David Firstbrook

An experimental study of ultrasonic vibration and the penetration of granular material

This work investigates the potential use of direct ultrasonic vibration as an aid to penetration of granular material. Compared with non-ultrasonic penetration, required forces have been observed to reduce by an order of magnitude. Similarly, total consumed power can be reduced by up to 27%, depending on the substrate and ultrasonic amplitude used. Tests were also carried out in high-gravity conditions, displaying a trend that suggests these benefits could be leveraged in lower gravity regimes.

Power Optimisation for an Ultrasonic Penetrator in Granular Materials

The work undertaken in the paper investigates the power-saving capability of using direct ultrasonic vibration to facilitate sub-surface penetration through granular material. The results show that total power consumption of penetration can be reduced by 28%, with the greatest improvements occurring in higher density sands.

A novel study on high-powered ultrasonic penetrators in granular material

This work investigates the effects of high-powered ultrasonics in granular material. The aim is to facilitate penetration in granular material in low mass/low gravity environments. The results show that the weight on bit requirement for penetration is significantly reduced on application of direct ultrasonic vibration, especially in high relative density substrates.

Ultrasonically-Assisted Penetration of Granular and Cemented Materials

Granular material can often be penetrated by the application of high-frequency vibrations. This effect may be seen in loosely packed granular material, in permafrost where the discrete grains exist in an icy matrix, and even where those grains have been compacted and cemented to form a sedimentary rock. For space applications, the vibrations may be reasonably generated by a Langevin transducer and their energy delivered to the target material by a number of different mechanisms, depending on the nature of the target and the depth or bore diameter of the desired drill campaign. The application of such vibrations is generally associated with reductions in weight-on-bit and power requirements when compared to more traditional techniques.

Granular Materials in Space Exploration

This paper describes the effects of ultrasonically-assisted penetration of granular materials, in high gravity situations. The experimental rig, instrumented to obtain penetration force, rate and power both with and without ultrasonic assistance, was used to drive a penetrator into a granular material inside the ESA Large Diameter Centrifuge at accelerations of up to 10 g during early September 2015. Ultrasonic penetration proved to be most beneficial at lower levels of accelerations, reducing the required overhead weight by 80%, and the total power consumption by 27%.