Lunar Excavation Experiments in Simulant Soil Test Beds: Revisiting the Surveyor Geotechnical Data

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Lunar Excavation Experiments in Simulant Soil Test Beds: Revisiting the Surveyor Geotechnical Data

Agui, J. H. / Bucek, M. / DeGennaro, A. / Wilkinson, R. A. / Zeng, X.

Abstract

The establishment of permanent bases on planetary surfaces is an important long-term goal of the space community. Understanding the geotechnical properties of planetary surfaces and their interaction with tools and implements will be essential in addressing the challenges of material-handling equipment for infrastructure development during surface missions. With this aim, a replica of the soil mechanics surface sampler, an extendable scoop with a bearing plate attachment, operated on some of the lunar Surveyor missions in the 1960s, was fabricated and used in a series of simulated bearing and excavation tests. Initially, a set of tests was performed on a small laboratory test stand using an acrylic soil bin with a $30.5 × 33.0 - cm$ footprint. Subsequent tests were performed in a new large-scale soil bin facility ( $2.27 × 5.94 × 0.76 m$ ) to minimize wall effects. Both test setups involved the use of JSC-1a lunar simulant soil beds and motorized actuators to drive the scoop into the simulant. Emphasis was placed on methods of repeatable soil bin preparation. The scoop was attached to a commercial six-axis load cell that provided time-resolved measurements of the three-dimensional forces and torques. In addition, simultaneous video provided detailed imaging of the flow behavior and surcharge formation of the regolith during excavation. A surface-profiling technique was developed to resolve the surface deformation as the scoop penetrated and trenched the simulant. Bearing test data in loose bed preparations in both bins compared well with the Surveyor flight data. The data also included the soil response under compacted soil conditions.