Talk:Lunar space elevator

message: There may be cost advantages in building the lunar space elevator from fibreglass rather than M5.  Fibreglass is made from silicon which is the second most common element in Lunar soil.  M5 is made from carbon which is very rare on the Moon and has to be brought from the Earth.  The skeleton of the cable can still be made from M5.  Andrew Swallow 05:49, 11 September 2007 (UTC)
thread_title:  Fibre Material 

message: The height of L1 and L2 given in this article and Pearson's report are different.  The ones in the report also have an error band.  The correct values need determining.
Andrew Swallow 19:24, 15 April 2007 (UTC)
thread_title:  Height of L1 and L2 

message: "A lunar space elevator ... is similar in concept to the better known Earth space elevator idea (a cable suspended above Earth, with its center of gravity in geostationary orbit)." -- "Center of mass" would be better in in this context than "center of gravity", yes? (center of gravity also redirects to center of mass) -- 201.51.239.119 17:59, 9 June 2007 (UTC)
replies: text: No, I don't think so. The center of gravity would be at geostationary orbit, but the center of mass would be much further out, close to the counterweight. But I welcome a third opinion. 81.235.136.245 00:25, 2 September 2007 (UTC)
replies: text: Center of gravity is a term used implying gravitional force acting on an object is equivalent to the total force acting through the center of mass.  In this case the lunar elevator is stabilized by a counterweight such that the design tension load is kept on the cable/tether stucture attached to the lunar surface.  The center of mass created by the counterweight and tether together would be only slightly above the lunar surface synchronous orbit.  Otherwise the tension in the tether/structure would be too great.   So there are three forces acting on the structure:  gravity through the center of mass of the system, centrifugal force out from unbalanced mass above the synchronous orbit, tension in the tether/structure to the surface.  Lazyquasar 02:56, 25 September 2007 (UTC)
replies: text: Careful here, gravity doesn't act at the centre of mass in any significantly non linear gravity field.WolfKeeper 03:30, 25 September 2007 (UTC)
thread_title:  "Center of gravity" vs "center of mass" 

message: There has recently been renewed interest in Satellite solar power as a partial solution of terrestrial energy problems, so far stymied by high launch costs from Earth.  The combination of the Pearson lunar cable with the Moon's abundant solar energy, silicon and oxygen (present in common oxides) offers the possibility of making solar cells on the Moon, raising them to L1 with the Pearson cable, assembling them there into SSPSs, and then moving them (with ion-electric drives) for use in Earth geosynchronous orbits. 
The question of the availability of carbon on the Moon, as the material of choice for such cables, deserves careful study.  Carbon minerals on Earth (coal, carbonate rocks like limestone, etc) are apparently mostly derived from organic precursors, yet carbonates and other carbon minerals are common enough in meteorites to suggest that they may not actually be very rare on the Moon.   Wwheaton (talk) 19:41, 16 April 2010 (UTC)
thread_title:  Key connection enabling Satellite Solar Power ? 

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thread_title:  External links modified 

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thread_title:  External links modified 

message: The article says, "A space elevator could be anchored near a lunar pole, though not directly at it," but this contradicts Pearson's "Lunar Space Elevators for Cislunar Space Development" (2005), which is the major source of information in the article. 
What Pearson says is
Using a ribbon of M5 fiber, the LSE bottom end could be towed to a latitude of about 36 degrees and retain about half its strength for lifting payloads. The maximum latitude attainable by M5 is 52.5 degrees, but that takes all its strength, leaving no margin for lifting payloads. Even carbon nanotubes could reach a latitude of only 76 degrees, which still leaves a distance of 426 km overland to the pole. This means that a tramway will be required to reach the poles, no matter what the material. 
However, taking half the stress limit to reach 36 degrees saves only about 1000 km of tramway, but it halves the throughput of the entire system. Much higher productivity can be obtained by just using a vertical configuration, and taking the tramway the entire 2700-km distance from the equator to the pole. 
So a more accurate statement would be that a space elevator does not have to be anchored precisely at the equator, but very much deviation adds stress to the cable and reduces the throughput of the system so much that any practical implementation will be anchored near the equator and use a tramway to reach higher latitudes.
Greg (talk) 18:35, 4 October 2021 (UTC)
thread_title:  Lunar Elevator Cannot Approach the Poles 

message: "At these points, the effect of the Moon's gravity and the effect of the centrifugal force resulting from the elevator system's synchronous, rigid body rotation cancel each other out. " 
That doesn't seem to fit what I think I understand about what happens at the Lagrange points or with this elevator.  Midgley (talk) 00:18, 7 January 2022 (UTC)
thread_title:  What keeps it up at L1