Drills as Tools for Media Penetration and Sampling

Drilling and excavation are widely applied for many purposes, including making a hole in a wall, deep drilling in the search for oil and exploration of the Earth’s subsurface (Clark, 1987). Most of what we have learned about early climates of planet Earth (e.g., ice ages) was obtained from cores taken by drilling through ice sheets and glaciers (e.g., Dansgaard, 2004). Increasingly, developers of drills are addressing complex challenges in extreme environments, for example penetrating the surface of planetary bodies. Drilling on the Moon is an example of such a challenge, which was successfully accomplished for the first time in 1970 by the Soviet’s robotic Luna 16 lander. This success was followed with the growing efforts to drill on Mars and penetrating the surfaces of other extraterrestrial bodies and increasingly enabling scientists to investigate the history of our Solar System and understand better our own planet Earth (Zacny et al., 2008). To address the challenges presented by the large variety of materials that need to be penetrated in drilling into our own planet’s surface, scientists and engineers have developed many types of drills, with mechanical drills being the most common. Mechanical drills use a bit with a tip that interacts with the drilled medium and applies cutting or breaking forces over a small area to achieve large shear and/or impact stresses. These types of bits are widely used and can be purchased at local hardware stores. Penetrating solid objects, such as the ground, rocks and wood, has been achieved by creatures and plants in Nature ever since they first existed on Earth millions of years ago. The earthworm, termites (Figure 1.1), rodents, the woodpecker (Figure 1.2) and many others are capable of making holes and tunnels for their habitat and search for food (Bar-Cohen, 2005). Also, roots of plants have amazing capabilities to penetrate rocks and hard soil. Since ancient times, humans have been digging through the ground and solid objects. There are many reasons to dig and, over the years, as more effective tools became available, the capability to penetrate various media increased. Some of the