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9.22.2005

Lunar Lift

Interesting idea to build a space elevator on the moon. It would then be cheaper to send material into Earth's orbit from the moon than from the earth.

Further, you wouldn't need carbon nano-tubes because the moon is so much less massive.

Further, an easily available supply of Helium-3 on the moon could power all of the US.

5 Comments:

At 12:17 PM, Blogger joško said...

I've read about this before. It's very exciting!

The thing about amoon elevator that's not mentioned is this: the 'outward force' holding up the elevator doesn't come from a spinning moon (the moon only spins once a month, and thus you'd need a super long cable to balance out centrifugal* and gravitational centripetal forces).
The real tension comes from extending an elevator from the moon to the so-called 'Lagrange Point.' These are points in a system of co-orbiting bodies where gravity is cancelled out. There are five of them, and the one between earth and the moon would be the appropriate one to use. What'd really be holding up a Lunar Elevator, then, would be a balance between earth and moon gravities.

For a word on Helium3, it's only useful as a fuel source if you've mastered fusion! And if you've mastered fusion, why not extract H3 from the oceans on earth? It may not be super abundant there, but I reckon it'd be easier than going to the moon for it...

*As a physicist, I feel a need to explain a little bit the differences between centrifugal and centripetal forces. The two forces are equal in magnitude and opposite in direction. The centrifugal force does not act on the body in motion (people confuse this into saying it doesn't exist); the only force acting on the body in motion is the centripetal force. The centrifugal force acts on THE SOURCE of the centripetal force to displace it radially from the center of the path. Thus, if you're twirling a mass on a string, the centripetal force transmitted by the string pulls in on the mass to keep it in its circular path, while the centrifugal force transmitted by the string pulls outward on its point of attachment at the center of the path. The centrifugal force is often mistakenly thought to cause a body to fly out of its circular path when it is released--bolongna; rather, it is the removal of the _centripetal_ force that allows the body to travel in a straight line as required by Newton's 1st law.

 
At 12:34 PM, Blogger Miguel said...

So is it anchored to a specific place on the moon? Wouldn't it need to move on the surface of the moon (even if just to spin in a circle at a pole)?

 
At 1:13 PM, Blogger joško said...

The moon always shows earth the same face, so the base of the elevator wouldn't have to move at all. I even read that it's okay to have the base at high lunar latitudes, i.e., not on the lunar equator (it'd just mean an angled elevator).

 
At 1:19 PM, Blogger Miguel said...

I guess that makes the whole three poles thing more plausible than I'd thought...

 
At 1:27 PM, Blogger joško said...

This begs a new Space Commander Card: Lunar Space Elevator! ---Link any pole to any of your (or ANY?) space stations. Hmm... we'll figure it out.

 

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