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Soil Mechanics

NSSDCA ID: 1971-063C-02

Mission Name: Apollo 15 Lunar Module /ALSEP
Principal Investigator:Prof. James K. Mitchell

Description

The soil mechanics experiment was designed to obtain data on the characteristics and mechanical behavior of the lunar soil at the surface and subsurface and the variation of these properties in a lateral direction. Additional objectives were to aid in the interpretation of data obtained from other surface activities and experiments and to develop lunar surface models to help in the solution of engineering properties associated with future lunar exploration. The equipment for the experiment included a sampling scoop, a self-recording penetrometer with interchangeable load plate and cones of various diameters, core tubes, and the Apollo lunar surface drill. From lunar samples (such as core tube samples and other geological samples, especially the fine-grained soil samples) obtained by the lunar geology experiment, further soil mechanics data was derived by testing in the Lunar Receiving Laboratory (LRL). The photographic equipment used for this experiment included a battery-operated 16-mm Maurer data acquisition camera (10-mm lens) and a Hasselblad electric data camera (60-mm lens). Television was also used in a real-time support role. The astronauts performed the required trenching activities, penetrometer load plate and cone tests, and soil behavior characteristics observations in the Hadley-Apennine area.

The Lunar Self-Recording Penetrometer (LSRP) had a mass of 2.3 kg and consisted of an upper cannister housing attached to the top of a long shaft and a reference pad assembly attached to the bottom. A recording drum was contained in the upper cannister and captured a record of each penetration. The LSRP was equipped with a 2.54 x 12.7 cm bearing plate and three penetrating cones with base areas of 1.29, 3.22, and 6.45 square cm and a 30 degree apex angle that could be attached to the bottom of the penetration shaft at the reference pad. The reference pad, which folded for storage, acted as a datum on the lunar surface for measurement of penetration depth. When an astronaut pushed on the upper end, the bearing plate or lower cone and shaft would penetrate into the lunar soil while the reference pad stayed on the surface. A retractor cable mechanism running from the reference pad to the upper housing actuated a stylus which would move axially along the recording drum to measure the depth of penetration. The force applied through the extension handle by the astronaut would deflect a calibrated coil spring which would cause the recording drum to rotate under the stylus by an amount prportional to the force. The maximum force caused a 30 degree rotation. The LSRP had a maximum penetration depth of 76 cm and the ability to measure penetration force to a maximum of 111 N.

The core tubes were thin-walled hollow aluminum tubes, 37.5 cm long with an inside diameter of 4.13 cm and an outside diameter of 4.38 cm. The lower tubes could be used individually or screwed together with an upper tube to make a longer, or double, tube. The lower tube had a stainles steel bit on the bottom for penetrating the soil. A "keeper", a flat disk with the same inside diameter as the tube, fit inside the top end of the tube and an adapter was screwed on top. The tubes would be driven into the ground with a hammer as far as they could go. Then the keeper would be pushed down inside the tube by a long rod which fit into a hole in the top of the adapter. The keeper would be pushed to the top of the sample in order to keep the sample in place. The tube was then removed from the ground, the end coverd with a teflon cap, and the sample was brought back to Earth for analysis.

The Apollo lunar surface drill consisted of an electric drill with a set of long hollow bore stems which could be screwed together. The top of the drill had a battery pack and handle, directly underneath this was a power head and thermal shield. The drill stem extended from this through a treadle placed on the surface and into the regolith. At the bottom of the first drill stem was a 6 cm long drill bit with five tungsten-carbide blades. The drill was used to retrieve deep samples (down to 4.6 meters) of lunar regolith.

On the Apollo 15 mission, one soil trench was excavated at the ALSEP site with a near-vertical face of approximately 28 cm and another at station 6. The self-recording penetrometer was used near the ALSEP site for four cone penetration tests and two plate load tests. The core tubes were used in three locations to collect a total sample of 3302 grams. A single tube was used at station 6 and two double tubes were used at stations 2 and 9A. A drill hole sample was taken on the second EVA near the ALSEP site.

Alternate Names

  • Apollo15ALSEP/SoilMechanics
  • S200

Discipline

  • Planetary Science: Geology and Geophysics

Additional Information

Questions and comments about this experiment can be directed to: Dr. David R. Williams

 

Personnel

NameRoleOriginal AffiliationE-mail
Mr. D. CarrierOther InvestigatorNASA Johnson Space Center
Mr. Nicholas C. CostesOther InvestigatorNASA Johnson Space Center
Dr. Leilie G. BromwellOther InvestigatorMassachusetts Institute of Technologylbromwell@bcieng.com
Prof. James K. MitchellPrincipal InvestigatorUniversity of California, Berkeley

Selected References

  • Mitchell, J. K., et al., Soil mechanics experiment, in Apollo 15 Prelim. Sci. Rept., SP-289, 7-1 to 7-28, NASA-GSFC, Wash., DC, 1972.
  • Costes, N. C., et al., Cone penetration resistance test --- an approach to evaluating in-place strength and packing characteristics of lunar soils, Proc. Second Lunar Sci. Conf., 3, 1973-1987, M.I.T. Press, 1971.

Related Information at NSSDCA

Model of LSRP

Model of the Lunar Surface Recording Penetrometer (LSRP) at the National Air and Space Museum

Apollo 16 Soil Mechanics Experiment

Scanned Penetometer Data On-line (Lunar Data Project)

Lunar Data Project Apollo Home Page

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