Design, test, and verification of in-situ condition preserved coring and analysis system in lunar-based simulation environment

Abstract

The lunar surface and its deep layers contain abundant resources and valuable information resources, the exploration and exploitation of which are important for the sustainable development of the human economy and society. Technological exploration and research in the field of deep space science, especially lunar-based exploration, is a scientific strategy that has been pursued in China and worldwide. Drilling and sampling are key to accurate exploration of the desirable characteristics of deep lunar resources. In this study, an in-situ condition preserved coring (ICP-Coring) and analysis system, which can be used to test drilling tools and develop effective sampling strategies, was designed. The key features of the system include: (1) capability to replicate the extreme temperature fluctuations of the lunar environment (−185 to 200 °C) with intelligent temperature control; (2) ability to maintain a vacuum environment at a scale of 10−3 Pa, both under unloaded conditions within a ϕ580 mm × 1000 mm test chamber, and under loaded conditions using a ϕ400 mm × 800 mm lunar rock simulant; (3) application of axial pressures up to 4 MPa and confining pressures up to 3.5 MPa; (4) sample rotation at any angle with a maximum sampling length of 800 mm; and (5) multiple modes of rotary-percussive drilling, controlled by penetration speed and weight on bit (WOB). Experimental studies on the drilling characteristics in the lunar rock simulant-loaded state under different drill bit-percussive-vacuum environment configurations were conducted. The results show that the outgassing rate of the lunar soil simulant is greater than that of the lunar rock simulant and that a low-temperature environment contributes to a reduced vacuum of the lunar-based simulated environment. The rotary-percussive drilling method effectively shortens the sampling time. With increasing sampling depth, the temperature rise of the drilling tools tends to rapidly increase, followed by slow growth or steady fluctuations. The temperature rise energy accumulation of the drill bits under vacuum is more significant than that under atmospheric pressure, approximately 1.47 times higher. The real-time monitored drilling pressure, penetration speed and rotary torque during drilling serve as parameters for discriminating the drilling status. The results of this research can provide a scientific basis for returning samples from lunar rock in extreme lunar-based environments.