Building with Regolith

Introduction

Due to the exorbitant expense of transporting material out of the earth’s gravity well, it is apparent that, for any sizable structure, much of the construction material will need to be locally sourced. Use of such material is referred to as in situ resource utilization or ISRU.

One such material that is universally abundant on the moon is the lunar regolith, the unconsolidated debris that is the result of the bombardment of the lunar surface by micrometeorites and solar wind irradiation (Meyer, “NASA Lunar Petrographic Educational Thin Section Set.”) over the billions of years since the Moon’s formation.

Description of Addition:

As a former geologist, I am interested in what research has been done on the potential uses and necessary technologies to utilize this material.

Identified uses of regolith include:

Construction Material ((Mueller, 2017)),

Radiation Shielding (MILLER et al., 2009)

Oxygen Production ((Colozza 2020))

Thermal Insulation ((Akisheva and Gourinat 2021)).

Other identified uses include as a feedstock for industrial processes to refine metals (iron, aluminum, and titanium) and to produce industrial chemicals, such as CaO, which would allow the production of concrete using regolith as matrix and native rock as aggregate. Extraction of water from hydrated minerals would also be feasible.

Discussion

The most discussed use of regolith is as material for the construction of the moon base itself. The simplest use of regolith is simply covering a structure built by some other technique with loose regolith to sufficient depth to provide radiation shielding and thermal insulation for the structure. In general, however, it would be necessary for the processed regolith to serve structural (i.e. load-bearing) material.

Two methods to convert regolith into brick like structures are regolith based concrete (Lin 1985) and sintering of the regolith material (Cox 2023) and (Han et al. 2022).

The composition of lunar regolith varies regionally, with the darker Mare regions deriving from extrusive basaltic lava while the older, highland areas have lighter regolith derived from anorthositic rocks (Papike, Simon, and Laul 1982). All but one of the returned samples of lunar regolith from the Apollo missions were from the younger Mare locations. The single exception, returned by Apollo 16, represented highland regolith from the Descartes region.

Table 9.1 from (Faierson and Logan, n.d.)shows typical compositions for Mare and highland regolith, as well as a NASA simulant of Mare regolith.

Lunar regolith contains all the requisite chemicals for the manufacture of concrete (Lin 1985) although the concentration of CaO would need to be enhanced in order to replicate Portland cement.

Lin suggests a possible lunar habitation structure design as shown in Figure 1.

Figure 1. Proposed three level concrete lunar base.

A company called ‘ICON’ has created a product it calls ‘Lavacrete’ which can be 3D printed into habitat structures. It appears from their website (“Build with Us,” n.d.) that this technology has been successfully employed on earth, and they feel that it will be practical both on the Moon and Mars (icon, n.d.).

Another, perhaps more thoroughly investigated, technology for the use of regolith as a building material is sintering (Han et al. 2022). Sintering (“What Is Sintering? (A Definitive Guide),” n.d.) is the process of forming a solid mass of material through heat and pressure without melting to the point of liquefaction. In addition to serving as a construction material for habitats, the high temperature resistance of sintered regolith makes it useful for landing/launch pads where it would be subject to the high temperatures of rocket exhaust (Mueller 2017).

Methods of sintering regolith differ mainly in the energy source used to heat the material and include focused solar radiation, microwaves, lasers, and electric resistive heating.

Feasibility

The feasibility of the methods discussed vary widely. Some are easily feasible with current technology; some would be feasible given a sufficient supply of power and could be accomplished if fusion power becomes available, and some would require new technologies.

Summary

Both lunar regolith-based cements and sintered lunar regolith would seem to be worthy of further investigation. Both methods should be able to fabricate habitable structures. The ability of both methods to be adapted to additive manufacturing (i.e. 3d printing) is a significant plus.

Microwave sintering of regolith using a localized microwave source (Gatto et al. 2024) may be particularly well adapted to constructing launch/landing pads and roads.

References Cited

Akisheva, Yulia, and Yves Gourinat. 2021. “Utilisation of Moon Regolith for Radiation Protection and Thermal Insulation in Permanent Lunar Habitats.” Applied Sciences 11 (9): 3853. https://doi.org/10.3390/app11093853.

“Build with Us.” n.d. ICON. Accessed March 6, 2024. https://www.iconbuild.com/build-with-us.

Colozza, Anthony J. 2020. “Small Lunar Base Camp and In Situ Resource Utilization Oxygen Production Facility Power System Comparison.” NASA/CR—2020-220368. Vantage Partners, LLC, Brook Park, Ohio.

Cox, Thomas A. 2023. “Investigation into Sintered Lunar Regolith Construction Methods and Novel Usability Evaluation.” https://digitalcommons.library.umaine.edu/etd/3794/.

Faierson, Eric J., and Kathryn V. Logan. n.d. “9 Potential ISRU of Lunar Regolith for Planetary Habitation Applications.” Virginia Polytechnic Institute and State University.

Gatto, Andrea, Silvio Defanti, Elena Bassoli, Alessio Mattioni, Umberto Martini, and Gabriele Incerti. 2024. “Preliminary Study on Localized Microwave Sintering of Lunar Regolith.” Acta Astronautica 218 (May): 126–36. https://doi.org/10.1016/j.actaastro.2024.02.026.

Han, Wenbin, Lieyun Ding, Lixiong Cai, Junjie Zhu, Hanbin Luo, and Tao Tang. 2022. “Sintering of HUST-1 Lunar Regolith Simulant.” Construction and Building Materials 324 (March): 126655. https://doi.org/10.1016/j.conbuildmat.2022.126655.

I CON. n.d. “3D Printing on the Moon and Beyond for NASA | Project Olympus.” Website. https://www.iconbuild.com/media-gallery/3d-printing-on-the-moon-and-beyond-for-nasa-project-olympus.

Lin, T. D. 1985. Concrete for Lunar Base Construction. https://ui.adsabs.harvard.edu/abs/1985lbsa.conf.381L.

Miller, J., et al. 2008. "Radiation shielding properties of lunar regolith and regolith simulant."
LPI Contributions 1415 (2008).

Mueller, Robert P. 2017. “Construction with Regolith.” NASA.

Papike, J. J., S. B. Simon, and J. C. Laul. 1982. “The Lunar Regolith: Chemistry, Mineralogy, and Petrology.” Reviews of Geophysics 20 (4): 761–826. https://doi.org/10.1029/RG020i004p00761.

“What Is Sintering? (A Definitive Guide).” n.d. Accessed March 6, 2024. https://www.twi-global.com/technical-knowledge/faqs/what-is-sintering.aspx.

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