22
    You watch to much Gundam ;D

  3. #23
    Stood in the Fire McSpriest's Avatar
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    Quote Originally Posted by Reeve View Post
    Yes, cable is very heavy, but this cable would be made from Carbon nanotubes, which are relatively light, and the farther away from Earth they got, the lighter they would get, due to the lower force exerted by Earth's gravity. At some point, the centripetal force of the counterweight pulling on the cable should be stronger than the pull of Earth's gravity, and then remain much stronger for the remainder of the distance to that counterweight. Now, whether you could build a system to hitch it to on that counterweight and on Earth that would be able to support those stresses, I don't really know.

    Edit: I don't really know that much on this, and I'm totally armchair speculating. But I think it's good to speculate and let people like McSpriest who know something about structural engineering explain why it doesn't work.
    i actually was very interested in carbon nanno tubes since 2005. the are extremely light, but at a distance of about 22,000 miles even they are heavy. 22,000 miles of feathers is heavy. and although structural technology is advancing. the point remains that the structure required for something like this would be VERY costly. to the point that it would be far cheaper to launch a space shuttle every time. the numbers are very high and i'm sure i could calculate them if i really had to but rest assured that the gravitational forces generated would make this not possible. the wikipedia article on this actually explains the theory of using centrifugal force of the earth's rotation to cause it to be an upward tensile force. in this case its going to be large force exerted on the ground and would require massive anchors. i'm not so sure this wouldn't affect earth's orbit.

    Wikipedia article
    Last edited by McSpriest; 2012-02-29 at 05:40 PM. Reason: physics talk getting to convoluted

  4. #24
    Legendary! Sorrior's Avatar
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    Quote Originally Posted by Himora View Post
    You watch to much Gundam ;D
    You watch too little. Only ONE gundam series has EVER used space elevators and that's 00(AGE is on the fence seeing as we haven't seen earth yet) and even then the idea is FAR older than Gundam 00.

    Oh and you want crazy talk from gundam? How about we turn giant pueces of the earth into orbiting space colonies?


    But more seriously. I see no problems with someday building a space elevator provided we last another 100-200 years the tech required would probably be so standard and cheap it's be like setting up a highseed train today. Give us 500 years and privided we don't blow ourselves up OR thrust ourselves back to the dark ages all the tech required would probably be borderline science fair tech. Then if we double that to 1,000 years ummm yeah by then freaking infants will probably be playing with more advancedtech than this calls for.

  5. #25
    The Insane Reeve's Avatar
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    Quote Originally Posted by McSpriest View Post
    i actually was very interested in carbon nanno tubes since 2005. the are extremely light, but at a distance of about 22,000 miles even they are heavy. 22,000 miles of feathers is heavy. and although structural technology is advancing. the point remains that the structure required for something like this would be VERY costly. to the point that it would be far cheaper to launch a space shuttle every time. the numbers are very high and i'm sure i could calculate them if i really had to but rest assured that the gravitational forces generated would make this not possible. the wikipedia article on this actually explains the theory of using centrifugal force of the earth's rotation to cause it to be an upward tensile force. in this case its going to be large force exerted on the ground and would require massive anchors. i'm not so sure this wouldn't affect earth's orbit.

    Wikipedia article
    Right, the centrifugal force would theoretically generate enough upwards pull on the cable to keep it aloft. The weight of the cable would be great close to Earth, but keep in mind that the acceleration due to gravity would reduce the farther it gets from Earth. I'm not sure how far out you have to be to get to 1/4 Earth's gravity, for example, but I'll bet it's a lot less than the 60,000 miles the company in question is citing.

    Again, I think the company in question is citing a pipe dream. I just like to think about how maybe it could be possible.
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  6. #26
    Just wondering, what are the uses for a space elevator?

    Also, they intend to start building it in 2050? Fuck, I might be able to see that !

  7. #27
    how much would it cost to make that cables anyway ?

    i mean for the sake of humanity, manifacturers could do it for cheapest price.

  8. #28
    Stood in the Fire McSpriest's Avatar
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    Quote Originally Posted by Reeve View Post
    Right, the centrifugal force would theoretically generate enough upwards pull on the cable to keep it aloft. The weight of the cable would be great close to Earth, but keep in mind that the acceleration due to gravity would reduce the farther it gets from Earth. I'm not sure how far out you have to be to get to 1/4 Earth's gravity, for example, but I'll bet it's a lot less than the 60,000 miles the company in question is citing.

    Again, I think the company in question is citing a pipe dream. I just like to think about how maybe it could be possible.
    from a purely physics thought experiment point of view it IS possible, yet from a realistic factors point of view the forces generated in this would far exceed the limitations of any material and while carbon nanotubes are a step in that direction. you are going to run into the problem that any material used would need a tensile strength that would exceed it's weight per mile over 22,000 miles. and its going to have to carry that weight in full because the design calls for placing all the weight as tensile force by using the earths rotation. i'll do math now

    mass of carbon nanotube is about .007839 pounds per inch or about 10,927,828.26 pounds over a 22,000 mile length double that since it needs to come back too so 21,855,656.52 pounds

    the maximum tensile strength of the best carbon nanotube ever made was about 100GPa which converts to 14,503,773.773 psi
    thats at breaking point, yet the tubes start plastic deformation at 5% of maximum tensile strength. meaning the maximum safe threshhold is about 725,188.689 psi far under the required 21,855,656.52 pounds required

    also as a side note the longest length of nanotube ever created was made in 2009 at a length of 18.5 cm or 7.283 inches... a long way to go to create what would be a 45,000mile length of tube. and as for weaving multiple tubes together, that would detract from the strength of the material and while possible it would mean being even STRONGER to compensate
    Last edited by McSpriest; 2012-02-29 at 06:23 PM.

  9. #29
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    Capitalism and human greed, why we can't have nice things since forever.

    I would sell my soul for one of those space elevators. >.>

  10. #30
    Sounds ridiculous - how's the cable to hold, up at the top, that much length of it + the elevator itself? The weight would be immense! o.O

    Plus I wouldn't trust such a structure - the movement of the earth would cause a lot of sway wouldn't it ? Wouldn't want to be in the elevator when it "snaps" D:
    Last edited by BeerWolf; 2012-02-29 at 06:37 PM.

  11. #31
    The courage to do the impossible lies in the hearts of man. I'm glad somebody out there isn't afraid to attempt something huge.

  12. #32
    Quote Originally Posted by McSpriest View Post
    no its not the ability to lift itself that is the problem its that you wouldn't be able to keep that much weight aloft. as in the weight is so massive there is no way it wouldn't all fall back to earth the force of gravity pulling down would require the mother of all gears and mechanical rooms at the top. it would rip through anything tis attached to.
    Attach the other end to the moon. The cable won't be as heavy as the moon, so the moon won't get pulled to the earth.

    (This is a joke.)

  13. #33
    Mechagnome Taters91's Avatar
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    Being in a lift for 180 Hours?! O__o I'll think I'll pass on that one! :S

  14. #34
    I have always wondered why they have to fire shuttles up attached to enormnous amounts of volatile fuel. These space flights Branson and co were meant to be setting up, why not attach a shuttle to the under carriage of one of them and once near the thin blue line, shuttle disengages and nose up into space. Someone explain to me why this can't happen.

    OR

    WHy not take off from land and keep circling up

  15. #35
    LOAD"*",8,1 Fuzzzie's Avatar
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    It sounds like a great idea, then again, one terrorist attack or mistake and there's 80KM of elevator crashing down all over earth.

  16. #36
    The Insane Reeve's Avatar
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    Quote Originally Posted by McSpriest View Post
    from a purely physics thought experiment point of view it IS possible, yet from a realistic factors point of view the forces generated in this would far exceed the limitations of any material and while carbon nanotubes are a step in that direction. you are going to run into the problem that any material used would need a tensile strength that would exceed it's weight per mile over 22,000 miles. and its going to have to carry that weight in full because the design calls for placing all the weight as tensile force by using the earths rotation. i'll do math now

    mass of carbon nanotube is about .007839 pounds per inch or about 10,927,828.26 pounds over a 22,000 mile length double that since it needs to come back too so 21,855,656.52 pounds

    the maximum tensile strength of the best carbon nanotube ever made was about 100GPa which converts to 14,503,773.773 psi
    thats at breaking point, yet the tubes start plastic deformation at 5% of maximum tensile strength. meaning the maximum safe threshhold is about 725,188.689 psi far under the required 21,855,656.52 pounds required

    also as a side note the longest length of nanotube ever created was made in 2009 at a length of 18.5 cm or 7.283 inches... a long way to go to create what would be a 45,000mile length of tube. and as for weaving multiple tubes together, that would detract from the strength of the material and while possible it would mean being even STRONGER to compensate
    Well the weight of those nanotubes isn't constant along the whole length of the cable. The weight reduces the farther you get from Earth's center. That said, your point is pretty solid, and I'm feeling like it's unlikely nanotubes in their current form could withstand that sort of stress.

    That said, I think it's always possible we could figure out how to make it better. Perhaps certain weaves are stronger per pound than the fibers would be themselves? I don't really know. I still think it's worth thinking about and trying to figure out ways around the problems.
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  17. #37
    Legendary! Sorrior's Avatar
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    Quote Originally Posted by Fuzzzie View Post
    It sounds like a great idea, then again, one terrorist attack or mistake and there's 80KM of elevator crashing down all over earth.
    See gundam 00 it happens and the death toll was insane and woulda been worse if not for in series reasons.


    Oh and what about orbital elevator ring hybrids(yes ala Gundam 00 and Tekkaman Blade). Basically multiple elevators with an orbital ring essentially supporting each other?

  18. #38
    LOAD"*",8,1 Fuzzzie's Avatar
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    Quote Originally Posted by Sorrior View Post
    See gundam 00 it happens and the death toll was insane and woulda been worse if not for in series reasons.
    idk, do you have a clip? It's gonna be tough for me to sit through all that just for a scene

  19. #39
    It's an interesting idea, but I don't see the point of building it. (At the present time at lest)

  20. #40
    Epic! Sayl's Avatar
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    While the space elevator is a nifty concept, we'd need a serious change in policy and priorities in order to do anything with one (and by we I mean the world's space agencies, hopefully working together instead of competing). Looking to the future is indeed important. It just seems close to pie-in-the-sky at a time when the US space program doesn't even have a heavy-lift launch vehicle.

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