On Modeling Drilling Load in Lunar Regolith Simulant

Drilling and coring, as effective ways to obtain lunar regolith along the longitudinal direction, are widely applied in the lunar sampling field. Conventionally, modeling of drill-soil interaction was divided into soil cutting and screw conveyance processes, ignoring the differences in soil mechanical properties between them. To improve the modeling accuracy, a hypothesis that divides the drill-soil interaction into four parts: cuttings screw conveyance, cuttings extruding, cuttings bulldozing, and in situ simulant cutting, is proposed to establish a novel model based on the passive earth pressure theory. An iterative numerical calculation method is developed to predict the drilling loads. A drilling and coring testbed is developed to conduct experimental tests. Drilling experiments indicate that the drilling loads calculated by the proposed model match well the experimental results. The proposed research provides the instructions to adopt a suitable drilling strategy to match the rotary and penetrating motions, to increase the safety and reliability of drilling control in lunar sampling missions.

Printability and hardening performance of three-dimensionally-printed geopolymer based on lunar regolith simulant for automated construction of lunar infrastructure

Using an in situ lunar regolith as a construction material in combination with 3D printing not only reduces the weight of materials carried from the Earth but also improves the automation of lunar infrastructure construction.This study aims to improve the printability of a geopolymer based on a BH-1 lunar regolith simulant,including the extrudability,open time,and buildability,by controlling the temperature and adding admixtures.Rheological parameters were used to represent printability with different water-to-binder ratios,printing temperatures,and contents of additives.The mechanical properties of the hardening geopolymer with different filling paths and loading directions were tested.The results show that heating the printed filaments with a water-to-binder ratio of 0.32 at 80°C can adjust the printability without adding any additive,which can reduce the construction cost of lunar infrastructure.The printability of the BH-1 geopolymer can also be improved by adding 0.3%Attagel-50 and 0.5%polypropylene fiber by mass at a temperature of 20℃to cope with the changeable environmental conditions on the Moon.After curing under a simulated lunar environment,the 72-h flexural and compressive strengths of the geopolymer specimens reach 4.1 and 48.1 MPa,respectively,which are promising considering that the acceleration of gravity on the Moon is 1/6 of that on the Earth.

3D-printed Lunar regolith simulant-based geopolymer composites with bio-inspired sandwich architectures

Over time,natural materials have evolved to be lightweight,high-strength,tough,and damage-tolerant due to their unique biological structures.Therefore,combining biological inspiration and structural design would provide traditional materials with a broader range of performance and applications.Here,the application of an ink-based three-dimensional(3D)printing strategy to the structural design of a Lunar regolith simulant-based geopolymer(HIT-LRS-1 GP)was first reported,and high-precision carbon fiber/quartz sand-reinforced biomimetic patterns inspired by the cellular sandwich structure of plant stems were fabricated.This study demonstrated how different cellular sandwich structures can balance the structure–property relationship and how to achieve unprecedented damage tolerance for a geopolymer composite.The results presented that components based on these biomimetic architectures exhibited stable non-catastrophic fracture characteristics regardless of the compression direction,and each structure possessed effective damage tolerance and anisotropy of mechanical properties.The results showed that the compressive strengths of honeycomb sandwich patterns,triangular sandwich patterns,wave sandwich patterns,and rectangular sandwich patterns in the Y-axis(Z-axis)direction were 15.6,17.9,11.3,and 20.1 MPa(46.7,26.5,23.8,and 34.4 MPa),respectively,and the maximum fracture strain corresponding to the above four structures could reach 10.2%,6.7%,5.8%,and 5.9%(12.1%,13.7%,13.6%,and 13.9%),respectively.

Synthesis and characterization of geopolymer from lunar regolith simulant based on natural volcanic scoria

In this study,a new GVS(Ground Volcanic Scoria)lunar regolith simulant was produced.The similarity between GVS and lunar soil was proved by comparison with Apollo lunar soil samples and other commercial lunar soil simulants.Then,GVS lunar regolith simulant was investigated as the source material for preparing geopolymer to produce building material for lunar colony construction.To study the possibility of preparing geopolymer from GVS lunar regolith simulant and the optimum activator formulation as well as the optimum curing conditions,alkaline activated GVS slurries with different mixing ratios based on an orthogonal test scheme were prepared.The geopolymer products based on GVS were characterized by flexural strength test,compressive strength test,X-ray fluorescence(XRF),X-ray diffraction(XRD),Fourier Transform Infrared Spectroscopy(FTIR),Scanning Electron Microscope coupled with Energy Dispersive Spectroscopy(SEM-EDS),29Si magic angle spinning-nuclear magnetic resonance(29Si MAS-NMR),and 27Al MAS-NMR.The experimental results indicate that changes in the mass ratio of sodium hydroxide and GVS and curing temperature have the most significant influence on the flexural strength and compressive strength,respectively.The GVS-based geopolymer can obtain the highest 28-day compressive strength and 28-day flexural strength up to 75.6 MPa and 6.3 MPa.Microstructural results imply that the changes of Si occurring in a variety of environments that explaining preliminarily about the reaction mechanism of GVS-based geopolymer.This study approves the feasibility of making a geopolymer derived from the GVS lunar regolith simulant and the potential utilization of geopolymer based on lunar regolith for construction of the lunar colony in future space exploration.