Lunar surface mechanical properties from Surveyor data.

Abstract

During the Surveyor program spacecraft were successfully landed at five widely separated lunar locations. Recent computer simulations of each landing have provided more comprehensive data on the mechanical properties of the lunar surface than have been obtained previously by this method of analysis. Results show that the variations in surface bearing pressure observed at the various lunar sites are probably due to surface slope effects and do not necessarily indicate differences in soil properties at these sites. Estimates of cohesion at two sites give almost identical results and further support the conclusion that the soil properties at all sites are probably very similar. Surface pressures that resist horizontal (plowing) motion are largely due to cohesion, and density and gravitational contributions are small. It is concluded that the lunar surface bearing strength is essentially zero at the surface and, for zero surface slope, increases with penetration depth at a rate of 1.87 (plus or minus 0.33) N/cu cm. The cohesion of the lunar soil is estimated to be between 0.11 and 0.17 N/sq cm.