Rotary-Percussive Deep Drill for Planetary Applications

Terrestrial drills are normally deployed from massive platforms such as large trucks or stationary rigs. The drilling platform provides a reaction force for the drill, the so called Weight on Bit (WOB). Harder rocks require higher WOB to fracture, while softer rocks require lower WOB to fracture. In the case of planetary drilling, rovers and landers carrying drills have very low mass in comparison. Thus, maximum WOB that can be practically applied to a drill is highly limited for space applications. One solution to drilling with a low reaction force is to augment a rotary drill with a percussive hammer. The rotary-percussive drill requires a much lower Weight on Bit (WOB), than a pure rotary drill and it can also penetrate very hard rocks more efficiently. That is, with less overall energy. However, the downside of a rotary-percussive system is added power and complexity compared to a pure rotary system. In this paper, custom designed and Commercial, off-the-shelf (COTS) rotary-percussive drill systems are described and preliminary drilling results in various formations, including ice, limestone, and hard basalts are presented.