Ball Milling Techniques For Use With Lunar Regolith

HUMAN EXPLORATION AND OPERATIONS

Joren Bowling

Lunar Regolith, being easily accessible at most any location on the Moon’s surface, will inevitably play a crucial role in future construction and industry on the Moon (Sanders et al, 2021). Unprocessed Lunar Regolith, however, contains on average 30% to 50% by weight of grain sizes over 100um, which are disfavorable for use in industrial processes such as additive manufacturing or chemical processing. For example, in the sintering of regolith simulant Meurisse (2017, pg.7) noted a 70% increase (69MPa to 143MPa) in the compressive strength of sintered regolith following the addition of finer-grained (below 50um) stock instead of larger-grained (125um-300um.) stock. Similarly, Froth Flotation, a method of separating particles of ore from waste, can only be applied to particles that are less than 150um (Rao 2016, Pg.195). The purpose of this proposal is to determine the efficacy of various methods of ball milling in order to decrease the average grain size of lunar soil to a more preferable size for industrial use in a vacuum environment. Ball milling, similar to other types of tumbling mills, is the use of a rotating cylinder filled with a milling media - usually steel balls - to grind rock into fine particles as displayed in Figure 1 (Gupta, 2003, p.143). It, along with other similar methods of tumble milling, are the most common methods of rock grinding utilized in the mining industry, especially here in Alaska. While ball mills in use in the Alaskan mining industry here on Earth are not operated in a vacuum, opening doors to the expansion to off-world mining has the potential to dramatically affect Alaska - which is already in a special position regarding mining in extreme environments. Ensuring a regular supply of processed regolith will enable further growth and efficiency of resource processing in Lunar industry, aligning particularly with NASA’s Technology Taxonomy focus TX07.1.2, Resource Acquisition, Isolation, and Preparation.

The anticipated investigation will include the construction of a ball mill to be tested in various configurations such as differing milling media size and material and varying fill ratios, all ideally performed in conditions as close to the Lunar surface as possible. Mill conditions include those most similar to standards utilized in the mining industry, in addition to conditions not often used in industrial-scale mining. The anticipated results will include an analysis of mill operation and fill conditions compared to the change in grain size due to milling, power draw, and milling media loss and wear, along with variables such as temperature over the duration of the experiment. The intended conclusion will center around a mode of operation that maximizes grain size reduction and minimizes wear and power consumption.

Profile

Name: Joren Bowling, Undergraduate Student

Institution: University of Alaska Fairbanks

Major: Mining Engineering and Mechanical Engineering

Mentor: Dr. Orion Lawlor, oslawlor@alaska.edu

Award: Apprenticeship

Funding Period: 2021 to 2022