“Lunar Regolith and Moon Dust”
Mark Hyatt, a project manager at NASA GRC gave a presentation on the lunar regolith composition and formation, the problems it causes, and the technology being developed to overcome these problems. Hyatt received his baccalaureate from Alfred University and his Master’s degree from the Missouri University of Science and Technology. He started his career in ceramics at Glenn Research Center in 1985 and later transitioned into project management.
Hyatt began the presentation with an overview of the moon’s geography and makeup. The moon consists of a solid core, surrounded by a partially molten outer core, surrounded by a mantle layer, and the outer layer is a solid crust. The crust is much heavier on the dark side of the moon where it is bombarded with meteorites. Hyatt also highlighted some of the potential financial benefits of harvesting resources on the moon, as the crust is rich in titanium and hydrogen deposits.
Lunar regolith refers to the material on the lunar surface. It is formed from micrometeorite impacts in the presence of vacuum. The size of the particles ranges from nanoscale particles to particles typically found in Earth soil. Agglutinates are some the more common regolith structures, which are a conglomeration of particles bonded together by glass. This glass is formed when micrometeorites melt the some of the lunar soil and then it refreezes. Lunar regolith is further characterized by weathering from solar wind and cosmic radiation.
The problems with lunar regolith are numerous. The most pressing concern is its health impact on humans. For example, nanoscale iron surrounded by a glass shell has the potential to diffuse through human membranes and enter the bloodstream. There, the glass shell would dissolve and deposit the iron, which could lead to iron toxicity. The lunar dust is also an eye and lung irritant. The Apollo 12 astronauts complained of a pungent odor given off by the regolith and were bothered by it the entire way back.
Lunar regolith can also lead to problems with equipment. For one, the lunar regolith is very abrasive. One astronaut fell down on the moon and some of the regolith got stuck to his visor. When he tried to wipe it off, it scratched the visor and he had difficulty seeing for the rest of the trip. Secondly, the lunar regolith can clog up mechanical equipment and it causes traction problems. The Apollo landers had difficulty detecting their approach velocity and altitude on landing because the lunar dust kicked up by the rockets interfered with the instruments’ readings. In addition, the regolith can also lead to cooling problems with lunar equipment. Because there is no atmosphere on the moon, the only way to dissipate heat is by radiating it too space. Lunar dust can accumulate on batteries and radiative surfaces, insulating them and therefore decreasing the efficacy of radiation cooling. Finally, solar wind and radiation causes charges to build up in the soil, which could short electrical instruments.
It is difficult to design equipment to overcome the above problems and operate in a lunar environment because of NASA’s technology ready level 6 (TRL 6), which states that a demonstration must be made in a relevant environment. It is obviously rather difficult to constantly send equipment to the moon for testing, and the astronauts only brought back 842 pounds of regolith from the moon. Thus, stimulants are required to represent the lunar regolith and demonstrate technology, such as how to best remove the dust.
The stimulants are evaluated on particle size distribution and shape, adhesion, abrasion, surface reactivity and chemistry, and composition. All stimulants have slightly different properties and all of them differ slightly from the actual regolith. It is difficult to simulate the regolith exactly because chemicals in Earth’s atmosphere and contaminants, such as shoe leather, have reacted with and contaminated the original regolith samples. In addition, some properties of the regolith, such as how sticky it is, are present only in the moon’s extreme vacuum. For example, in vacuum, the intermolecular forces between two objects (which pulls things together) can overcome the local pressure forces from the atmosphere (which keeps things pushed apart).
Hyatt explained that accurate stimulants are important in order to develop the technological readiness of future technologies for lunar operations. For example, how to best clean surfaces in order to maximize their effectiveness at radiating heat is on obvious concern. Some studies are focusing on lunar regolith’s reactivity and magnetic susceptibility in order to figure out better cleaning and removal techniques. It is important to accurate model particle size to determine the best methods for filtering air in lunar habitats.
Hyatt concluded the meeting with some amazing videos of the Apollo missions. One of the videos showed the astronauts flooring the lunar rover on the moon and the other video showed an astronaut trying to pick up a hammer that he dropped. The pressure suit was making it difficult for him to bend over, which lead to amusing “hammer dance.”