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Future lunar exploration missions are increasingly targeting the lunar poles, where water ice is believed to exist within permanently shadowed regions. Understanding the mechanical properties of icy lunar regolith under in-situ conditions is critical for the design of rovers, drilling mechanisms, and in-situ resource utilization (ISRU) systems. However, the unique combination of low gravity, high vacuum, and ultra-low temperatures poses significant challenges to geotechnical engineering and ground testing. This paper presents a systematic study focusing on these three typical in-situ environments. It details the development of a specialized lunar extreme environment simulation facility and reports on static cone penetration tests (CPT) conducted on icy lunar soil simulants.
First, to accurately replicate the physical and mechanical characteristics of anorthositic lunar regolith found in the polar regions, a new simulant named CUMT-i was developed. Referencing the physical properties of samples returned by Apollo 16, the dry simulant was prepared using a melt-sintering and crushing method. To mimic the icy regolith, an ice-soil mixture was created through a controlled water-mixing and freezing process. Morphological analysis and characterization demonstrated that by optimizing process parameters, the granular morphological features of the CUMT-i simulant highly reproduce those of the Apollo 16 lunar soil, ensuring the validity of subsequent mechanical tests.
Second, a sophisticated ground simulation facility for extreme lunar environments was developed. Building upon an existing superconducting magnetic levitation device used for gravity compensation, the system was upgraded with integrated high-vacuum and extreme temperature simulation modules. This advanced system achieved long-duration, continuous simulation of a 1/6 g gravity field, an ultimate vacuum of 10−6Pa, and a wide temperature range of -180°C to 180°C within a Φ500×500 mm experimental space. This platform effectively recreates the in-situ occurrence characteristics of the icy lunar soil layer, laying a solid foundation for conducting CPT under realistic environmental conditions.
Third, static cone penetration tests were conducted on the icy CUMT-i simulant under these simulated in-situ environments. The study quantitatively revealed the influence of ice content, dry density, penetration rate, and cone tip angle on penetration resistance. The results indicate that: (1) Penetration resistance increases with ice content, although the rate of increase gradually diminishes as the ice content rises. (2) Both penetration resistance and normalized penetration resistance increase with higher dry density, faster penetration rates, and larger cone tip angles. (3) An increase in penetration rate leads to a significant rise in peak penetration resistance and the corresponding penetration depth. (4) Conversely, increasing the cone tip angle results in a significant reduction in the penetration depth corresponding to the peak resistance, as well as a decrease in the critical normalized penetration depth.
This research provides crucial experimental data and theoretical insights into the interaction between probing devices and icy regolith in extreme lunar environments.
| Country | China |
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