In-space resource utilization is something I’ve been fascinated by, and exploring in an academic fashion, for a very long time, almost as long as I’ve been interested in space. Today, I’m sharing a brief essay I wrote on the importance of regolith use for establishing a durable human presence on the Moon. It was originally written as something tangentially related to my “real” job. I hope you find this interesting – it is part of an effort I intend to make going forward to include more rigorous, “academic” material for these Tuesday posts. Not all will be scientific or pertaining to space, but given my preoccupations and occupation, those topics are likely to be frequent.

Space resource utilization[1] is not new, beginning with the United States’ Project SCORE (Signal Communications by Orbital Relay Equipment) in December 1958, which leveraged the orbital environment to provide a communication relay between distant ground stations [1] [2].  Communication remains the largest use of space [3] [4].  Reduced launch costs, renewed interest in sustained presence, and international competition are presently driving renewed interest in space material resource utilization.  Structural materials like regolith should be prioritized, followed by water from which both propellant and life support can be derived.  These constitute the major mass requirements of most space mission profiles; by fulfilling these needs in-situ, logistics and costs are reduced.

Regolith[2] is abundant and accessible; on the Moon, it is so abundant its handling and mitigation are key considerations for manned and unmanned missions [5].  This makes it a logical target for early in-situ resource utilization (ISRU).  Regolith, through technologies from “sandbags” to laser sintering, can be repurposed for radiation shielding, habitats, landing pads, et cetera [5] [6] [7].  Some applications, like radiation shielding and habitats, are relevant to manned missions; others, like landing pads and other infrastructure, are valuable to manned and robotic missions.  Meeting infrastructure needs through ISRU dramatically reduces launch demands and increases sustainability of presence.  Additionally, experience processing and interacting with regolith is a key enabler of more complex technologies for propellant extraction.

Propellant[3] is the primary consumable on space missions.  Launch vehicles have high propellant mass ratios[4]; the Falcon Heavy achieves mass fraction of 0.966, and spacecraft have mass fractions of .33 or greater [8] [9].  Traditional space mission design defines end-of-life based on fuel expenditure.  The option to extend range with in-situ propellant, rather than terrestrially launched, opens new mission profiles – a major impediment to the Mars Sample Return (MSR) program is the need for enough fuel to reach the Martian surface and take off again [10] [11] [12].  Thus, propellant is an attractive resource to derive in-situ, hydrolox[5] being the obvious option given the suspected abundance of both elements as water [10] [13] [14] [15].  Beyond-cislunar mission profiles particularly benefit from refueling, and the benefit is acute for profiles landing on another body and launching again.

ISRU will enable a paradigm shift in space mission design, reducing the current size, weight, and power (SWaP) constraints.  As ISRU proliferates, potential customers for space resources will expand to include most users of the domain, from routine satellite operators servicing terrestrial users to scientific missions throughout the solar system.  Regolith is a logical first target; leveraging it will reduce the amount of heavy infrastructure that must be transported from Earth’s surface.  Water should be the next target due to its utility as both propellant and life support.  From this foundation, future missions will be postured to explore and utilize other resources we discover in our expanded bailiwick.

[1] Here referring to practical, non-scientific use of space’s resources, whether material or otherwise.

[2] Regolith is a geological term referring to the layer of loose, nonorganic material which covers most celestial bodies and parts of the Earth

[3] The term “propellant” is used instead of fuel in most cases because it refers to both the fuel component and the oxidizer.

[4] Mass ratios typically compare the mass of propellant (fuel and oxidizer) to the wet mass (meaning the fueled mass) of the vehicle in question.  Orbital launch vehicles require high mass ratios in order to achieve the velocities required for orbital flight (about 8 km/s ).

[5] Hydrolox refers to liquid hydrogen and liquid oxygen, where liquid hydrogen is the fuel, and liquid oxygen is the oxidizer.  Despite difficulties relating to management of cryogenic fluids, hydrolox is widely perceived as the optimal chemical propellant that can be derived in situ.

References

[1]National Air and Space Museum, “Communications Satellite, SCORE,” Smithsonian Institute, Washington, DC.
[2]APPEL News Staff, “This Month in NASA History: The U.S. SCORE’d in the Race to Space,” NASA APPEL Knowledge Services, Washington, DC, 2015.
[3]The Editors of Encylopaedia Britannica, “Telstar,” Encyclopaedia Britannica, Inc., 10 July 2025. [Online]. Available: https://www.britannica.com/technology/Telstar-communications-satellite. [Accessed 6 September 2025].
[4]United Nations Office for Outer Space Affairs, “Outer Space Objects Index,” Vienna, 2025.
[5]K. M. Cannon, C. B. Dreyer, G. F. Sowers, J. Schmit, T. Nguyen, K. Sanny and J. Schertz, “Working with lunar surface materials: Review and analysis of dust mitigation and regolith conveyance technologies,” Acta Astronautica, vol. 196, pp. 259-274, July 2022.
[6]S. Moazen, F. Gosselin, I. Tabiai and M. Dube, “3D printing LDPE/lunar regolith simulant composite: manufacturing with in-situ resources on the Moon,” Acta Astronautica, Vols. In Press, Journal Pre-proof, 2 September 2025.
[7]G. Just, “Investigation and development of regolith excavation and handling mechanisms for lunar in-situ resource utilisation,” The University of Manchester, Manchester, 2021.
[8]M. W. Gerberich and S. R. Oleson, “Estimation Model of Spacecraft Parameters and Cost Based on a Statistical Analysis of COMPASS Designs,” NASA Technical Reports, pp. 1-10, 2014.
[9]Office of Safety and Mission Assurance, “Space Launch Report: SpaceX Falcon 9 Data Sheet,” National Aeronautics and Space Administration, Washington, DC, 2017.
[10]J. A. Hoffman, M. H. Hecht, D. Rapp, J. J. Hartvigsen, J. G. Soohoo, A. M. Aboobaker, J. B. Mcclean, A. M. Liu, E. D. Hinterman, M. Nasr, S. Hariharan, K. J. Horn, F. E. Meyen, H. Okkels and P. Steen, “Mars Oxygen ISRU Experiment (MOXIE) – Preparing for human Mars exploration,” Science Advances, vol. 8, no. 35, 31 August 2022.
[11]D. L. Linne, “A Rocket Engine for Mars sample Return Using In Situ Propellants,” in Aerospace Sciences Meeting and Exhibit, Reno, 1997.
[12]R. Zubrin, “A Comparison of Methods for the Mars Sample Return Mission,” Pioneer Astronautics, pp. 1-7, 1996.
[13]W. Notardonato, W. Johnson, A. Swanger and W. McQuade, “In-Space Propellant Production Using Water,” NASA Technical Reports, pp. 1-11, 2012.
[14]S. E. Gallucci, M. M. Micci and S. G. Bilen, “Design of a Water-Propellant 17.8-GHz Microwave Electrothermal Thruster,” in International Electric Propulsion Conference, Atlanta, 2017.
[15]D. Ferrara, P. Cicconi, A. Minotti, M. Trovato, M. Amicarelli and A. C. Caputo, “A design framework for the development of an innovative water-electrolysis space propulsion system,” in Procedia CIRP, Patras, 2025.
[16]J. Cilliers, K. Hadler and J. Rasera, “Toward the utilization of resources in space: knowledge gaps, open questions, and priorities,” NPJ: Microgravity, vol. 9, no. 22, 25 March 2023.
[17]A. Meurisse and J. Carpenter, “Past, present and future rationale for space resource utilisation,” Planetary and Space Science, vol. 182, March 2020.

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