Construction Scheme And Mechanical Performance Of Lunar Structures With Regolith Bag

Lunar construction is one of the focuses of lunar exploration.Due to the harsh environment and limited resources on the Moon,construction activities are faced with many challenges and environmental problems such as low gravity,ultra-vacuum condition,strong radiation,large temperature difference,lunar dust and resources constraints of materials and energy.Therefore,the technical route of in-situ and automation is recommended to be adopted in the structural construction process.In this thesis,to meet the needs of the construction demands of the International Lunar Research Station,the environmental and resource conditions on the Moon were reviewed and investigated,and a regolith bag structure form was proposed.The high-performance fibre bag is adopted to fill with the lunar regolith,which is built by the mechanical arms to form structure.Regolith bag structure has significant advantages in lunar environment considering its high utilisation rate of in-situ resources and high unmanned degree in construction process.In this study,material selection,structural form and construction method were defined,and construction scheme of the lunar standard unit based on the regolith bag was proposed as well.The main work and achievements are as follows:(1)The environmental and resource conditions on the Moon were investigated and analysed.According to the special conditions of the lunar surface,the environmental characteristics,structural impact and countermeasures to those challenges were clarified.Considering that the internal pressure of lunar building is much greater than gravity load,the requirements of the structural tension and sealing performance have significantly increased,which leads to essential differences of the structural system and construction method applied between the Moon and the Earth.With the support of the Chang’e 5 lunar sample of Tsinghua University,systematic investigation was carried out on in-situ resources to clarify the mechanical properties of the lunar soil,and the differences between the earth soil and lunar soil and the reasons for that.The lunar soil has a sharp grain shape under the effect of space weathering and shows abnormally high shear strength in the ultra-vacuum environment on lunar surface.In addition,lunar soil is widely distributed,loosely accumulated,and easy to collect and process for construction.The lunar soil solidification is a necessary measure to integrate in-situ resources and prevent the problem of lunar dust.(2)The simulation effect of CUG-1A lunar soil simulant was investigated through experiments.It is proved that the composition,specific gravity,particle size distribution and compressive properties of lunar soil were well simulated by the CUG lunar soil simulant,while the shear strength of the simulant was lower compared with the real lunar soil,which may be due to the differences of weathering conditions and the experimental environment differences between the Moon and the Earth.(3)The properties of fabric material were experimentally studied through tensile tests and vacuum aging tests.Kevlar had excellent tensile properties,while the elongation of Vectran and polyethylene fabric was too large for application.Due to the abrasion between fibres,elastic modulus and tensile strength were reduced around 10% in vacuum environment.Nevertheless,vacuum environment had little effect on the elongation.(4)The compression performance of regolith bag components was studied by the uniaxial compression tests.The equivalent solidification strength of lunar soil reached 6.9MPa,which met the requirement of lunar construction.Methods of increasing the filling rate and applying external constraints can increase the initial compactness and improve the filling effect,making the lunar regolith to be uniformly compacted and co-stressed with the restraint belts to delay the end damage.(5)The construction scheme of the standard unit for the lunar structure based on the regolith bag was proposed.Aiming at the development goals of the fourth phase of the lunar exploration project,the common needs and requirements of the lunar surface construction were identified and analysed in this thesis.For the lunar standard unit of the regolith bag structure,the material selection,structural form and construction method were clarified.Accordingly,the structural checking calculation and experiment verification of the construction scheme were carried out,and the scheme was evaluated based on the in-situ resource utilization rate,working loads and other indicators.Overall,the research in this thesis provides the theoretical basis and technical support for the application of the regolith bag structure in lunar construction.