This novel core break-off and retention mechanism consists of a scoring dawg controlled by a set of two tubes (a drill tube and an inner tube). The drill tube and the inner tube have longitudinal concentric holes. The solution can be implemented in an eccentric tube configuration as well where the tubes have eccentric longitudinal holes. The inner tube presents at the bottom two control surfaces for controlling the orientation of the scoring dawg. The drill tube presents a sunk-in profile on the inside of the wall for housing the scoring dawg. The inner tube rotation relative to the drill tube actively controls the orientation of the scoring dawg and hence its penetration and retrieval from the core. The scoring dawg presents a shaft, two axially spaced arms, and a tooth. The two arms slide on the control surfaces of the inner tube. The tooth, when rotated, can penetrate or be extracted from the core.
During drilling, the two tubes move together maintaining the scoring dawg completely outside the core. After the desired drilling depth has been reached the inner tube is rotated relative to the drill tube such that the tooth of the scoring dawg moves toward the central axis. By rotating the drill tube, the scoring dawg can score the core and so reduce its cross sectional area. The scoring dawg can also act as a stress concentrator for breaking the core in torsion or tension. After breaking the core, the scoring dawg can act as a core retention mechanism.
For scoring, it requires the core to be attached to the rock. If the core is broken, the dawg can be used as a retention mechanism. The scoring dawg requires a hard-tip insert like tungsten carbide for scoring hard rocks. The relative rotation of the two tubes can be controlled manually or by an additional actuator. In the implemented design solution the bit rotation for scoring was in the same direction as the drilling. The device was tested for limestone cores and basalt cores. The torque required for breaking the 10-mm diameter limestone cores was 5 to 5.8 lb-in. (0.56 to 0.66 N-m).
This work was done by Mircea Badescu, Stewart Sherrit, Yoseph Bar-Cohen, Xiaoqi Bao, and Paul G. Backes of Caltech for NASA’s Jet Propulsion Laboratory. NPO-47355
This Brief includes a Technical Support Package (TSP).
Scoring Dawg Core Break-Off and Retention Mechanism
(reference NPO-47355) is currently available for download from the TSP library.
Don't have an account?
Overview
The document presents the Scoring Dawg Core Break-Off and Retention Mechanism, a novel technology developed by NASA's Jet Propulsion Laboratory (JPL) for efficient core sampling in various environments, including extraterrestrial missions like Mars Sample Return (MSR). The mechanism is designed to facilitate the controlled break-off of drill cores at a predetermined location, which is crucial for accurate sampling.
The core mechanism consists of a set of concentric or eccentric tubes, with an inner tube that may include a sample tube for retaining the collected core. The design incorporates a scoring element, referred to as the "scoring dawg," which is actively controlled by rotating the inner tube relative to the outer tube. This rotation allows for precise scoring of the core, assisting in both the break-off process and the retention of the core sample.
The document outlines the technical challenges addressed by this invention, particularly the need for a robust and versatile mechanism that can operate effectively at a small scale. The scoring dawg features a shaft, two axially spaced arms, and a tooth that can penetrate or be extracted from the core, depending on the orientation controlled by the inner tube's rotation. This innovative design not only enhances the efficiency of core sampling but also ensures that the integrity of the sample is maintained during the process.
Testing of the mechanism involved breaking limestone and basalt cores, with torque measurements for limestone indicating a range of 5 to 5.8 in-lb (0.6 to 0.65 N-m). While the torque for basalt was not measured, the results demonstrate the mechanism's effectiveness in handling different types of geological materials.
The document emphasizes the broader applications of this technology beyond space exploration, including forensic and geological sampling on Earth. It highlights the potential for this mechanism to revolutionize core sampling techniques in various fields, making it a significant advancement in drilling technology.
Overall, the Scoring Dawg Core Break-Off and Retention Mechanism represents a critical step forward in the ability to collect and preserve geological samples, with implications for both scientific research and practical applications in diverse environments.
