Many missions, manned and robotic, have been sent to the moon. It seems likely that future space exploration will need a base there. To transport a base and construct it by rocket all the way there is a costly and risky business. Space elevators have been suggested here and elsewhere, but there are great problems from an earthbound point of view - the Earth's atmosphere, weather, rotation, plate tectonics, tidal pull... However, the moon presents no atmospheric problems, the surface gravity is lower, and... it has one hemisphere which always faces more or less directly towards the Earth.
An elevator shaft from the moon towards the earth could be constructed in a similar modular way to construction derricks on the ground. Moreover such a shaft could reach almost to the earth's outer atmosphere, and would be stabilised by both the earth's and the moon's gravitational pull at either end, and there would be a gravitational null along the way. This means that by careful load balancing, much of the work in 2-way transportation of materials could be done by gravity, only using additional power to start and end journeys. A combined hydraulic lift and brake mechanism on the moon could be utilised to store kinetic energy. Then only shuttle trips into earth orbit would be required to get stuff to the moon elevator for transport there. The structure itself would have potential for colonisation and space research.
It should also be possible to start on a small scale with a single cable, and a continuous upgrade system to increase the load bearing ability of the structure. An analogy would be firing an arrow attached to a thread attached to a rope etc., in order to climb a cliff or cross a void. Small teams at first, building foundations and a base, then as the structure matures, much larger transports and additional elevators can be brought into play. Initially materials from Earth would be used, but later, materials of lunar origin would be wrought.-- TomBombardil, Mar 13 2004 Space elevator http://en.wikipedia...wiki/Space_elevator [ldischler, Sep 07 2006] Lunar space elevator http://en.wikipedia...unar_space_elevator [ldischler, Sep 07 2006] The Space Elevator Games http://www.spaceref...ewpr.html?pid=20558$400,000 prize - grab your fishing line and apply [wagster, Sep 08 2006] A Lunar Space Elevator Is Actually Feasible and Inexpensive, Scientists Find https://science.sla...ive-scientists-find [xaviergisz, Sep 18 2019] An interesting concept, except for one point. What about space junk and orbiting satellites? Would there not be a high probability of something crashing into the elevator? Also, what about the solar winds?-- Apologetic_Cynic, Mar 13 2004 Gets my (+).-- 2 fries shy of a happy meal, May 19 2005 Also, what about the fact that the moon isn't in geosynchronous orbit?-- Laimak, May 19 2005 On reading the title, I imagined a lift in a building where everyone faced the back and dropped their trousers. Quite relieved to discover the truth.-- AbsintheWithoutLeave, May 19 2005 Thank you for THAT, <awol>.
As for <laimak>'s question, I don't think the elevator is intended to reach all the way to the earth's surface. Tom specifies that the near end would be reached by "shuttle trips into earth orbit". Not saying it will be easy to build or anything, but it gets a bun from me.-- gardnertoo, Oct 08 2005 Couldn't the elevator end in a 'terminal' that hangs within the earth's atmosphere? This could be reached by a dirigible and would visit every point on the equator once a month.-- wagster, Sep 05 2006 No one except Laimak seemed to notice that the earth end will be moving at 1000 mph relative to the atmosphere, and at least 16,000 mph relative to any shuttle orbit.-- ldischler, Sep 05 2006 Hang on a sec, [ldischler], but doesn't the moon orbit the earth once a month? That means it moves over the surface of the earth at a sedate 35mph.-- wagster, Sep 05 2006 I assume you're joking, wags. Or did you forget that the earth rotates?-- ldischler, Sep 05 2006 Ahem. I forgot. <hides>-- wagster, Sep 05 2006 //1000 mph relative to the atmosphere, and at least 16,000 mph relative to any shuttle orbit//
I understand the 1000 mph, but not the 16,000 mph part; what is the constraint on possible shuttle orbits which gives rise to this this relative velocity? Or, to put in another way, what prevents a man-made object from taking up a luna-stationary orbit?-- pertinax, Sep 07 2006 Nothing at all. It's just that there's very little point in trying to access an elevator to the moon if you've already travelled out that far by shuttle.-- wagster, Sep 07 2006 //I understand the 1000 mph, but not the 16,000 mph //The shuttle is only capable of low earth orbit. (A major design flaw, but there you are.) Its typical orbital velocity is 17500 mph. The earth end of the elevator is flying at 1000 mph or so. So the best you could hope for is that they're going in the same direction, where the relative velocity is 16,500 mph.-- ldischler, Sep 07 2006 Here's another thing that I don't get, if anyone can explain it ([ldishler]?) - this space elevator idea has been discussed by some quite serious people since the 1960's, so it must be possible at least in theory. In order to work, one end must be in geostationary orbit...yes? About 42000km. The moon at around 35000-40000 will therefore pass between the space end and the earth end and smash the elevator to bits every day won't it?-- wagster, Sep 07 2006 You actually have to go further out than geosynchronous. But no worries, the moon is ten times further out than you said it was. (avg. distance is 382,500 km, not 40,000).-- ldischler, Sep 07 2006 Low earth satellites? Have we got a way of stopping them crashing into the elevator or are we going to cross that bridge when we come to it?-- wagster, Sep 07 2006 That's just one of the problems with this modern day tower of Babel.-- ldischler, Sep 07 2006 If we place the space end of the elevator in geostationary orbit but slightly off-axis longitudinally and hinge the earth end, it will avoid all those pesky equatorial satellites except for when it crosses the equator twice a day.
Then you just need huge laser cannons blasting offending craft to smithereens at those two times. Or something.-- wagster, Sep 07 2006 See the Wikipedia link, which says about a space elevator on Mars: "One simpler way to resolve the problem of Phobos (1.1 degree orbital inclination) or Deimos (1.8 degree orbital inclination) interaction is to position the tether anchor perhaps five (5) degrees off the Martian equator." It also discusses a lunar elevator.-- ldischler, Sep 07 2006 That's a great article. I like the idea of the laser broom to nudge unpowered satellites and debris out of the way.-- wagster, Sep 07 2006 //avg. distance is 382,500 km, not 40,000// By a strange coincidence I have just found out that the moon's perigee where it passes closest to earth was this evening at 20:30.-- wagster, Sep 07 2006 Thank you, [wagster] and [ldischler]. I get it now. :)-- pertinax, Sep 08 2006 If we had the engineering ability to construct such a device I think something simple like avoiding orbital debris would be well within our grasp. A simple system allowing for the structure to deflect realatively quickly by about 30 feet at any given point should be all that is required to avoid a collision.(we only need to miss by a millimeter) Basic radar monitoring would detect approaching objects and calculate any potential impact point and then move the structure if needed to avoid the hit. Something along the lines of a bimetal deflection or pinching of one side would cause a pucker in the cable and cause it to deflect.-- jhomrighaus, Sep 08 2006 NASA are doing an X-Prize style competition for the space elevator (link). As I understand it there are two competitions, one for tether (the long bit of string) and one for the climber.-- wagster, Sep 08 2006 [xaviergisz]; interesting. As some of the commenters at the link point out, they've completely ignored orbital eccentricity, which will render the idea impossible (unless there are huge "winders" at L1 to change the length of both sides).-- neutrinos_shadow, Sep 18 2019 I can see an Earth to Moon escalator might be handy, but not to forget the passport, or you have to go all the way down again.
Possibilities for consulates half way up to sell new passports for those lacking patience.-- not_morrison_rm, Sep 18 2019 //As some of the commenters at the link point out, they've completely ignored orbital eccentricity, which will render the idea impossible//
As one of the comments on Slashdot states:
//The distance variation is more like 42,000 km but geosynchronous altitude is only about 35,000 km so the cable would go from 14,000km above surface to 56,000 km above surface.//
So there would be better and worse times (when closer and further) to catch the end of the elevator.-- xaviergisz, Sep 19 2019 An earth-to-geosynchronous elevator could be used together with the geosynchronous-to-moon elevator.
The geosynchronous-to-moon elevator would pass the earth-to-geosynchronous elevator roughly once a day.
Once at the top of the earth-to-geosynchronous elevator you could transfer to the geosynchronous-to-moon elevator. You would need to accelerate to 3km/s to catch the moon elevator.-- xaviergisz, Sep 19 2019 Hmm, problems with the space escalator, first is it would take 101 days to get to moon, and second is the more tricky escalator etiquette, do you stand on the right or the left? Like in Japan..Tokyo is stand on the left, whereas Osaka is stand on the right.-- not_morrison_rm, Sep 19 2019 what happens if a micro meteorite hits the cable?
Seems like it's in the realm of the doable, but I've always thought propulsion will get solved before material science is sufficient.-- theircompetitor, Sep 19 2019 random, halfbakery