Humans have been digging underground for millennia – on Earth. It’s where we extract some of our most valuable resources that have moved society forward. For example, there wouldn’t have been a Bronze Age without tin and copper – both of which are primarily found underground. But when it comes to drilling on celestial bodies, we face unique challenges that make the process incredibly difficult. This is a significant issue that needs to be addressed if we ever hope to utilize the potential resources that lie beneath the surface of other planets and moons. A paper from Dariusz Knez and Mitra Kahlilidermani of the University of Krakow sheds light on why drilling in space is so challenging and explores potential solutions.

In their paper, the authors highlight two primary categories of difficulties when it comes to drilling off-world – environmental challenges and technological challenges. Let’s delve into the environmental challenges first.

One major obstacle when drilling on celestial bodies is the lack of an atmosphere. While some exceptions like Venus and Titan exist, most rocky bodies lack the atmosphere required to support fundamental drilling materials, such as fluids. On Earth, cooling fluids play a crucial role in drilling, preventing the drill bit or workpiece from overheating and deforming. However, in space, liquids exposed to the vacuum of space would immediately sublimate, providing little to no cooling effect. This poses a significant challenge for drilling operations, especially those conducted autonomously by rovers or landers.

Another issue is the limitations of hydraulic systems, commonly used in drilling rigs on Earth. Extreme temperature variations in space make it difficult to maintain a liquid in hydraulic systems, as they may freeze in cold conditions or evaporate in high temperatures. These challenges, coupled with other factors like abrasive regolith and the absence of a magnetic field for guidance, make drilling in space incredibly complex.

Technological challenges further complicate the drilling process off-world. Weight constraints are a critical consideration in space missions, and the heavy materials typically used in drilling rigs on Earth are not feasible for space exploration due to the high cost of launching such materials. Additionally, power sources for drilling systems in space must rely on solar cells and batteries, as traditional hydrocarbon-fueled engines are not viable off-Earth.

Despite these challenges, advancements in drilling technology are essential for the success of future space exploration endeavors, including crewed missions. To address these challenges, researchers are exploring innovative drill designs tailored for different depth categories, ranging from shallow-depth drills to large-depth drills. These designs incorporate concepts like inchworm systems and ultrasonics to enhance drilling capabilities in space.

While drilling off-world, particularly on asteroids and comets, remains a formidable task, it is essential for achieving ambitious goals like creating lunar cave cities or exploring ocean worlds like Enceladus. As we continue to refine drilling technologies and techniques, we move closer to unlocking the full potential of resources hidden beneath the surfaces of celestial bodies.

Image Caption: Curiosity’s arm with its drill extended. Credit – NASA/JPL/Ken Kremer/kenkremer.com/Marco Di Lorenzo