Simulation of the Lunar Environment for the Study of Regolith Strength

For the return of humans to the lunar surface, there is need for a more comprehensive understanding of the strength properties of the lunar regolith in order to reduce risk to the explorers. Spacecraft will land on, shelters and bases will be constructed in, materials will be mined from, and exploration vehicles will traverse extensive regions of the undisturbed lunar regolith. Previous lunar missions included soil mechanics studies, but did not provide sufficient information to estimate regolith strength in unexplored regions of the Moon. This paper describes the design of a system to measure the strength characteristics of lunar soil simulants in an analog lunar environment. In this system, the simulant is tested in high vacuum to replicate the ambient pressure experienced by lunar regolith particles. Within the vacuum chamber, soil samples reside in a copper bin that can be heated or reduced to near liquid nitrogen temperature using a temperature controlled contact plate. While monitoring chamber pressure and simulant temperature, the strength of the regolith simulant is analyzed by means of an externally driven bevameter device capable of performing plate-sinkage, cone penetration, and annular shear tests within the vacuum chamber. Principles of similitude are applied to account for the effects of gravity. The design of the lunar environment simulation chamber and initial strength testing experiments are discussed. Additionally, the application of this system to lunar regolith strength characteristic prediction of previously unexplored regions of the Moon is examined.