An ultrasonic rock-abrasion tool (URAT) was developed using the same principle of ultrasonic/sonic actuation as that of the tools described in two prior NASA Tech Briefs articles: “Ultrasonic/Sonic Drill/Corers With Integrated Sensors (NPO-20856), Vol. 25, No. 1 (January 2001), page 38 and “Ultrasonic/Sonic Mechanisms for Drilling and Coring” (NPO-30291), Vol. 27, No. 9 (September 2003), page 65. Hence, like those tools, the URAT offers the same advantages of low power demand, mechanical simplicity, compactness, and ability to function with very small axial loading (very small contact force between tool and rock).
Like a tool described in the second of the cited previous articles, a URAT includes (1) a drive mechanism that comprises a piezoelectric ultrasonic actuator, an amplification horn, and a mass that is free to move axially over a limited range and (2) an abrasion tool bit. A URAT tool bit is a disk that has been machined or otherwise formed to have a large number of teeth and an overall shape chosen to impart the desired shape (which could be flat or curved) to the rock surface to be abraded. In operation, the disk and thus the teeth are vibrated in contact with the rock surface. The concentrated stresses at the tips of the impinging teeth repeatedly induce microfractures and thereby abrade the rock. The motion of the tool induces an ultrasonic transport effect that displaces the cuttings from the abraded area.
The figure shows a prototype URAT. A piezoelectric-stack/ horn actuator is housed in a cylindrical container. The movement of the actuator and bit with respect to the housing is aided by use of mechanical sliders. A set of springs accommodates the motion of the actuator and bit into or out of the housing through an axial range between 5 and 7 mm. The springs impose an approximately constant force of contact between the tool bit and the rock to be abraded. A dust shield surrounds the bit, serving as a barrier to reduce the migration of rock debris to sensitive instrumentation or mechanisms in the vicinity. A bushing at the tool-bit end of the housing reduces the flow of dust into the actuator and retains the bit when no axial load is applied.
This work was done by Benjamin Dolgin, Stewart Sherrit, Yoseph Bar-Cohen, Richard Rainen, Steve Askin, Donald Bickler, Donald Lewis, John Carson, Stephen Dawson, Xiaoqi Bao, and Zensheu Chang of Caltech and Thomas Peterson of Cybersonics for NASA’s Jet Propulsion Laboratory. For further information, access the Technical Support Package (TSP) free on-line at www.techbriefs.com/tsp under the Machinery/Automation category. NPO-30403
This Brief includes a Technical Support Package (TSP).
Ultrasonically Actuated Tools for Abrading Rock Surfaces
(reference NPO-30403) is currently available for download from the TSP library.
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Overview
The document presents an overview of the Ultrasonic Rock Abrasion Tool (URAT), a novel device developed for efficiently abrading rock surfaces, particularly in extraterrestrial environments. The URAT utilizes an ultrasonic/sonic drive mechanism that incorporates a piezoelectric actuator, an amplification horn, a free mass, and a specially designed abrasion bit. This innovative tool is capable of drilling through hard rock types, such as basalt, using low power (less than 5 watts) and minimal axial force, making it suitable for applications in space exploration.
The design of the URAT features a drill-head equipped with a multitude of teeth that impact the rock surface, inducing micro-fractures and facilitating the abrasion process. The document details the construction of the abrasion bit, which resembles a meat tenderizer with machined teeth that enhance the tool's effectiveness. The bit is attached to a shank that fits around the horn, with a free mass positioned inside the shank to optimize performance.
A shorter version of the URAT is also being developed, which employs a folded horn design. This version includes a cylindrical housing that contains the piezoelectric actuator, with mechanical sliders aiding its movement. The device is activated by applying force to the housing, allowing the actuator and bit to extend into the rock while maintaining constant contact through a set of springs. A dust shield is incorporated to minimize debris migration, protecting sensitive components.
The document highlights the successful testing of the URAT under simulated Martian conditions, demonstrating its potential for future planetary exploration missions. The control of the device is managed through a field programmable gate array (FPGA), which allows for precise operation and monitoring of the tool's performance.
Overall, the URAT represents a significant advancement in rock abrasion technology, combining innovative design with efficient operation to meet the challenges of drilling in harsh environments. The document serves as a technical support package, providing insights into the development and capabilities of the URAT, while also offering resources for further exploration of related technologies within NASA's research initiatives.
