Lunar dust remains one of the biggest challenges for a long-term human presence on the Moon. Its jagged, clingy nature makes it naturally stick to everything from solar panels to the inside of human lungs. And while we have some methods of dealing with it, there is still plenty of experimentation to do here on Earth before we use any such system in the lunar environment. A new paper in Acta Astronautica from Francesco Pacelli and Alvaro Romero-Calvo of Georgia Tech and their co-authors describes two types of flexible Electrodynamic Dust Shields (EDSs) that could one day be used in such an environment.
EDSs have been the front-runner for actively dealing with lunar dust for some time. They work based on the electric curtain effect, where charged and neutral particles are forced away from a surface by an electric field surrounding it. Think of the “shields” on the ships of Star Trek or Star Wars, but designed to deflect dust rather than laser or photon cannon fire. They’ve been proven effective at protecting flat infrastructure, such as solar panels, but not all infrastructure on the Moon is going to be flat, and many types of EDSs don’t deal well with curved surfaces.
One style the authors decided to test was copper-based. Copper, the most standard electrical conductor used in everything from circuit boards to motors, is cost-effective and rapidly manufacturable. It can be bent into all kinds of shapes, and adapt to curved surfaces. However, its weakness, like many metals, is repeated bending. The electrodes of these systems can crack after repeated bending, making them useful for static placement, but less so for shielding that must be moved from one location to another.
Video showcasing the tech from the team at Georgia Tech. Credit - Low-Gravity Science and Technology Laboratory YouTube ChannelAn alternative that solves that problem is Chemically Modified reduced Graphene Oxide (CMrGO). This was a novel type of electrode developed from nanocomposites by the Georgia Tech team that is specifically designed to withstand both static and cyclical straining. Part of that strain would also come from the extreme temperature swings of the lunar far side and near side, which will physically change the sizes of many types of electric conductors.
Temperature swings weren’t really part of the experimental model the team ran, though. They used lunar simulants purchased from The Exolith Lab in a pressure chamber ranging down to around 10 billion times lower than the atmospheric pressure of Earth, but still 10,000 times that of the Moon itself. They also blessed the simulant with ultraviolet light to simulate the photoionization the dust undergoes on the Moon’s surface.
Unfortunately, there are some limitations to how well simulants really mimic lunar dust. The processing systems they are created by typically don’t end up with the same jagged edges, and the UV activation like the Georgia Tech team used is the best approximation we can come up with of actual lunar dust charges here on Earth. On the lunar surface, the dust is much harder to deal with in both ways, though NASA did recently send a EDS mission on Firefly’s Blue Ghost mission to protect radiators and glass directly on the surface.
Fraser discusses how EDSs are used today.Back on Earth, the authors ran several experiments with their curved EDSs, with the main difference being whether dust was already settled or whether there was “dynamic dusting” actively ongoing. Basically, how well do the systems work repelling dust that is already attached compared to keeping it from attaching in the first place.
Copper (or more specifically copper-polyimide) samples performed really well, with over 90% of dust removed even when settled - as long as appropriately high voltages (over 3 kilovolts) are used. CMrGO-based EDs were slightly less effective, with 60% efficiency in dust removal when settled. They seemed to be limited by micro-discharges caused by an absence of dielectric coatings around the conductors that would allow them to arc between each other. However, both copper and CMrGO managed to keep almost all of the dust away completely when in a dynamic dust environment, showing that they are effective at stopping long-term build up.
For now, none of these systems have been adopted for any near-term lunar mission. However, with plenty of those planned by both America and China in the coming years, it might be only a matter of time before we see flexible, curved patches running over the top of habitats, rovers, and other surfaces to protect them from the Moon’s more pervasive, and annoying, material.
Learn More:
F. I. Pacelli et al. - Flexible electrodynamic dust shields for lunar missions
UT - When Moon Dust Becomes a Weapon!
UT - The Sticky Problem of Lunar Dust Gets a Mathematical Solution
UT - Modeling the Fight Between Charged Lunar Dust and Spacecraft Coatings
