Sampling cores requires the controlled breakoff of the core at a known location with respect to the drill end. An additional problem is designing a mechanism that can be implemented at a small scale that is robust and versatile enough to be used for a variety of core samples. This design consists of a set of tubes (a drill tube and an inner tube) and a rolling element (rolling tooth). An additional tube can be used as a sample tube. The drill tube and the inner tube have longitudinal holes with the axes offset from the axis of each tube. The two eccentricities are equal. The inner tube fits inside the drill tube, and the sample tube fits inside the inner tube.

The Rolling-Tooth Design of the core breakoff and retention mechanism (left), and the assembled parts (right).
While drilling, the two tubes are positioned relative to each other such that the sample tube is aligned with the drill tube axis and core. The drill tube includes teeth and flutes for cuttings removal. The inner tube includes, at the base, the rolling element implemented as a wheel on a shaft in an eccentric slot. An additional slot in the inner tube and a pin in the drill tube limit the relative motion of the two tubes. While drilling, the drill assembly rotates relative to the core and forces the rolling tooth to stay hidden in the slot along the inner tube wall. When the drilling depth has been reached, the drill bit assembly is rotated in the opposite direction, and the rolling tooth is engaged and penetrates into the core. Depending on the strength of the created core, the rolling tooth can score, lock the inner tube relative to the core, start the eccentric motion of the inner tube, and break the core. The tooth and the relative position of the two tubes can act as a core catcher or core-retention mechanism as well. The design was made to fit the core and hole parameters produced by an existing bit; the parts were fabricated and a series of demonstration tests were performed.

This invention is potentially applicable to sample return and in situ missions to planets such as Mars and Venus, to moons such as Titan and Europa, and to comets. It is also applicable to terrestrial applications like forensic sampling and geological sampling in the field.

This work was done by Mircea Badescu, Donald B. Bickler, Stewart Sherrit, Yoseph Bar-Cohen, Xiaoqi Bao, and Nicolas H. Hudson of Caltech for NASA’s Jet Propulsion Laboratory. NPO-47354

Topics:
Assembling Cutting Design processes Drilling Electrical systems Machining processes Manufacturing processes Mechanical Components Mechanics Parts Starters and starting Wheels
This Brief includes a Technical Support Package (TSP).
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Rolling-Tooth Core Breakoff and Retention Mechanism

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NASA Tech Briefs Magazine

This article first appeared in the June, 2011 issue of NASA Tech Briefs Magazine (Vol. 35 No. 6).

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Overview

The document presents a technical disclosure of NASA's Rolling-Tooth Core Break-Off and Retention Mechanism, identified as NPO-47354. This innovative mechanism addresses the challenge of sampling cores by enabling the controlled break-off of core samples at predetermined locations relative to the drill bit. The design is particularly relevant for space exploration missions, including potential sample return missions to Mars and other celestial bodies.

The core break-off mechanism consists of a set of eccentric tubes—a drill tube, an inner tube, and an optional sample tube—along with a rolling element known as a rolling tooth. The inner tube fits inside the drill tube, and both tubes have longitudinal holes that are offset from their axes, allowing for precise control during the drilling process. The rolling element is passively controlled by rotating the outer tube in the opposite direction of the normal drilling rotation, which engages the core and facilitates its break-off.

Key features of the mechanism include its ability to act as both a core breaking and retention device, utilizing the same actuator for both functions. The rolling tooth can score the core, lock it to the inner tube, and assist in breaking it off through torsion or shear forces. This dual functionality is a significant advancement over previous technologies, as it combines core sampling and retention in a compact and efficient design.

The disclosed mechanism is particularly applicable to NASA's exploration missions, supporting the goals of in-situ analysis and sample caching for future return to Earth. It is designed to fit within the dimensions of existing coring bits, making it suitable for various planetary missions, including those targeting Mars, Venus, and moons like Titan and Europa. Additionally, the technology has potential terrestrial applications in fields such as forensic sampling and geological exploration.

Overall, this document highlights a critical advancement in core sampling technology, addressing both the technical challenges of space exploration and the need for efficient sample acquisition methods. The mechanism's innovative design and functionality position it as a valuable asset for future NASA missions and other scientific endeavors.