Excavation of Lunar Regolith with Large Grains by Rippers for Improved Excavation Efficiency

As human activities expand to the Moon, Mars, and other extraterrestrial bodies, it will be necessary to use local resources rather than bringing everything from Earth. In situ resource utilization (ISRU), or planetary surface engineering, starts with excavation and dirt-moving. The current study focuses on excavation of lunar regolith simulant by blading with and without preripping (mechanical raking) and points out the need for considering the relative proportion of coarse grains in regolith when dealing with excavation force and energy. The coarse-grain content of the lunar regolith, estimated from 11 Apollo cores, can reach 30% by mass. Prior ripping of vibrationally compacted beds of a standard fine regolith simulant can decrease total excavation resistance (when subsequent blading is included) by up to 20% for relative regolith densities greater than 60%. The effect of coarse grains on the response of compacted regolith to excavation was more significant than would be expected in most terrestrial practice. In conclusion, it is suggested that careful matching of excavator design to local coarse-grain content of the lunar regolith needs to be considered in designing a planetary surface engineering architecture.