Ultrasonic Drilling and Coring for Planetary Astrobiological Applications

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Planetary exploration is the key to one of the most exciting scientific endeavours of the 21st century; the search for life outside planet Earth. A primary role for surface rovers in planetary exploration is exobiological prospecting. Autonomous rovers are the key to finding evidence of former or extant prebiotic or biotic species. For this purpose, reliable and effective instruments that can sample and conduct in-situ astrobiology analysis need to be developed. Currently, drilling requires large axial forces and holding toques and high power. This limits conventional driller/corer applications to very stable and large platforms with solid anchoring. Conventional drillers consume a lot of energy, are subject to drill bit jamming, breaking and dulling, are difficult to use for non-vertical operations and the drilling process is hampered by the accumulation of drilling debris. The aim of this study is therefore to model, design, build and test an ultrasonic driller/corer for planetary astrobiological applications The fundamental principle of ultrasonic drilling is to oscillate a cutting tool in the low ultrasonic frequency range, to produce a small axial motion at a relatively high velocity. The impact of the tool against the surface of the rock produces micro-fractures in the crystal and mineral structure causing the surface to be eroded and broken, thus allowing drilling or cutting to be achieved using a modest preload. The proposed research will develop a novel approach to ultrasonic drilling/coring by adapting flextensional ultrasonic transducers as the driving end of the device, allowing the drill to be miniaturised without loss of vibration amplitude, and to remove the need for rotational drilling. The design will rely on the development of validated finite element models of ultrasonic drilling in rock, in order both to compare different drill designs and to predict the vibration and temperature responses of the drill and workpiece. Bringing essential expertise and support to this project, the industrial partner, EADS Astrium, has world-renowned expertise in the highly specialised field of space science, with several space industry firsts to its credit. EADS Astrium owns some of the best-appointed and most advanced design, manufacture and test facilities in the space industry. The challenges in designing a small, low power, low preload ultrasonic driller/corer to cut through rock, equally apply to the design of novel ultrasonic devices for welding processes and food cutting applications. Currently, ultrasonic welders are large assemblies but, with the move towards miniaturisation of electronic and medical devices, the capability of joining dissimilar materials such as metals, ceramics and glass, has become of paramount importance. Ultrasonic cutting of food products has proved to be an effective technology, achieving substantial reductions in product waste and improved cut quality at increased cutting speed. However, ultrasonic cutters tend to be large tools capable of cutting only a limited range of food products. For both applications, successful design of the ultrasonic driller/corer will provide opportunities for the design of a new generation of low power ultrasonic welding devices and cutters, adaptable to a much wider variety of materials. The UK division of Branson Ultrasonics, the second industrial partner, is the market leader in ultrasonic welding and, as a result of close relationships with the food industry, has recently developed several new innovations for ultrasonic cutting of food products. Branson are therefore in a unique position in the UK to collaborate in this research project.