Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Space Elevator Update

  1. Feb 15, 2006 #1
  2. jcsd
  3. Feb 15, 2006 #2
    There actullay building a space elevator?I thought that was just somthing created that popluar secience had over extradded to get people to read there maginznes.

    I think it's cool that actullay doing this.That elevtor hasn't been around much longer then airplanes and there now building one to the moon.I wonder if about 100 years that going to be building an elevator that go to the moon.
     
  4. Feb 15, 2006 #3
    Yes i find this intereseting however, no, there will never be an elevator to the moon in 100 years.
     
  5. Feb 16, 2006 #4
    How the hell would they build an elevator attached to the moon? Does the moons orbit stay in sync (exactly) with the earths rotation?
     
  6. Feb 16, 2006 #5

    DaveC426913

    User Avatar
    Gold Member

    A space elevator does not go from Earth to Moon. It goes from Earth to GeoSync orbit - about 35,000km. There are variations, including ones that go out 60,000km further, but none get anywhere near the Moon.
     
  7. Feb 16, 2006 #6
    No I didn't mean an elevator that goes to the moon I ment one that can as far to the moon.Sorry for coffesing you
     
  8. Feb 16, 2006 #7
    im pretty sure it can only go to the point where the end of it would be in a geostationary orbit any farther and it would not remain perendicular to is point of tangency with the earth, probably begin to lean towards the earth and possibly fall, am i correct? the moon would be just to far.
     
  9. Feb 17, 2006 #8

    enigma

    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    It would need to go past GEO and then have some sort of counterweight put up there, blimkie.

    I have serious doubts that anyone who is trying to go forward with this has done any calculations regarding stability and vibrations of the wire.

    Doing a height/stress graph and seeing that, yes, the nanotube can hold itself below critical stress over the entire length is simply not going to cut it for a serious attempt. Any time someone tells me it can be done I just ask them how they're planning on damping the vibrations. I've not received an answer that even comes close to warranting an 'OK I'll buy that'.
     
  10. Feb 17, 2006 #9
    But if these people that say they are probably going to be able to build one by 2018, how the heck can they say that unless they have done all of the calculations? Surely they are not just bluffing, and saying that they can do it.
     
  11. Feb 17, 2006 #10

    Ivan Seeking

    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    The guy heading up one of these efforts was considered to be NASA's newest wonder boy.

    One approach is to use a series of climbers that would induce oscillations that would in turn be used to cancel natural ones that occur in the tether. The speed and direction of the the climbers could be varied in order to achieve this.
     
  12. Feb 17, 2006 #11

    russ_watters

    User Avatar

    Staff: Mentor

    No. The article is about a company doing pretty speculative research, to put it mildly. To be more blunt, I consider such companies to be near scams. The enabling technologies for a space elevator just aren't there and they are building things that look to non-techies to be stepping stones - and using the demostrations to make money. But a 1 mile carbon-fiber cable is not a step on the way to a space elevator and people need to be very careful about supporting such companies. And NewScientist does a disservice to its readers by titling the article "space elevator tether...." - the cable used in the test/demonstration/publicity stunt is not a space elevator tether.
    IMO, that's the stage it is really at.
    Why can't they just be bluffing? And even if they are serious - does being serious guarantee success?
     
    Last edited: Feb 17, 2006
  13. Feb 17, 2006 #12

    Ivan Seeking

    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    http://science.nasa.gov/headlines/y2000/ast07sep_1.htm
     
    Last edited: Feb 17, 2006
  14. Feb 18, 2006 #13

    enigma

    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    I've read the Smitherman report, and to be honest, I wasn't impressed. It really just looked like a bunch of enthusiast engineers and physicists sat around with some technical illustrators for a few days and did the same back-of-the-envelope calculations which I did when researching this topic a few years ago. They then said that it would be feasible sometime in the late 21st century, drew some pictures and wrote up a few pages of pie-in-the-sky ideas.

    And I do believe that the people claiming that they'll be doing it by 2018 are bluffing. For pete's sake... the "test" they were doing was on a 1 mile long wire. 1 mile != 30,000 miles. That's like strapping a rubber-band propellor to a plane, test flying it, and saying that it's the first test for a supersonic jet in 15 years.

    Why am I convinced of this? Building a space elevator will take millions of man-hours of work to complete. It will certainly be more difficult than the Apollo program. You are simply not going to be able to do it with 20 guys in a warehouse somewhere, even if they have 10 or 15 years. A project of that scope needs government support and industry-wide participation. The simple fact is that I have seen no industry buzz in any of the magazines I read, and considering the priorities the current administration has set out for NASA (design and build a replacement for the shuttle, return to the Moon, start planning for Mars, etc.), I don't think there will be government support.

    Now don't get me wrong... I'm not saying it can't be done. I'm just saying that it will be the single most challenging engineering feat ever attempted by man. It most certainly will not be done by a single startup company doing "tests" on 1 mile long sections. You cannot get to orbit by building taller and taller ladders.
     
  15. Feb 18, 2006 #14

    enigma

    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    Wow. For which natural mode? The thing is 30,000 miles long. An aspect ratio of a bajillion. Probably have thousands of active modes, if you can even use modal analysis on it.

    A mouse farting in Guadalajarah would induce vibrations in that thing.

    I'd even bet that standard vibration analysis tools would break down simply because of the distances involved. If you tapped the ground end, the tip wouldn't know you hit it for minutes or possibly even hours later. What's the speed of sound in carbon nanotube? From here if it were made of steel, it would take an impulse at one end just under 3 hours for the other end to feel it.
     
    Last edited: Feb 18, 2006
  16. Feb 18, 2006 #15

    russ_watters

    User Avatar

    Staff: Mentor

    I'm much more forgiving of serious-but-overenthusiastic engineers getting carried away by their imaginations. At least there is a hint of realism in a 100 year timeframe. 15 years? Laughable, yes.
     
  17. Feb 18, 2006 #16

    Ivan Seeking

    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    Just playing here...

    One idea that strikes me is that we would use two tethers. One with an imposed current running through it, and another that acts as a conductor and resistor network - for induced currents - that would dissipate energy from the relative motion of the first condutor. In other words, motion of one tether relative to the other would do electrical work. Design the tethers such that they have different modes of oscillation and are held in close proximity to each other.
     
    Last edited: Feb 18, 2006
  18. Feb 18, 2006 #17

    FredGarvin

    User Avatar
    Science Advisor

    I was thinking the same thing. I would hate to see what the 2nd order is, let alone the tenth, hundredth ot thousandth. I don't think standard modal analysis would work. If it was to work, I think it would be orders of magnitude more complicated than that which is practice today. The cumulation of error in even the slightest amount over something 30,000 miles long would alone make any single answer meaningless.

    Aptly put.
     
  19. Feb 18, 2006 #18

    DaveC426913

    User Avatar
    Gold Member

    I think you underestimate how seriously this is being taken. I think you'll find a lot more research and work has been put into it than you thought. (I wish I could back that up by pointing you at some places, but I can't right now...)
     
  20. Feb 18, 2006 #19

    Ivan Seeking

    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    Part of the problem is that anyone who has solved serious problems has a large incentive to keep secret how they do it - or I should say, how they plan to do it.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?



Similar Discussions: Space Elevator Update
  1. Space elevator on Mars (Replies: 14)

Loading...