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  1. Standard member sonhouse
    Fast and Curious
    24 Jan '09 13:04 / 1 edit
    The title space does not allow a whole lot in the way of explanation:
    coming out of the labs now are carbon nanotubes that are not yet totally up to full potential strength but they are making enough to wind up 18 miles a day of the stuff now in one length, making the space elevator concept a whole lot closer! :
    http://www.physorg.com/news151938445.html

    If you look at the comments, at the end of them I made one about a concern of mine with the counterweight of the theoretical elevator, there is the station at geosync orbit but needing a counterweight a hundred thousand miles beyond that where the pull on the tether will be AWAY from the earth. I worry about how the two would be kept in a more or less straight line, how would they do that since an object orbiting a hundred thousand miles up has a natural orbital period a lot longer than one in 24 hour (by definition, geosync) orbit.
  2. 30 Jan '09 10:35
    Originally posted by sonhouse
    The title space does not allow a whole lot in the way of explanation:
    coming out of the labs now are carbon nanotubes that are not yet totally up to full potential strength but they are making enough to wind up 18 miles a day of the stuff now in one length, making the space elevator concept a whole lot closer! :
    http://www.physorg.com/news151938445.html
    ...[text shortened]... up has a natural orbital period a lot longer than one in 24 hour (by definition, geosync) orbit.
    …If you look at the comments, at the end of them I made one about a concern of mine with the counterweight of the theoretical elevator, there is the station at geosync orbit but needing a counterweight a hundred thousand miles beyond that where the pull on the tether will be AWAY from the earth. I worry about how the two would be kept in a more or less straight line, how would they do that since an object orbiting a hundred thousand miles up has a natural orbital period a lot longer than one in 24 hour (by definition, geosync) orbit.
    ...…


    I vaguely remember reading somewhere that all this has been worked out in theory with no problems.

    But my main concern is what would happen if a piece of space junk or a meteor hit the cable in space and snapped it!!! That would be a total and very expensive disaster with no chance to fix it!!! Given the amount of space junk and space rocks floating chaotically in space, his is surely a very real and obvious danger! -and, because of the mathematicians of probability, it surely would eventually happen given the space elevator being in space for long enough! -and yet I am horrified to see this obvious danger has not been even given even a brief mention in any of the literature I have read about the space elevator! -perhaps those that support this idea of making a space elevator are burying their heads into the sand on this?
  3. 30 Jan '09 12:06
    Originally posted by Andrew Hamilton
    I vaguely remember reading somewhere that all this has been worked out in theory with no problems.
    Ignore the station in geostationary orbit. The cable will drag the counter weight because the counterweights natural inclination is to be in a slower than geostationary orbit.
    All that remains is to place the space station in geostationary orbit somewhere near the cable.
    Though an alternative configuration would be to use the space station as the counter weight - the problem being that it is then harder to launch geostationary satellites from the space station.


    But my main concern is what would happen if a piece of space junk or a meteor hit the cable in space and snapped it!!!
    The solution is to not use a single cable. You either use a rope like cable or several parallel cables. I believe that all space junk down to a few centimeters in size is tracked, it is the micro space junk that is a problem.
  4. 30 Jan '09 13:01
    Originally posted by twhitehead
    Ignore the station in geostationary orbit. The cable will drag the counter weight because the counterweights natural inclination is to be in a slower than geostationary orbit.
    All that remains is to place the space station in geostationary orbit somewhere near the cable.
    Though an alternative configuration would be to use the space station as the counte ...[text shortened]... junk down to a few centimeters in size is tracked, it is the micro space junk that is a problem.
    …The solution is to not use a single cable. You either use a rope like cable or several parallel cables....…

    I agree with the latter; it would have to be several parallel cables with sufficient distance between them so that even a relatively large piece of space junk/rock cannot credibly simultaneously collide into all of them thus only one or two can be credibly snapped which hopefully will not be enough to bring the whole structure down!

    ….I believe that all space junk down to a few centimetres in size is tracked
    ….


    I am curious to know how? -I mean, if a large piece of space junk/rock is detected to be in collision coarse with the cables, what practical means would there be put in place to deflect it?
  5. 30 Jan '09 13:57
    Isn't this nanotube based on carbon? Isn't carbon sensitive to ultraviolet light, and charged particles?
    What about low (or high) temperatures? Wouldn't then carbon based nanotubes be ver vulnerable?
  6. 30 Jan '09 14:26
    Originally posted by FabianFnas
    Isn't this nanotube based on carbon? Isn't carbon sensitive to ultraviolet light, and charged particles?
    What about low (or high) temperatures? Wouldn't then carbon based nanotubes be ver vulnerable?
    Elements do not really have specific characteristics such as sensitivity to light. It is chemical compounds that do. Many elements form only one typical compound when in a pure state but Carbon is capable of many including Diamond, nano-tubes, graphite coal and others. If diamonds were sensitive to ultraviolet light they would not be so popular.
    Nano-tubes are extremely strong because they are in a very stable configuration similar to diamond and they are I believe very chemically stable too.
  7. 30 Jan '09 14:31
    Originally posted by twhitehead
    Elements do not really have specific characteristics such as sensitivity to light. It is chemical compounds that do. Many elements form only one typical compound when in a pure state but Carbon is capable of many including Diamond, nano-tubes, graphite coal and others. If diamonds were sensitive to ultraviolet light they would not be so popular.
    Nano-tub ...[text shortened]... very stable configuration similar to diamond and they are I believe very chemically stable too.
    (Diamonds are sensitive to heat, the catch fire. Try your family jewels with a match. If they don't catch fire, they're not real diamonds. Zirconium doesn't catch fire.)

    A space elevator cabel made of nanotubes is exposed to temperatures down to 100 centigrades below, heat, upt to 100 degrees plus, vacuum, UV light, charged particles, and all this under a long time, at the same time it is in very high tension.

    Do we have any links to answer the question above somewhere?
  8. Standard member sonhouse
    Fast and Curious
    30 Jan '09 17:28
    Originally posted by FabianFnas
    (Diamonds are sensitive to heat, the catch fire. Try your family jewels with a match. If they don't catch fire, they're not real diamonds. Zirconium doesn't catch fire.)

    A space elevator cabel made of nanotubes is exposed to temperatures down to 100 centigrades below, heat, upt to 100 degrees plus, vacuum, UV light, charged particles, and all this unde ...[text shortened]... e it is in very high tension.

    Do we have any links to answer the question above somewhere?
    That sounds like it could be an element in a science fiction story: We find a planet of intelligent beings where diamonds are as common as coal is here and they use it the same way, to feed to a furnace to heat their houses, we set up a deal to show them how coal is a superior fuel and we start trading. How bout that
  9. Standard member sonhouse
    Fast and Curious
    30 Jan '09 17:35
    Originally posted by twhitehead
    Ignore the station in geostationary orbit. The cable will drag the counter weight because the counterweights natural inclination is to be in a slower than geostationary orbit.
    All that remains is to place the space station in geostationary orbit somewhere near the cable.
    Though an alternative configuration would be to use the space station as the counte ...[text shortened]... junk down to a few centimeters in size is tracked, it is the micro space junk that is a problem.
    Clearly you use multiple cables and besides, the base would be movable to avoid bigger meteors and such and aircraft but you can bet there would be massive defenses set up to counter terrorist activity. I still want to know how they would just keep the counterweight from drifting back enough so the cable just impacts the atmosphere. Word here is 'it's all been worked out" but just how would they go about it? It would seem to me the only solution would be to have a powered counterweight that would have enough thrust somehow to keep a straight line. If not that then exactly how do they think they would go about it? Don't forget, they are talking about a 160,000 Km length of cable PAST the geosync point. That's almost halfway to the moon! So you can see my point, the cable could just wrap itself up and easily impact the atmosphere like a thread winding on a bobbin.
  10. 31 Jan '09 18:28
    I have always been skeptical about the space elevator and the nanotubes are made of carbon. Doesn't carbon conduct electricity?

    If so, wouldn't the ionosphere send one of the biggest lightning strikes ever to the earth and destroy the elevator before it could even be used?
  11. 31 Jan '09 18:57
    Originally posted by sonhouse
    Clearly you use multiple cables and besides, the base would be movable to avoid bigger meteors and such and aircraft but you can bet there would be massive defenses set up to counter terrorist activity. I still want to know how they would just keep the counterweight from drifting back enough so the cable just impacts the atmosphere. Word here is 'it's all b ...[text shortened]... uld just wrap itself up and easily impact the atmosphere like a thread winding on a bobbin.
    …the base would be movable to avoid bigger meteors
    .…


    I think that would be easier said than done simply because of the massive extra expense of making a movable base which I would guess would have to way thousands or even hundreds of thousands of tons else it would simply takeoff due to the massive upward pull of the cable! And the machines that have to move such a heavy base and while the cable it tagging at it would have to be extremely powerful! (and therefore expensive).

    I think the whole idea of a space elevator has so many serious technical problems that it would be simply a technical nightmare to implement and not worth thinking about at least in our life times -perhaps in ~200 years time?
  12. 31 Jan '09 19:09 / 2 edits
    Originally posted by Metal Brain
    I have always been skeptical about the space elevator and the nanotubes are made of carbon. Doesn't carbon conduct electricity?

    If so, wouldn't the ionosphere send one of the biggest lightning strikes ever to the earth and destroy the elevator before it could even be used?
    I had thought about exactly the same thing but I don’t know enough about physics to do the calculations to see if such a danger is credible.
    But carbon in the form of nanotubes DOES conduct electricity!

    -and this is not to mention the danger of the cable being struck by ordinary lighting from a thunder storm! -could that overheat the cable until it weakens enough to snap? -or even set the cable on fire!? -even carbon in the form of relatively heat resistant nanotubes is not completely fire resistant!

    And what if a tornado strikes it and throws something heavy into it at high velocity?
    Or could strong winds cause it to resonate or oscillate at a distractive frequency? (this phenomenon has already brought down a few bridges).

    And what about the possibility of an ice storm putting so much hard ice on the cable that the weight of the ice forces the cable down!?
    -ice storms sometimes bring trees and electric cables down this way!

    -the list of theoretical dangers just goes on and on -it's a nightmare.
  13. 31 Jan '09 21:12 / 1 edit
    Originally posted by Metal Brain
    I have always been skeptical about the space elevator and the nanotubes are made of carbon. Doesn't carbon conduct electricity?

    If so, wouldn't the ionosphere send one of the biggest lightning strikes ever to the earth and destroy the elevator before it could even be used?
    …Doesn't carbon conduct electricity? .…

    I decided to look this up just to check that I got my facts right:

    http://en.wikipedia.org/wiki/Carbon_nanotube

    The article explains that there are semiconducting varieties of nanotubes that are moderately good at conducting electricity but also “metallic nanotubes” which are extremely good at conducting electricity. And it says:

    “…
    In theory, metallic nanotubes can carry an electrical current density of 4E9 A/cm2, which is more than 1,000 times greater than metals such as copper
    …”

    Wow! -I didn’t know that!
  14. 01 Feb '09 08:58 / 1 edit
    Diamonds only burn at very high temperatures and I would expect nanotubes to have a similar high temperature burning point.
    The issue of avoiding tracked objects could be solved simply by having a small jet engine on the counter wight so that it could sway from side to side. It would only need to move it a meter or two. I would expect it to be swaying quite considerably already due to winds etc in the atmosphere so it might simply be a matter of adjusting the length slightly to change the frequency in order to avoid known objects.

    If the cable was a good enough conductor then we might even be able to utilize the electricity generated - maybe that could power the vehicle that climbs up and down the cable!
    Good conductors do not heat up as much when electricity passes through them so I don't see heating as a major risk. If nanotubes are similar to diamonds in strength properties (I don't know this) then it is likely they can withstand high heat without much weakening.

    Regarding storm damage etc the solution is to use the same trick used by telescopes. Place the elevator in a very high altitude location that does not experience much bad weather.

    Of course it might be better to construct the first space elevator on the moon as that would remove a large number of the problems including: much lower total length and strength required, no winds storms and other atmospheric effects, less space trash (does the moon have any?).
    It also would benefit us more as our current problem with the moon is that we must take with us any fuel required to lift of again.
  15. 01 Feb '09 09:32
    Originally posted by twhitehead
    Of course it might be better to construct the first space elevator on the moon as that would remove a large number of the problems including: much lower total length and strength required, no winds storms and other atmospheric effects, less space trash (does the moon have any?).
    It also would benefit us more as our current problem with the moon is that we must take with us any fuel required to lift of again.
    A moon elevetor is impossible.

    An earthly elevator need to go up to and beyond a geostationary orbit *if* the mass of wire is neglected.
    What is a lunarstationary orbit? The answer to that gives the reason why a lunar elevator is impossible.