Lunar surface mechanical properties at the landing site of Surveyor 3

Abstract

Analyses of engineering and television data returned by Surveyor 3 indicate that the mechanical properties of the lunar surface material inside the crater in which the spacecraft landed are similar to the mechanical properties of the level mare area at the Surveyor 1 landing site. The static bearing strength ranges from 2 to 6 newtons/cm2 for a penetration depth between 2 and 5 cm and a bearing diameter between 20 and 30 cm. The soil cohesion is less than 1 newton/cm2; its rigidity modulus is low. A substantial percentage of the particles of the lunar surface material appear to be smaller than 0.06 mm in diameter, and a significant number are under 0.01 mm. The fine structure of the surface can be deformed substantially by applying a small, distributed, compressive force.

Lunar surface mechanical properties from Surveyor data

“…Choate et al [1968b] and others have pointed out that force levels are relatively insensitive to surface strength over the range of strengths (3-7 N/cm 2 average with depth) that yields simulated surface penetrations lying within the range of penetrations measured from TV data. The degree of correlation between analytical and measured force histories (e.g., maximum force levels agree within about 10%; initial footpad impact times agree within 10 msec) shown by Christensen et al [1967Christensen et al [ , 1968a, c], Choate et al [1968a, b], and Sperling and Garba [1967] is typical of the correlation achieved in the present analysis. Therefore additional force comparison will not be presented here.…”

“…The analyses and tests performed during landing gear-design and development, as well as those performed to establish landing performance capability, are described by Deitrick and Jones [1963] and by the Surveyor Final Engineering Report [1968]. The complex mathematical models that were used for design purposes have also been used to simulate the achieved lunar landings, which are described by Christensen et al [1967Christensen et al [ , 1968a and Choate et al [1968a]. These simulations and those by Sperling and Garba [1967] permit the estimation (summarized by Choate et al [1968b]) of lunar surface bearing strength characteristics at each landing site.…”

Theoretical and discrete element simulation studies of aircraft landing impact

“…Over the years, multiple spacecrafts have failed because of landing impact, with the main causes of failure including failure of a control device and structural damage or breach. The methods of soft landing to decrease the landing impact mainly include the use of airbags in Mars 96 [1], the mechanical support structure in Surveyor 3 [2], and the legged lander [3][4][5] (shown in Fig. 1).…”

Properties of Lunar Surface Material From Direct Observation by Spacecraft—Summary*

“…the bulk density of the fine matrix material were made primarily through observations of its response to mechanical loading. The bearing capacity at various depths and bearing diameters and the deformation characteristics point to a bulk density near 1 g/cm a for the top few milli-material took excellent imprints of ridges about 60 •m high on the bottom of a footpad[Christensen et al, 1968b]. This implies that a considerable portion of the material is much finer than 60 t•m.…”