Robotic drilling tests in simulated lunar regolith environment

Abstract

A deep extraterrestrial drilling mission potentially adds a new level of complexity, and it is crucial to understand the associated challenges. To cope with China'sChang'E 5 mission to return subsurface regolith samples from the Moon, a series of laboratory tests were performed to validate the lunar robotic drilling from 2015 to 2018. The tests took place in a simulated thermal-vacuum regolith environment, a highly relevant lunar analog site. Force and temperature sensors were integrated into a 2-m class dry auger coring drill to assess the mechanical and thermophysical status of the sampling process. The operation of the entire testing system was automated, covering regolith penetration and data collection and storage. The science team used sensing data to characterize the subsurface geologic strata, assess the conditions of the drilling robot, and direct the sampling strategy. This experiment represents an essential first step in understanding the technology and operational requirements for lunar drilling and sampling mission. Many laboratory tests have helped guide the design and implementation of the highly successful lunar regolith-sampling task in the Chang'E 5 mission. This paper documents the experimental system design, highlighting some critical design criteria and design tradeoffs. It also discusses the results of laboratory testing and lists some of the key technological lessons learned.

Robotic drilling for the Chinese Chang’E 5 lunar sample-return mission

“…Most tests can be conducted under normal pressure with a type of LRS to accelerate the iteration process during the prototype design, development, and optimization in the early stages (Shi et al, 2014; Hirshorn et al, 2017). Nevertheless, drilling tests in vacuum chambers are also essential in later stages to validate the vacuum adaptability of the mechatronic system, maximum cutting temperature on the drill bit, and potential shortcomings (Zhang et al 2018, 2021d, 2021b).…”

“…(ii) Low-gravity tests were conducted under simulated low-gravity conditions, either by inclining the drill or replacing the regolith simulant with low-density plastic particles to assess sampling performance under lunar gravity conditions (Tables 4 and 5). (iii) Thermal-vacuum tests were conducted either by placing the entire robotic drill inside or by stretching the drill tool into a vacuum chamber to assess the thermomechanical characteristics of drilling with the LRS or rock simulant in the final stage (Zhang et al, 2021d). The sample was weighed in all tests by removing the soft tube from the retraction mechanism when the sampling was completed.…”

“…The percussion motor was manually started or stopped during drilling. ( f ) Maximum drilling temperature of the drill tool inside the vacuum chamber with the testbed in Zhang et al (2021d). Tests 1–18 were for the regolith simulant and tests 19–20 were for rock simulant when the percussion motor was not utilized.

Figure 16.Thermal-vacuum sensing method.

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Geotechnical and Shear Behavior of Novel Lunar Regolith Simulants TUBS-M, TUBS-T, and TUBS-I

“…For all of these technologies, lunar regolith must be excavated, transported, and processed. Digging [ 57 ] and drilling [ 58 ] are not only important for the sampling process but mandatory for all the above-mentioned technologies. These must be designed and optimized for the materials involved.…”