The Development of a Soil for Lunar Surface Mobility Testing in Ambient Conditions

The mechanical properties of the lunar soil are critical parameters in predicting vehicle performance on the Moon. In preparation for Man's return to the Moon, surface vehicles must be tested on terrain that represents the mechanical strength of the lunar ground. Terrain that simulates the lunar trafficability conditions must have similar compaction and shear response underneath the wheel. This paper discusses the development of a soil (called GRC-1) and soil-preparation method to emulate the measured compaction and shear characteristics of the Moon's surface. A semi-empirical design approach was used incorporating particle sieve and hydrometer analyses as well as triaxial strength testing. Soil preparations were developed to match stress-strain curves resulting from in-situ lunar experiments. Additionally, results of laboratory strength tests with returned lunar soil samples and lunar soil simulants were compared to provide insight into the material's relative strength properties.