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Thread: Dangling a rope from orbit.... (Is this a stupid question?)

  1. #61

    Two really good articles out in the news
    Aug12 2002 about Nasa/Space elevators

    http://news.bbc.co.uk/2/hi/technology/2188107.stm

    http://popularmechanics.com/science/...up/print.phtml

  2. #62
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    Now they have had their meeting, here is the report;

    Going Up? Private Group Begins Work on Space Elevator

    Phobos

  3. #63
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    On 2002-08-19 16:40, Phobos wrote:
    Now they have had their meeting, here is the report;
    I loved Arthur C Clarke's comment [img]/phpBB/images/smiles/icon_smile.gif[/img]

  4. #64
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    hypothetical rope

    Quote Originally Posted by sadprince View Post
    As a kid, I always wondered why "if you had the space shuttle already in orbit why couldn't you dangle a rope down and pull up supplies....(or even another person)?"

    Answering my own question years later,
    three obvious things occur to me.
    1. A normal rope would snap under its own weight.
    2. It would pull the object out of orbit.(?)
    3. Logistically, it would be very hard to control(weather/wind etc).

    Hypothesising on a solution:
    Create a rope that is of very little mass and almost infinitely strong, and assuming we can deal with (3) above by only using the rope in the right conditions, does my childhood concept have any plausibility at all?

    I have some very long rope NASA can borrow if they want to give it a go... Comments and solutions please...?????
    but the only weight the rope would have is the part within the atmosphere because the part in space would be weightless... no?
    The other two assumptions carry more weight. lol

  5. #65
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    Quote Originally Posted by nitram22 View Post
    but the only weight the rope would have is the part within the atmosphere because the part in space would be weightless... no?
    ...
    No, The atmosphere does not cause the transmission of gravity. Look for example at the Moon, which has practically no atmosphere, and yet it does have gravity (1/6th the gravity we experience on the Earth's surface) Things in orbit are weightless because they are falling in a long arc that goes around the planet. If the ISS could be made to hover over one spot on earth, the people inside it would feel almost 1G of gravity.
    Forming opinions as we speak

  6. #66
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    Since the main discussion here back in 2002, we've had the invention of graphene.

    Graphene tensile strength-to-weight ratio is orders of magnitude greater than anything else.

    130,000 Mpa, for comparison the best steel is 2693 Mpa. Plus the steel is about 8 times denser.

    In Arthur C Clarke's novel on the space elevator, I think he used some kind of diamond fibre.

    According to Wikipedia the tensile strength-to-weight ratio of graphene is about 13 times that of diamond.

    So my question is, is graphene some kind of game changer for the space elevator concept? Does it make it theoretically possible?

    https://en.wikipedia.org/wiki/Ultimate_tensile_strength

  7. #67
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    Iím guessing this, and somebody might have said it, but I think that the drag of the part of the cable in thee atmosphere would drag the shuttle into the ground.


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    As above, so below

  8. #68
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    Quote Originally Posted by kzb View Post
    Since the main discussion here back in 2002, we've had the invention of graphene.

    Graphene tensile strength-to-weight ratio is orders of magnitude greater than anything else.

    130,000 Mpa, for comparison the best steel is 2693 Mpa. Plus the steel is about 8 times denser.

    In Arthur C Clarke's novel on the space elevator, I think he used some kind of diamond fibre.

    According to Wikipedia the tensile strength-to-weight ratio of graphene is about 13 times that of diamond.

    So my question is, is graphene some kind of game changer for the space elevator concept? Does it make it theoretically possible?

    https://en.wikipedia.org/wiki/Ultimate_tensile_strength
    It's always been theoretically possible, but conventional materials required a huge taper from orbit to ground in order to support their own weight, rendering the thing impractical. The stronger the material, the less the required taper. In 2002, in The Space Elevator, Bradley Edwards was already talking about "graphite whiskers" as the potential answer; by 2006, in Leaving the Planet by Space Elevator, attention had moved to carbon nanotubes. So there's long been a perception that something based on the C-C bond was going to afford a potential solution, if only we could make molecules of it thousands of miles long.

    Grant Hutchison
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  9. #69
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    Quote Originally Posted by Jens View Post
    I’m guessing this, and somebody might have said it, but I think that the drag of the part of the cable in thee atmosphere would drag the shuttle into the ground.
    For a "conventional" geosynchronous space elevator with a ground anchor, atmospheric drag stresses the structure but doesn't affect the orbit. For the "rotovator" concepts, in a lower orbit and rotating so as to dip the tether in and out of the atmosphere, atmospheric drag is a factor requiring station-keeping, but not as much as you might expect, since the movement in-atmosphere is almost vertical.

    Grant Hutchison
    Blog

    Note:
    During life, we all develop attitudes and strategies to make our interactions with others more pleasant and useful. If I mention mine here, those comments can apply only to myself, my experiences and my situation. Such remarks cannot and should not be construed as dismissing, denigrating, devaluing or criticizing any different attitudes and strategies that other people have evolved as a result of their different situation and different experiences.

  10. #70
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    But surely a space shuttle (if there were such a thing) is going about 17,000 mph relative to the atmosphere? So if it dropped a long tether the drag would be enormous.

    The space elevator concepts I read about were dropped from geostationary orbit. So the only drag is from the weather.

  11. #71
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    Quote Originally Posted by kzb View Post
    But surely a space shuttle (if there were such a thing) is going about 17,000 mph relative to the atmosphere? So if it dropped a long tether the drag would be enormous.

    The space elevator concepts I read about were dropped from geostationary orbit. So the only drag is from the weather.
    Yes. The discussion on this thread shifted to space elevators and "rotovator" type tethers on page 2. I'm guessing you and Jens are still thinking about the 2002 OP?

    Grant Hutchison
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    Note:
    During life, we all develop attitudes and strategies to make our interactions with others more pleasant and useful. If I mention mine here, those comments can apply only to myself, my experiences and my situation. Such remarks cannot and should not be construed as dismissing, denigrating, devaluing or criticizing any different attitudes and strategies that other people have evolved as a result of their different situation and different experiences.

  12. #72
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    Other problems.
    The constant zone of thunderstorms--the ITCZ--will be near the base of any space elevator on Earth. Icing loads, lightning--maybe even discharging the global electrical circuit? Who knows?

  13. #73
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    Quote Originally Posted by grant hutchison View Post
    Yes. The discussion on this thread shifted to space elevators and "rotovator" type tethers on page 2. I'm guessing you and Jens are still thinking about the 2002 OP?
    Yes, more or less. I was responding to post 64, where the person quoted the (I guess OP) and gave a response to it. I guess that wasn't completely clear.
    As above, so below

  14. #74
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    Quote Originally Posted by publiusr View Post
    Other problems.
    The constant zone of thunderstorms--the ITCZ--will be near the base of any space elevator on Earth. Icing loads, lightning--maybe even discharging the global electrical circuit? Who knows?
    Back in 2002 Kucharek (in this thread) gave one possible answer to this. Rather than extending the elevator all the way to the ground, build a 20km high tower and attach the cable to that. A 20km tower would presumably be robust enough to withstand the weather on Earth, although the tallest structures we can build at the moment are in the one kilometre range.

  15. #75
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    Quote Originally Posted by eburacum45 View Post
    Back in 2002 Kucharek (in this thread) gave one possible answer to this. Rather than extending the elevator all the way to the ground, build a 20km high tower and attach the cable to that. A 20km tower would presumably be robust enough to withstand the weather on Earth, although the tallest structures we can build at the moment are in the one kilometre range.
    Seems at least like a possibility. And if a 20 km tower seems to difficult to build, you're likely not ready to construct a 36,000 km space elevator.
    Conserve energy. Commute with the Hamiltonian.

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