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

Lunar space elevator

  1. Apr 6, 2010 #1
    Building a space elevator for the moon seems doable with existing materials (see the wikipedia page). So my question is why is no country or organization interested in building one?
     
  2. jcsd
  3. Apr 7, 2010 #2

    sophiecentaur

    User Avatar
    Science Advisor
    Gold Member
    2017 Award

    I guess it's partly because no one is actually planning to spend a lot of money actually getting there at all, at the mo. It may be quite 'do-able' and it sounds like a very satisfying idea from the engineering point of view BUT it would cost quite a bit more than just sending a manned expedition with a conventional launch system for returning.

    In the very distant future, such a construction would be a great test bed for doing the same on Earth. Once we've sorted out the food, the climate and the health issues, it sounds like a fab project for us to get started on. Whilst there are still people, down here, hacking each other to pieces and starving, it sounds a bit of a luxury, to me.
     
  4. Apr 7, 2010 #3

    Mech_Engineer

    User Avatar
    Science Advisor
    Gold Member

    You have to get stuff to the moon before you can launch/capture with a space elevator on it. Right now Earth's gravity well is the limiting factor.

    It's true, landing and taking off from the moon is easy compared to escaping Earth's gravitational pull. It's unlikely a space elevator on the moon would be cost effective unless there was a large amount of "stuff" being shipped to and from it.

    The only parallel is that it's a geo-(leo?)-synchronous elevator on a rotating celestial body. Earth's space elevator problem is made infinitely more difficult with a thick atmosphere, large numbers of currently orbiting satellites, and much larger gravity well.

    Well we won't get anything done then, because I seriously doubt those problems will ever completely diasappear!
     
  5. Apr 7, 2010 #4

    sophiecentaur

    User Avatar
    Science Advisor
    Gold Member
    2017 Award

    "Well we won't get anything done then, because I seriously doubt those problems will ever completely disappear! "
    Yes, I take your point but there are some projects that have a bit more 'worthy' which could be both fun and a bit more justifiable.
    I, personally, have a problem with the 'Buck Rogers' / 'wild west' / 'new frontier' approach to Space exploration. I just can't see the extreme glamour involved with actually getting people out there, bearing in mind the immense expense and value (scientific) for money. Unmanned missions seem to offer at least as much useful information at a fraction of the cost.
     
  6. Apr 8, 2010 #5
    Forget it! The rotation period of the moon is 28 days. To incorporate the orbiting platform that would be needed for the elevator at that rate would require an incredibly high orbit (I won't bother trying to figure how high.) In any case, there are other ways of throwing an object off the moon that are so much simpler and cheaper, like for example, a maglev launcher, once the cost of getting it to the moon is solved.

    KM
     
  7. Apr 8, 2010 #6
    On second thought, it might be dimly possible to run an elevator from the moon to one of the Earth-Moon lagrange points (That is, from Earth to Moon, not from Earth-Moon to Sun). There are five such points, but the only reasonably stable ones are the one that leads the moon around the Earth and the one that trails the Moon. It's still a pretty impractical idea. It would be far cheaper to just fire off the moon. Remember, it didn't take much to get the lunar lander off. I wonder how many world GNP the elevator would cost.

    KM

    Reference http://www.physics.montana.edu/faculty/cornish/lagrange.html" [Broken]:
     
    Last edited by a moderator: May 4, 2017
  8. Apr 8, 2010 #7

    russ_watters

    User Avatar

    Staff: Mentor

    It isn't the rotation of the moon that would be problematic (since the moon always presents the same face to earth), it is the rotation of earth that would be the problem. A lunar space elevator would need to be anchored to a tramway that wraps around earth's equator and moves at 1,000 mph. Building the tramway would on its own be by far the largest engineering project ever attempted.
     
  9. Apr 8, 2010 #8

    D H

    User Avatar
    Staff Emeritus
    Science Advisor

    A lunar space elevator would not reach from the Moon to the Earth, Russ. It would reach from the surface of the Moon to a bit below the Earth-Moon L1 point, or from the surface of the Moon to a bit above the Earth-Moon L2 point.
     
  10. Apr 8, 2010 #9

    russ_watters

    User Avatar

    Staff: Mentor

    Boy, I must have been halucinating when I looked at the wiki. I could swear the diagram was showing the earth and the moon! Sorry...
     
  11. Apr 9, 2010 #10

    sophiecentaur

    User Avatar
    Science Advisor
    Gold Member
    2017 Award

    I'm so embarrassed at not spotting that one myself! Now, if they could just speed up the Moon's rotation a bit. . . .
     
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook