What’s the Best Material for a Lunar Tower?

Physical infrastructure on the Moon will be critical to any long-term human presence there as both America and China gear up for a sustained human lunar presence. Increasingly, a self-deploying tower is one of the most essential parts of that physical infrastructure. These towers can hold numerous pieces of equipment, from solar panels to communications arrays, and the more weight they can hold in the lunar gravity, the more capable they become. So it’s essential to understand the best structural set-up for these towers, which is the purpose of a recent paper by researchers at North Carolina State University and NASA’s Langley Research Center. 

Several technologies underpin that structure, which was developed under NASA’s Self-Erectable Lunar Tower for Instruments (SELTI) project. One of the most important technologies is the material the tower consists of. In their study, the researchers looked at two types of material: the corrugated rollable tubular boom (COROTUB) and collapsible tubular mast (CTM). 

Let’s consider the design around COROTUB first. COROTUB is a patented technology designed for use with small satellites. For example, it would allow a CubeSat to deploy an antenna many times its size while still being rolled into a relatively compact package. Adapting the technology to a deployable boom mast for use on the Moon is an obvious next step. 

CTM, on the other hand, is commercially available from Opterus. It is designed to roll flat into a shape similar to a roll of tape. Once deployed, it is capable of supporting a payload located at the top of the mast. Its design seems much simpler than COROTUB’s, but on the surface, they have almost equivalent weight limits.

However, one of the most essential features of these towers doesn’t lie in the boom material itself but in the supporting structure – in this case, that is a cable. The paper looks at designs with and without supporting cables that could counteract the force of the instruments at the top of the boom, forcing them to slouch to one side. Imagine a giant sunflower with its pedals bending to one side, but on the other side, there’s a metal cable holding it in place.

The systems with this supporting cable structure perform superiorly by pretty much every metric the authors used. The methods they used included a type of mathematical analysis known as the Rayleigh-Ritz method, which is typically used to calculate loads on structures. But the math for those structures on the Moon is different from the same on Earth. For one, much less gravity and no wind would require additional support. 

However, the system must undergo massive temperature differences based on whether it is located on the lit or unlit side of the Moon. For now, those did not seem to be part of the calculations used in the analysis.

COROTUB and CMT are also not the only potential technologies looking to solve this problem. We previously reported on project LUNARSABER from Honeybee Robotics, whose 100m tall masts would solve a problem similar to the one addressed by COROTUB and CMT-based towers. While it remains to be seen which technology is used on a complete prototype on the Moon, the fact that more than one organization is looking into the technology is a good indication of promise. And since hosting literal lights is one of the use cases for these towers, it is only a matter of time before more light is shone on this technology – and the lunar surface underneath it.

Learn More:
J Daye, A Lee, & J Fernandez – Structural Architectures for Self-Erecting Lunar Towers
UT – A Tower On The Moon Could Provide Astronauts With Light, Power, and Guidance
UT – NASA’s New Solar Sail Extends Its Booms and Sets Sail
UT – A Moon Base Will Need a Transport System

Lead Image:
Artist’s conception of a Moon Base.
Credit – ESA – P. Carril