Lunar Drilling – Challenges and Opportunities

Plans are being developed to drill and core a 100m deep hole on the Moon, an ambitious step beyond the 2.986m depth achieved at the Apollo 17 landing site in 1972. There are many scientific reasons for doing this, including determining the lunar geology and mineralogy below the meteorite-shattered regolith surface and its volatile content and heat flow, and identifying resources for future human space exploration. The complexities are such that the mission lead time is 15 plus years. Drilling in the lunar environment poses many different technical challenges compared with terrestrial activity, although there are parallels, starting with the geological prognosis, similar to an oilfield exploration play. Operationally, the drilling equipment must escape Earth's gravitational pull. It must then travel almost 400,000 km to the drill site before it can be deployed and drilling starts. With each Kilogram of payload currently costing over $1.2 Million (Astrobotic Payload User Guide) this limits the available continuous power to approximately 100W, a minute fraction of its terrestrial counterparts. At these distances a radio signal takes 2.5 seconds to make the round trip, so the deployment and subsequent drilling activities must be largely autonomous. To add to the difficulties, the Moon's gravitational pull is only one sixth that of the Earth and it has no atmosphere, introducing weight on bit and hole cleaning problems. Despite the low gravity, displaced solids can still fall and obstruct the hole and some form of casing will be needed to secure the hole as it is drilled. The associated weight, power and geometrical limitations make this another serious technical challenge that must be overcome. With little or no chance to intervene, the operation must aim to be engineered to be right-first-time. In the last decade, automation in oil and gas drilling has advanced considerably (Veila 2016; Hseih 2017). The number of autonomous activities has expanded and system reliability has improved. This, and other aspects of oil and gas experience, coupled with space exploration expertise and technology will be combined to make this happen. The pay-back for the oil and gas industry's involvement in this endeavor will be a step change in reliability and efficiency that results from satisfying the demanding conditions and clinical attention to detail that will be necessary to succeed. The paper contains details of the goals, challenges and current thinking that drilling on the Moon entails, and the parallels with oil and gas drilling. This comes at a time when there is a renewed interest in further exploration of our solar system, particularly the Moon and Mars.