Mechanical properties of lunar surface material

Abstract

This paper contains a review of the information that has been obtained about the mechanical properties of the lunar surface from observations made by the American Surveyor spacecraft. It is shown that for a depth of a few meters the material is granular, having a size grading with 90% below about 250 to 500 μ and 50% below 20 μ. The rock density is about 2.4 to 3.1 g/cm^3. From the imprints of the Surveyor footpads it is deduced that the angle of internal friction of the material is 37° to 39° and the cohesion is in the region 0.05 to 0.1 psi. The bulk density is about 1.5 g/cm^3, indicating a voidage of 0.45. The results are compared with those obtained from observations made by the Russian Luna spacecraft and it is suggested that differences between the two sets of results are due to ambiguities in the Russian estimate of the bulk density of the granular surface.

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