Abrasion between Rotary Shaft/Seal Pairs under Extremes of Lunar Highland Regolith Exposure

Abstract:

This study investigates the abrasive effects of Lunar Highland regolith simulant (TH100) and the particle size effect on stainless steel/PTFE rotary shaft–lip seal assemblies. A custom-built sand-pot testing rig filled with Nitrogen gas was used to expose EN-1.4404 stainless steel shafts paired with spring-loaded natural PTFE seals to fine (≤0.125 mm) and coarse (1.400–2.000 mm) Lunar Highland regolith particles. Each rotating pair was operated for 0.25, 0.5, and 24 hours at sequential shaft positions. Wear progression was assessed through shaft surface roughness measurements and scanning electron microscopy of the seals before and after testing. All tests under fine particles were completed without failure, whereas the sealing system exposed to coarse particles failed during the final shaft position and test was stopped. Fine particles primarily induced micro-cutting on the shaft surface, while coarse particles produced a combination of micro-cutting and micro-ploughing. These findings reveal the pronounced influence of particle size on wear mechanisms in lunar dust-exposed rotary sealing systems, with implications for the durability of moving components in extraterrestrial environments.

• Periodical: Key Engineering Materials (Volume 1061)
• Pages: 33-43
• DOI: https://doi.org/10.4028/p-Uyt4GK
• Online since: August 2026
• Authors: Bahram Turapov*, Gabor Kalacska, Róbert Keresztes
• Keywords: Lunar Highland Regolith, Particle Size Effect, Sealing System, Shaft Surface, Wear

References

[1] Md. Abdullah, M. S. H. Motayed, and M. A. S. I. Albaruni, "Advancements in Tribology and Their Impact on Space Systems: A Review," J Bio Tribocorros, vol. 11, no. 4, p.123, Dec. 2025.

DOI: 10.1007/s40735-025-01047-z

[2] R. L. Kobrick, D. M. Klaus, and K. W. Street, "Defining an abrasion index for lunar surface systems as a function of dust interaction modes and variable concentration zones," Planet Space Sci, vol. 59, no. 14, p.1749–1757, Nov. 2011.

DOI: 10.1016/j.pss.2010.10.010

[3] J. E. Colwell, S. Batiste, M. Horányi, S. Robertson, and S. Sture, "Lunar surface: Dust dynamics and regolith mechanics," Reviews of Geophysics, vol. 45, no. 2, Jun. 2007.

DOI: 10.1029/2005RG000184

[4] S. Noble, "The Lunar Regolith," MSFC-2221, Mar. 2009.

[5] B. Turapov, G. Kalacska, and R. Keresztes, "Establishing a Tribo-System to Study the Frictional Effects of Lunar Regolith," Defect and Diffusion Forum, vol. 443, p.117–123, Jun. 2025.

DOI: 10.4028/p-It6tsL

[6] G. Kalácska et al., "The Abrasive Effect of Moon and Mars Regolith Simulants on Stainless Steel Rotating Shaft and Polytetrafluoroethylene Sealing Material Pairs," Materials, vol. 17, no. 17, p.4240, Aug. 2024.

DOI: 10.3390/ma17174240

[7] K. Matsumoto et al., "Application of collar seals for bearings in the lunar exploration rover," Tribology Online, vol. 15, no. 5, p.332–342, 2020.

DOI: 10.2474/TROL.15.332

[8] G. Kalácska, G. Barkó, T. Bálint, R. Keresztes, L. Székely, and Z. Károly, "Tribological Effects of Martian Regoliths on Stainless Steel with Natural and Composite Lip Seal and Packing Materials," Lubricants, vol. 13, no. 4, p.136, Mar. 2025.

DOI: 10.3390/lubricants13040136

[9] J. Tan, N. Melkoumian, D. Harvey, and R. Akmeliawati, "Lunarminer Framework for Nature-Inspired Swarm Robotics in Lunar Water Ice Extraction," Biomimetics, vol. 9, no. 11, p.680, Nov. 2024.

DOI: 10.3390/biomimetics9110680

[10] J. Sorrell, E. E. Nunez, and A. A. Polycarpou, "High-performance polymer composites for dust-tolerant extreme environment bearings for lunar exploration," Wear, vol. 574–575, p.206084, Jul. 2025.

DOI: 10.1016/j.wear.2025.206084

[11] K. Matsumoto, K. Yanagase, and S. Takada, "Study of PEEK composite for sliding mechanisms in space environment," Tribol Int, vol. 212, p.110947, Dec. 2025.

DOI: 10.1016/j.triboint.2025.110947

[12] Bahram Turapov and Gábor Kalácska, "Dust-Proofing on the Moon: A Review of Mechanical Seals for Lunar Settlement Sustainability," Mechanical Engineering Letters, vol. 25, p.47–58, 2024.

[13] I. R. H. M. J. Delgado, "Preliminary Assessment of Seals for Dust Mitigation of Mechanical Components for Lunar Surface Systems," 2010. [Online]. Available: http://www.sti.nasa.gov.

[14] G. Barkó, G. Kalácska, R. Keresztes, L. Zsidai, H. Shegawu, and Á. Kalácska, "Abrasion Evaluation of Moon and Mars Simulants on Rotating Shaft/Sealing Materials: Simulants and Structural Materials Review and Selection," Aug. 01, 2023, Multidisciplinary Digital Publishing Institute (MDPI).

DOI: 10.3390/lubricants11080334

[15] Bahram Turapov, Gábor Kalácska, and Róbert Keresztes, "Experimental Set-up of Sand-Pot Device for 3-Body Abrasive Wear Testing," Mechanical Engineering Letters, vol. 26, p.76–85, 2025.