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We have all heard about the idea of space elevators, a cable so long that it literally reaches into outer space, to be used for launching payloads cheaply into Earth and interplanetary orbits. However, the technologies for building such a device on Earth simply aren't there yet, due to our planet's deep gravitational well.

The Moon however has less mass, and a correspondingly shallower gravitational well, with surface acceleration of $1.6 m/s^2$, about 16% of Earth's.

Can we build a space elevator on the Moon with present technology? Is there any back of the Google-spreadsheet way of estimating if it were technologically feasible from an engineering standpoint? I'm not going to go into cost, since that might have to involve the idea of building an industrial capacity on the Moon, etc.

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I read a paper (I believe by Ben Bova in relation to his book, Mercury). In the paper it was claimed that we could actually build such a structure on Mars with current technology. That was written about 15-20 years ago.

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  • $\begingroup$ The "Red Mars" trilogy is by ‎Kim Stanley Robinson, no? $\endgroup$ – Serban Tanasa Sep 29 '15 at 16:39
  • $\begingroup$ Yes, sorry. I think it was still Ben Bova, but in relation to his book, "Mercury", instead. My confusion was that both authors use space elevators and both have one that falls. $\endgroup$ – Michael Richardson Sep 29 '15 at 16:42
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Yes! We absolutely can make a space elevator on the Moon with current technology. The lower gravity means we can use materials we already know how to mass-produce, such as "Kevlar, Spectra or M5 Fibre", and we don't need to rely on carbon nanotubes or graphene (which we can only produce in small quantities).

A lunar elevator would be longer than an Earth elevator, because it would have to reach one of the Earth-Moon Lagrange points rather than synchronous orbit — 56,000 km from the surface of the Moon for the closest Lagrange point, rather than 36,000 km from the surface of the Earth for geosynchronous orbit.

Source: https://en.wikipedia.org/wiki/Lunar_space_elevator

(I originally misread the title as "to the Moon", which would have been a resounding "no"…)

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Depending upon the time frame allowed for building using current technology, the answer may actually be, no we cannot build a practical space elevator for the moon with present technology.

Our current global lift capacity is fairly pathetic, about 80 launches per year with an average payload of about 2000 kg. Our capacity is even worse if you consider not just LEO but travel to one of the Lunar Lagrange points.

A lunar space elevator with a lift capacity of 100 kg (162 Newtons) is pretty close to the weakest useful elevator imaginable, only useful for bootstrapping additional cable lift. 10,000 kg is much more realistic for a minimum function elevator. Ignoring the weight of the elevator cable itself, you need a counterbalance of 10,000,000 kg at a distance of 120,000 km to support a 10,000 kg lift at the surface. We could not build this elevator for a long time to come.

Adding in all of the logistics, support, etc. to actually get this accomplished with maintenance, etc., this seems like a task that requires a new launch technology if nothing else.

There are launch designs on the board that could provide the needed lift capacity, but I would not classify them as existing, but possibly near future.

Economic justification is of course another problem.

For the pro elevator viewpoint, the best reference is probably NASA's paper, LUNAR SPACE ELEVATORS FOR CISLUNAR SPACE DEVELOPMENT

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Though gravity would absolutely challenge our technology in building a space elevator on Earth, the drag imposed upon the elevator by our atmosphere is also a very significant inhibiting factor.

Would it be worth it to spend resources to build and maintain a space elevator on the moon? Unlikely. Achieving lunar orbit from a lunar surface launch is trivial in comparison to achieving Earth orbit.

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    $\begingroup$ Hello Matt. Your answer doesn't really address the question of whether a space elevator on the moon is possible and what answer you offer doesn't have any justification. Would you mind adding in some justifications for your assertions? $\endgroup$ – Green Sep 29 '15 at 18:34
  • $\begingroup$ Downvoted for lack of justification of main points. $\endgroup$ – NPSF3000 Nov 24 '15 at 2:46
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    $\begingroup$ Achieving lunar orbit from a lunar surface launch is trivial in comparison to achieving Earth orbit Maybe so but achieving Earth orbit to Lunar orbit is harder than Earth orbit to [end of Earth-facing lunar space elevator] and would be worth the cost... $\endgroup$ – Scott Downey Nov 25 '15 at 14:17
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    $\begingroup$ Some specific numbers: Earth surface to Low Earth Orbit is about 7.5 - 8.0 km/s, depending on specifics. LEO to Low Lunar Orbit is about 4.0 km/s. LLO to lunar surface is about 1.9 km/s. (Source for the latter two.) Double these delta-v budget figures if you want a return ticket. Getting from the surface of the Earth to low Earth orbit is significantly harder in terms of delta-v than getting from low Earth orbit to the lunar surface. $\endgroup$ – a CVn Nov 25 '15 at 14:37

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