Lunar space elevator

A lunar amplitude elevator is a proposed cable active from the apparent of the Moon into space.

It is agnate in abstraction to the more good accepted Earth amplitude elevator abstraction (a cable abeyant aloft Earth, with its centermost of force hardly aloft geostationary orbit). It would instead be complete with its centermost of force in a anchored position aloft the apparent of the Moon, accouterment a controlled agency to carriage bodies and/or abstracts amid the apparent and lunar orbit.

A lunar elevator could decidedly abate the costs and advance believability of soft-landing accessories on the lunar surface. For example, it would admittance the use of mass-efficient (high specific impulse), low advance drives such as Ion drives which contrarily cannot acreage on the Moon. Since the cable would acquire a microgravity point, these and added drives can ability the cable from low Earth apogee (LEO) with actual basal launched ammunition from Earth. With accepted rockets, the ammunition bare to ability the lunar apparent from LEO is abounding times the landed mass, appropriately the elevator can carve barrage costs for payloads apprenticed for the lunar apparent by a agnate factor.

Location

There are two lunar-synchronous credibility area an elevator could be placed that would be stable: the libration credibility L1 and L2. L1 on the Earth ancillary of the Moon is 56,000 km up from the surface, and L2 on the far ancillary is 67,000 km up. In these positions, the armament of force and centrifugal force are equal, and as continued as the arrangement remained counterbalanced (L1 and L2 are in ambiguous calm forth the band amid Earth and Moon), it would abide stationary.

Both of these positions are essentially added up than the 36,000 km from Earth to geostationary orbit. Furthermore, the weight of the limb of the cable arrangement extending bottomward to the Moon would accept to be counterbalanced by the cable extending added up, and the Moon's apathetic circling agency the high limb would accept to be abundant best than for an Earth-based system. To append a kilogram of cable or burden aloof aloft the apparent of the Moon would crave 1,000 kg of counterweight, 26,000 km above L1. (A abate balance on a best cable, e.g., 100 kg at a ambit of 230,000 km — added than center to Earth — would accept the aforementioned acclimation effect.) Without the Earth's force to allure it, an L2 cable's everyman kilogram would crave 1,000 kg of balance at a ambit of 120,000 km from the Moon.

The ballast point of a amplitude elevator is commonly advised to be at the equator. However, there are several accessible cases to be fabricated for analysis a lunar abject at one of the Moon's poles; a abject on a aiguille of abiding ablaze could booty advantage of connected solar power, for example, or baby quantities of baptize and added volatiles may be trapped in assuredly black atrium bottoms. A amplitude elevator could be anchored abreast a lunar pole, admitting not anon at it. A tramway could be acclimated to accompany the cable the blow of the way to the pole, with the Moon's low force acceptance abundant taller abutment building and added spans amid them than would be accessible on Earth.

Fabrication

Because of the Moon's lower force and abridgement of atmosphere, a lunar elevator would accept beneath acrimonious requirements for the compactness backbone of the actual authoritative up its cable than an Earth-tethered cable. An Earth-based elevator would crave aerial strength-to-weight abstracts that are apparently possible, but not yet bogus in convenance (e.g., carbon nanotubes). Whereas, a lunar elevator could be complete application high-strength commercially accessible abstracts such as Kevlar or Spectra.

Compared to Earth, there would be beneath geographic and political restrictions on the area of the apparent connection. The affiliation point of a lunar elevator would not necessarily accept to be anon beneath its centermost of gravity, and could alike be abreast the poles, area affirmation suggests there ability be arctic baptize in abysmal craters that never see sunlight; if so, this ability be calm and adapted into rocket fuel.

Jerome Pearson has proposed a cable architecture application M5 cilia (See Materials, below) that would accept a accumulation of 6,100 tonnes including a massive counterweight, that would be able of appropriation or depositing endless of 2,000 newtons (450 lbf, or at lunar apparent gravity, masses of 1233 kg / 2700 lbm) at the base. The balance could potentially be aerial from the lunar surface.

Materials

Unlike earth-anchored amplitude elevators, the abstracts for lunar amplitude elevators won’t crave a lot of strength. Lunar elevators can be fabricated with abstracts accessible today. Carbon nanotubes aren’t appropriate to body the structure.[1] This would accomplish it accessible to body the elevator abundant sooner, back accessible carbon nanotube abstracts in acceptable quantities are still years away.[2]

One actual that has abundant abeyant is M5 fiber. This is a constructed cilia that is lighter than Kevlar or Spectra.[3] According to Pearson, Levin, Oldson, and Wykes in their commodity The Lunar Amplitude Elevator, an M5 award 30 mm advanced and 0.023 mm thick, would be able to abutment 2000 kg on the lunar apparent (2005). It would additionally be able to authority 100 burden vehicles, anniversary with a accumulation of 580 kg, analogously spaced forth the breadth of the elevator.[1] Other abstracts that could be acclimated are T1000G carbon fiber, Spectra 200, or Zylon. All of these abstracts accept breaking lengths of several hundred kilometers beneath 1g.[1]

Potential lunar elevator materials[1] Material↓ Density ρ

kg/m3↓ Stress Limit σ

GPa↓ Breaking height

(h = σ/ρg, km)↓

Single-wall carbon nanotubes (laboratory measurements) 2266 50 2200

Toray Carbon cilia (T1000G) 1810 6.4 361

Aramid, Ltd. polybenzoxazole cilia (Zylon PBO) 1560 5.8 379

Honeywell continued alternation polyethylene cilia (Spectra 2000) 970 3.0 316

Magellan bore polymer M5 (with planned values) 1700 5.7(9.5) 342(570)

DuPont Aramid cilia (Kevlar 49) 1440 3.6 255

Glass fibre (Ref Specific strength) 2600 3.4 133

The abstracts will be acclimated to body the ribbons which will affix from the L1 and L2 antithesis credibility to the apparent of the moon.[1] The ribbons would be acclimated by the automatic aggressive agent to get from the apparent into orbit.[1] The cartage would be slow, compared to actinic rockets, but it is a acceptable acceleration for appointment cargo.[1]

The ribbons are activity to be decumbent to accident by micrometeoroids from amplitude so one way to advance their survivability is to accomplish a multi-ribbon arrangement instead of one.[1] They will accept arrangement at approved intervals, so that if one area is damaged, the alongside sections would backpack the amount until automatic cartage can appear and alter the missing ribbon.[1] The arrangement would be spaced about 100 km apart, which is baby abundant to acquiesce a automatic climber to backpack the accumulation of the backup 100 km of ribbon.[1]

Climbing vehicles

One adjustment of accepting abstracts bare from the moon into apogee would be the use of automatic aggressive vehicles.[1] These cartage would abide of two ample auto acute adjoin the ribbons of the elevator to accommodate abundant abrasion for lift.[1] The climbers could be set for accumbent or vertical ribbons.

The auto would be apprenticed by electric motors, which would access their ability from solar activity or beamed energy. The ability appropriate to ascend the award would depend aloft the lunar force field, which drops off the aboriginal few percent of the ambit to L1.[1] The ability that a climber would crave to bisect the award drops in admeasurement to adjacency to the L1 point. If a 540 kg climber catholic at a acceleration of fifteen meters per second, by the time it was seven percent of the way to the L1 point, the appropriate ability would bead to beneath than a hundred watts, against 10 application at the surface.

One botheration with application a solar powered agent is the abridgement of sunlight during some genitalia of the trip. For bisected of every month, the solar arrays on the lower allotment of the award would be in the shade.[1] One way to fix this botheration would be to barrage the agent at the abject with a assertive acceleration again at the aiguille of the trajectory, attach it to the ribbon.[1]

Possible uses

Materials from Earth may be beatific into apogee and again bottomward to the Moon to be acclimated by lunar bases and installations.[1]

Former U.S. President George W. Bush, acclamation his Vision for Amplitude Exploration, noted[4] that the Moon may serve as a cost-effective construction, ablution and fueling armpit for approaching amplitude analysis missions.[5] As President Bush announced,[4] "Its clay contains raw abstracts that ability be harvested and candy into rocket ammunition or breathable air." For example, approaching Ares V missions could cost-effectively[6] bear raw abstracts from Earth for approaching aircraft and missions to a Moon-based[6] amplitude berth positioned as a counterweight[7] to a lunar amplitude elevator,[8] while ammunition and breathable air could be alien up from the Moon's apparent to the aforementioned Moon-based berth forth the aforementioned lunar amplitude elevator. As well, the absolute action bare for alteration amid the Moon and Mars is absolutely abundant beneath than amid the Moon and Earth, so lunar abject action could accomplish a ample appulse on architecture a Mars base. Since millions of tonnes of baptize ice accept been begin on the moon's poles, there is a abundant added attainable anatomy of baptize than the regolith.[9] The adjacency of the arctic abject on the lunar amplitude elevator to the baptize ice could accomplish mining the ice far added efficient.

The lunar elevator could additionally be acclimated to carriage food and abstracts from the apparent of the moon into the Earth’s apogee and carnality versa.[1] According to Jerome Pearson, there are affluence of assets on the moon that would be easier to accumulate and accelerate into Earth apogee rather than barrage from Earth.[1] He claims that one such actual which would be actual admired is lunar regolith, additionally accepted as moon dirt.[1] One accurate use for the regolith would be for massive actual to absorber amplitude stations or crewed abysmal amplitude missions adjoin solar flares, Van Allen trapped or catholic radiation. Other abstracts such as metals and minerals could be mined and beatific up for construction. Silicon for solar cells, as would be bare for the architecture of massive accessory solar ability stations, seems decidedly promising.

One disadvantage of the lunar elevator is that it may not be able to backpack animal passengers. The amount at which burden is transferred would be too slow, commonly demography weeks to ability its destination.[2] Humans would be able to get there faster by application rockets to and from the moon.