What is the best material for a moon tower?

As both the United States and China prepare for a sustained human presence on the moon, physical infrastructure on the moon will be critical to our long-term presence. Self-deploying towers are increasingly becoming one of the most important parts of physical infrastructure.

These towers can carry a host of equipment, from solar panels to communications arrays, and the more weight they can withstand under the moon’s gravity, the better. Therefore, it is essential to understand the optimal structural settings for these towers, which is the objective of a recent paper by researchers at North Carolina State University and NASA Langley Research Center.

Some of the technology behind its structure was developed under NASA’s Self-Erecting Lunar Observation Tower (SELTI) project. One of the most important technologies is the material from which the tower is constructed. The researchers investigated two types of materials in their study: a corrugated rotatable tubular boom (COROTUB) and a collapsible tubular mast (CTM).

First, let’s consider the design around COROTUB. COROTUB is a patented technology designed for use in small satellites. For example, it allows a CubeSat to fit into a relatively compact package while deploying antennas many times its size. Adapting this technology to a deployable boom mast for use on the lunar surface is the 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. When deployed, it can support a payload at the top of the mast. Although it appears to be much simpler in design than the COROTUB, it ostensibly has a similar weight limit.

However, one of the most important features of these towers is not the boom material itself, but the supporting structure (in this case, the cable). This paper considers designs with and without support cables that may cause the instrument to lean to one side against the force of the instrument at the top of the boom. Imagine a giant sunflower bending the pedal on one side, but on the other side a metal cable holds it in place.

Systems with this support cable construction perform well on nearly every criterion used by their creators. The method they used involves a type of mathematical analysis known as the Rayleigh-Ritz method, which is typically used to calculate structural loads. However, the calculations of these structures on the Moon are different from those on Earth. First, the gravity is much lower and there is no wind, which means you will need additional support.

However, the system should experience large temperature differences based on whether it is located on the bright or unlit side of the moon. As of now, these do not appear to be part of the calculations used in the analysis.

COROTUB and CMT are not the only technologies that may aim to solve this problem. We previously reported on Honeybee Robotics’ project LUNARSABER. Its 100-meter-tall mast solves problems similar to those addressed by COROTUB and CMT-based towers.

We don’t yet know what technology will be used in a completed prototype on the moon, but the fact that multiple organizations are researching this technology shows promise. And since hosting literal lights is one use case for these towers, it’s only a matter of time before more light shines on this technology and the lunar surface below.