Physical infrastructure on the Moon will be critical to any long-term human presence there as both America and China are gearing up for a sustained human lunar presence. 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. The more weight they can support in lunar gravity, the more capable they become. It’s important 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 are critical for 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 used to construct the tower. The researchers studied two types of material: the corrugated rollable tubular boom (COROTUB) and collapsible tubular mast (CTM).
COROTUB is a patented technology that was designed for use with small satellites. It would allow a CubeSat to deploy an antenna many times its size while still being rolled into a relatively compact package. Adapting the same technology to deploy a boom mast for use on the Moon is an obvious next step.
CTM is commercially available from Opterus. It is designed to roll flat into a shape similar to the shape of a roll of tape. Once deployed, it is capable of supporting a payload attached to the top of the mast. Its design is much simpler than COROTUB’s, but they have almost equivalent weight limits.
However, one of the most important features of these towers doesn’t lie in the boom material itself but in the supporting structure which is a cable. The research paper considers 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. Picture 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 better by pretty much every metric the authors used. The methods they utilized included a type of mathematical analysis known as the Rayleigh-Ritz method. This technique is typically used to calculate loads on structures. However, the math for those structures on the Moon is different from the same types of structures on Earth. For one, much less gravity and no wind would require additional support which may be counterintuitive. However, the system must survive massive temperature differences based on whether it is day or night 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 designs that could solve this problem. Project LUNARSABER was developed Honeybee Robotics. It is a one hundred- and - ten-yard-tall mast that would solve a problem similar to the one addressed by COROTUB and CMT-based towers. While it remains to be seen which technology is ultimately used on the Moon, the fact that more than one organization is looking into this technology is a good indication of promise.