The figure illustrates various aspects of a proposed mechanism that would be mounted in an instrumented penetrator dart for use in acquiring a sample of soil. In operation, the dart would be dropped from a height to make it penetrate the ground to a suitable depth, then the mechanism would be activated to acquire the sample of soil through the side of the dart. The mechanism and dart would be built to withstand a ground-impact deceleration of as much as 30,000 times the acceleration of normal Earth gravity. The mechanism would be able to take a sample of relatively hard, frozen soil at a temperature as low as -80 °C. Originally designed for use in remotely controlled exploration of Mars, the penetrator and mechanism might be adaptable to sampling soil in remote, cold, or otherwise hostile or inaccessible environments on Earth.

The mechanism would include an auger with its axis perpendicular to that of the dart. During transport and impact, the auger would remain stowed within the dart. During the sample-acquisition process, the auger would be pushed out from the dart and turned, thereby boring a side hole and drawing soil into the dart for sampling.

The Entire Mechanism Would Fit within the penetrator dart.

A brushless dc motor would be coupled through a right-angle bevel-gear drive to a shaft for turning the auger. The auger would be free to slide axially along the shaft, but a square spline would constrain the auger to rotate with the shaft. The auger would be spring-loaded toward extension, but prior to use, it would be restrained against extension by engagement between mating threads on the auger and an interior structural component of the dart.

To prevent the flutes of the auger from ingesting soil before reaching the desired depth, the openings to the flutes would be covered by a drill cap during transport and impact. During the first 70° of rotation of the auger, the drill cap would not rotate; thus, the auger would rotate relative to the cap, bringing the openings to the flutes out from under the cap. Upon reaching 70°, the auger would engage the cap; thereafter the auger and cap would rotate together, so that the openings to the flutes would remain exposed.

This work was done by Tommaso P. Rivellini and Christopher J. Voorhees of Caltech for NASA's Jet Propulsion Laboratory. NPO-20163

NASA Tech Briefs Magazine

This article first appeared in the July, 1998 issue of NASA Tech Briefs Magazine.

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