| A goal of robotic surface missions to Mars is to carry out in-situ analysis of geologic samples and, eventually, return samples to Earth. While sample acquisition is presently limited to surface materials, there is growing interest in acquiring samples from deep below the surface. This will require an instrument such as a drill. There exists a large body of knowledge concerning drilling on Earth, particularly from the petroleum industry, but no work has been done on the mechanisms of drilling under Martian conditions. The purpose of this research was to investigate the drilling mechanics of coring drill systems under simulated Martian conditions. Drilling tests were conducted in a purpose built semi-autonomous drilling platform that included a Mars environmental chamber.;More than 25 meters were drilled into sandstones, basalt and soils with various water saturations, and in ice. Most tests were performed under simulated Martian conditions using custom built coring bits. To cope with a large variety of formations a hybrid bit was also designed and built. The main discovery included a sublimation effect when drilling ice bound formations at pressures at or below triple point of water. Sublimation increased drilling and cuttings removal efficiency and helped to maintain the bit and the formation temperature low. However, it also reduced the bit life. A blast of moderately compressed gas flowing from a one liter container was found to be an effective means of cuttings removal. Liquid water was also found drastically to increase the risk of contamination of samples with bacteria present on the surface of the drill. The effect of pressure and temperature on sliding friction was also studied. Additionally, drills were tested during a field trip in the Arctic. The performance of drill bits and the effectiveness of the cuttings removal system were found to be very different under Mars conditions. Mars drilling, therefore, is a field of study of its own.;For a more thorough summary of this research work, please refer to the 'Executive Summary' section. |
