Editing Lunar space elevator (section)

==Materials==
Unlike earth-anchored space elevators, the materials for lunar space elevators will not require a lot of strength. Lunar elevators can be made with materials available today. Carbon nanotubes aren’t required to build the structure.<ref name="Pearson 2005">{{cite web| url=http://www.niac.usra.edu/files/studies/final_report/1032Pearson.pdf| last=Pearson| first=Jerome| date= 2005| title=Lunar Space Elevators for Cislunar Space Development Phase I Final Technical Report| author2= Eugene Levin |author3=John Oldson |author4=Harry Wykes |name-list-style=amp }}</ref> This would make it possible to build the elevator much sooner, since available carbon nanotube materials in sufficient quantities are still years away.<ref name="Cain 2004">Cain 2004</ref>

One material that has great potential is [[M5 fiber]]. This is a synthetic fiber that is lighter than Kevlar or Spectra.<ref>Bacon 2005</ref> According to Pearson, Levin, Oldson, and Wykes in their article The Lunar Space Elevator, an M5 ribbon 30&nbsp;mm wide and 0.023&nbsp;mm thick, would be able to support 2000&nbsp;kg on the lunar surface (2005). It would also be able to hold 100 cargo vehicles, each with a mass of 580&nbsp;kg, evenly spaced along the length of the elevator.<ref name="Pearson 2005"/> Other materials that could be used are T1000G carbon fiber, Spectra 200, [[Dyneema]] (used on the [[YES2]] spacecraft), or [[Zylon]]. All of these materials have [[specific strength|breaking lengths]] of several hundred kilometers under 1''g''.<ref name="Pearson 2005"/>

{| class="wikitable sortable"
|+ Potential lunar elevator materials<ref name="Pearson 2005"/>
|-
! Material
! Density ''ρ''<br>kg/m<sup>3</sup>
! Stress Limit ''σ''<br>GPa
! Breaking height<br>(''h'' = ''σ''/''ρg'', km)
|-
| Single-wall carbon nanotubes (laboratory measurements)
| 2266
| 50
| 2200
|-
| Toray Carbon fiber (T1000G)
| 1810
| 6.4
| 361
|-
| Aramid, Ltd. polybenzoxazole fiber (Zylon PBO)
| 1560
| 5.8
| 379
|-
| Honeywell extended chain polyethylene fiber (Spectra 2000)
| 970
| 3.0
| 316
|-
| Magellan honeycomb polymer M5 (with planned values)
| 1700
| 5.7(9.5)
|342(570)
|-
| DuPont Aramid fiber (Kevlar 49)
| 1440
| 3.6
| 255
|-
| Glass fibre (Ref [[Specific strength]])
| 2600
| 3.4
| 133
|}

The materials will be used to manufacture the ribbon-shaped, tethered cable which will connect from the {{L1}} or {{L2}} balance points to the surface of the moon. The climbing vehicles which will travel the length of these cables in a finished elevator system will not move very fast, thus simplifying some of the challenges of transferring cargo and maintaining structural integrity of the system.
However, any small objects suspended in space for extended periods of time, like the tethered cables would be, are vulnerable to damage by [[micrometeoroid]]s, so one possible method of improving their survivability would be to design a "multi-ribbon" system instead of just a single-tethered cable.<ref name="Pearson 2005"/> Such a system would have interconnections at regular intervals, so that if one section of ribbon is damaged, parallel sections could carry the load until robotic vehicles could arrive to replace the severed ribbon. The interconnections would be spaced about 100&nbsp;km apart, which is small enough to allow a robotic climber to carry the mass of the replacement 100&nbsp;km of ribbon.<ref name="Pearson 2005"/>