As SSP posted previously, a space elevator serving Earth holds great promise for reducing the cost of access to space but remains out of reach at least for a couple of decades as there are no existing materials strong enough to support their own weight in Earth’s gravity well. But a lunar space elevator (LSE) is possible with commercial polymers available today and could be built for about $2 billion according to Charles Radley, a Systems Engineer and AIAA Associate Fellow. In a paper available on Academia.edu he shows how a “… lunar elevator is both feasible and affordable, and indeed profitable.”
A functional LSE would require a tether of low mass material that is also strong enough to support its own weight in the Moon’s gravitational field. In addition, it needs to be robust enough to transport payloads reliably and repeatedly over the entire working distance in cislunar space. The LSE would be a very long tether extending from the Moon’s surface up to a station at the system’s center of mass (COM) located at either of two Earth-Moon Lagrange points, L1 or L2. The physics of the system requires that the tether extend beyond the COM terminating at a counterweight several thousand kilometers higher. For the L1 system, the tether extends about 58,000 km up from the Moon to the station at the COM and then extends another 220,000 km up (toward the Earth) to the counterweight.
Several high tensile strength, low mass polymers developed in the 1990s that fulfill the system requirements are commercially available in large quantities today (e.g. T1000TM, DyneemaTM and ZylonTM * ). A 48 ton system composed of the tether, the L1 COM station, a lunar surface attachment fixture (SAF), counterweight and payload climbers could be launched on a single Falcon Heavy vehicle.
Starting at L1, the deployment would begin with the counterweight and SAF simultaneously played out in opposite directions (up and down in relation to the Moon, respectively) unspooling the tethers at rates that maintains the COM station at the L1 position. Upon the SAF reaching the desired location on the Moon, it would be affixed to the surface by drilling down to a sufficient depth to anchor the structure such that it could adequately withstand tension and lateral forces.
When compared to chemical rocket operations on the moon, there is a significant cost reduction in lifting materials off the surface if multiple climbers are used and the frequency of their trips up and down the LSE is maximized. The cost reduction is on the order of 9X, enabling the system to pay for itself in one month. Radley concludes that:
“These large cost reductions are game changing and will enable major expansion of human activities beyond Earth orbit, and establish profitable lunar based industries.”
The Liftport Group, a collaborator on the paper, is administering The Alexandria Project, a database repository collecting and organizing questions about the infrastructure needed for development of an LSE toward creation of a requirements document.
* T1000G is a trademark of Toray Composite Materials America, Inc.; Dyneema is a trademark of Royal DSM NV; Zylon is a trademark of Toyobo Corporation
I wanted to ask Charles about maintenance and repair of this structure. It’s so gigantic. That factor favors more conventional rotating skyhooks.
The appeal of this design is the simplicity of putting cargo on a climber that just runs along the cable. But climbers mean wear and tear on the cable. This is one of the technical issues he identifies in his paper. How can this be done?
Good questions Kim. You may be able to contact him through Academia: https://independent.academia.edu/charlesradley