This innovation comprises a compact drill that uses low-axial preload, via vibrations, that fractures the rock under the bit kerf, and rotates the bit to remove the powdered cuttings while augmenting the rock fracture via shear forces. The vibrations “fluidize” the powered cuttings inside the flutes around the bit, reducing the friction with the auger surface. These combined actions reduce the consumed power and the heating of the drilled medium, helping to preserve the pristine content of the produced samples.
The piezoelectric actuator impacts the surface and generates shear forces, fragmenting the drilled medium directly under the bit kerf by exceeding the tensile and/or shear strength of the struck surface. The percussive impact action of the actuator leads to penetration of the medium by producing a zone of finely crushed rock directly underneath the struck location. This fracturing process is highly enhanced by the shear forces from the rotation and twisting action. To remove the formed cuttings, the bit is constructed with an auger on its internal or external surface. One of the problems with pure hammering is that, as the teeth become embedded in the sample, the drilling efficiency drops unless the teeth are moved away from the specific footprint location. By rotating the teeth, they are moved to areas that were not fragmented, and thus the rock fracturing is enhanced via shear forces. The shear motion creates ripping or chiseling action to produce larger fragments to increase the drilling efficiency, and to reduce the required power.
The actuator of the drill consists of a piezoelectric stack that vibrates the horn. The stack is compressed by a bolt between the backing and the horn in order to prevent it from being subjected to tensile stress that will cause it to fail. The backing is intended to transfer the generated mechanical vibrations towards the horn. In order to cause rotation, the horn is configured asymmetrically with helical segments and, upon impacting the bit, it introduces longitudinal along the axis of the actuator and tangential force causing twisting action that rotates the bit. The longitudinal component of the vibrations of the stack introduces percussion impulses between the bit and the rock to fracture it when the ultimate strain is exceeded under the bit.
This work was done by Stewart Sherrit, Xiaoqi Bao, Mircea Badescu, and Yoseph Bar-Cohen of Caltech for NASA’s Jet Propulsion Laboratory.
In accordance with Public Law 96-517, the contractor has elected to retain title to this invention. Inquiries concerning rights for its commercial use should be addressed to:
Innovative Technology Assets Management JPL Mail Stop 202-233 4800 Oak Grove Drive
Pasadena, CA 91109-8099 E-mail: This email address is being protected from spambots. You need JavaScript enabled to view it.
Refer to NPO-47216, volume and number of this NASA Tech Briefs issue, and the page number.
This Brief includes a Technical Support Package (TSP).
Single Piezo-Actuator Rotary-Hammering Drill
(reference NPO-47216) is currently available for download from the TSP library.
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Overview
The document presents the Single Piezo-Actuator Rotary-Hammering Drill (SPaRH), developed by NASA's Jet Propulsion Laboratory (JPL) under the National Aeronautics and Space Administration (NASA) contract. This innovative drilling mechanism addresses the challenges faced by conventional drills used in subsurface sampling for astrobiology studies on other planets, such as Mars.
The SPaRH drill utilizes a single piezoelectric stack actuator to simultaneously generate both rotational and percussive hammering actions. This design significantly reduces the complexity and number of moving parts compared to traditional drilling mechanisms, which often rely on multiple actuators and gear systems. By minimizing the number of components, the SPaRH drill enhances reliability and reduces the risk of mechanical failure during missions.
The operational principle of the SPaRH drill involves the actuator generating impacts and shear forces that fracture the rock beneath the drill bit. The percussive action creates a zone of finely crushed material directly under the bit, while the rotational motion helps to remove the cuttings efficiently. This dual-action approach not only improves drilling efficiency but also preserves the integrity of the samples collected, as the produced cuttings are fine powders that are less likely to undergo crystallographic structure modification.
The document highlights the advantages of the SPaRH drill, including its ability to fluidize powdered cuttings, which reduces friction and power consumption during drilling. This feature is crucial for maintaining the pristine condition of samples, which is essential for accurate scientific analysis. The design also eliminates the need for lubrication, further reducing the risk of contamination.
In summary, the SPaRH drill represents a significant advancement in drilling technology for planetary exploration. Its innovative use of a single piezoelectric actuator for both rotation and hammering offers a more efficient, reliable, and contamination-free method for subsurface sampling. This technology is poised to enhance NASA's capabilities in the search for present or past life in the universe, making it a vital tool for future exploration missions.
