Autonomous and ultrasonically assisted drilling in a range of rocks and ice

Drilling in extreme environments may require reductions in weight-on-bit, applied torque, or energy use, without compromising rate-of-progress. This paper examines the use of ultrasonic vibration, directly superimposed onto an augering coring bit, to achieve this goal in aircrete, limestone, marble, tuff, and ice. Compared to traditional rotary drilling processes using the same tool, the ultrasonically assisted drilling processes demonstrated improved rate-of-progress (∼400%) in all materials studied. In aircrete and limestone, there were also modest but consistent reductions in torque power demand and, at optimum vibration amplitudes, total energy consumption (∼25%). The other materials gave more mixed results: ultrasonically assisted drill cycles in marble were energy intensive, those in tuff were unpredictable due to the inconsistencies in that material, and those in ice led to the failure of the tooth bonding.