Introduction

Drilling is a process of penetrating solid objects by creating holes using various tools or approaches. When applying rotation to create a hole, the bit has a circular cross section and the produced borehole has a round shape. Alternatively, percussive or hammering drills can create non-round boreholes. Mechanisms of penetrating objects and formations, i.e., drills, are widely used for many applications including making holes, sampling, exploration, and excavation (Bar-Cohen and Zacny, 2009; Clark, 1987; Hossain and Al-Majed, 2015; Rollins, 2010; Zacny et al., 2008). While the field is quite well established, there are still many challenges including operation at extreme conditions as well as drilling extremely hard materials. Drilling on other extraterrestrial bodies also poses significant challenges resulting from the limited resources that are available and the difficult conditions involved. The earliest successful planetary drilling was performed on the moon in 1970 by the Soviets’ robotic Luna 16 lander (Bar Cohen and Zacny, 2009). In recent years, missions have been increasingly launched to drill on Mars and penetrate the surfaces of other extraterrestrial bodies. 2These exploration missions are seeking to investigate the history of our solar system and better understand our planet Earth (Bar-Cohen and Zacny, 2009; Zacny et al., 2008, 2013a). To penetrate a large variety of materials on Earth, scientists and engineers have developed many types of drills, of which mechanical drills are the most common. These drills employ a bit with a tip that interacts with the drilled material and employs large shear and/or impact stresses over a small area to cut or break the formation. Such bits are widely used and are available commercially at local hardware stores.