Lunar space elevator
A proposed lunar transportation system using a tethered cable.
A lunar space elevator is a proposed transportation system for moving a mechanical climbing vehicle up and down a ribbon-shaped tethered cable set between the surface of the Moon and a docking port suspended tens of thousands of kilometers above in space. It is similar in concept to the Earth-based space elevator but, because the Moon's surface gravity is much lower, the engineering requirements can be met using materials and technology already available. The system could significantly reduce the costs and improve reliability of soft-landing equipment on the lunar surface, allowing the use of low-thrust drives such as ion drives that otherwise cannot land on the Moon.
- Type
- Proposed transportation system
- First conceived
- 1924 (Friedrich Zander, published posthumously in his collected works, 1977)
- Key concept published
- 1978 (Jerome Pearson, Acta Astronautica)
- Feasibility study
- 2005 (NASA Institute of Advanced Concepts, by Jerome Pearson)
- Primary material
- Commercially available high-strength para-aramid fibres (e.g., Kevlar, M5) or ultra-high-molecular-weight polyethylene fibre
- Stable positions
- Earth-Moon Lagrange point L1 or L2
Lore & Background
The idea of space elevators dates to 1960 when Yuri Artsutanov wrote a Sunday supplement to Pravda on building such a structure, though his article was not known in the West. In 1966, John Isaacs published a concept in Science using thin wires from a geostationary satellite, but it also was not widely known. In 1972, James Cline submitted a 'mooncable' concept to NASA, which responded negatively citing technical risk and lack of funds. Jerome Pearson independently developed the space elevator concept in 1975, publishing in Acta Astronautica, which brought the idea to the aerospace community and inspired Arthur C. Clarke's novel The Fountains of Paradise. In 1978, Pearson extended his theory to the Moon, using Lagrangian points instead of geostationary orbit. Posthumous publication of Friedrich Zander's collected works in 1977 revealed he had conceived of a lunar space tower in 1924.
Reader's Guide
The lunar space elevator represents a significant alternative to traditional rocket-based lunar transport. Because the Moon's low gravity allows construction with existing materials like Kevlar, the concept is technically feasible within current state of the art, as shown by a 2005 NASA Institute of Advanced Concepts study. The elevator could reduce launch costs for payloads bound for the lunar surface by a factor equal to the many times the landed mass required by conventional rockets. Its docking port could be positioned at the Earth-Moon Lagrange points L1 or L2, though these points are unstable and require small inertial adjustments. The system could be anchored near a lunar pole, with a tramway bringing the cable to the pole, and the Moon's low gravity allows much taller support towers than on Earth. A uniform cross-section tether is possible, enabling a double-tether pulley configuration that simplifies repairs. In October 2011, LiftPort announced it was pursuing a lunar space elevator as an interim goal before attempting a terrestrial elevator.
Did You Know?
- A lunar elevator could be constructed using commercially available high-strength para-aramid fibres such as Kevlar or M5, or ultra-high-molecular-weight polyethylene fibre.
- The Moon's slow rotation means the upper limb of the cable would have to be much longer than for an Earth-based system, or be topped by a much more massive counterweight.
- A uniform cross-section lunar space elevator could be built without any taper, unlike Earth-based designs which require a taper ratio of about 6000.
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