A Space Age Drill: DIGGER- Drilling and Integrated GigaHertz-Generated Energy Resource for Lunar and Asteroid Applications

A Space Age Drill: DIGGERDrilling and Integrated GigaHertz-Generated Energy Resource for Lunar and Asteroid Applications. R.A. Bamford¹*, T. Wong², R. Macpherson², I. Timoshkin², S. MacGregor², L. Zhang³, D. Spiers³, C. Whyte³, A. MacLachlan³, K. Ronald³, B. Bingham¹ ³, I. Konoplev⁴, M. Martin⁵, S. Eves⁶, ¹ STFC RAL Space, Rutherford Appleton Laboratory, Harwell Campus, Didcot, Oxfordshire, OX11 0QX, U.K. ² Dept of Electronic and Electrical Engineering, Uni of Strathclyde, Royal College Building, 204 George Street, Glasgow G1 1XW, U.K. ³ Dept of Physics, Uni of Strathclyde, John Anderson Building, 107 Rottenrow, Glasgow, Lanarkshire, G4 0NG, U.K. ⁴ Culham Centre for Fusion Energy (CCFE), Culham Science Centre, Abingdon, OX14 3EB, U.K. ⁵ VULCAN Analogue Sample Facility at European Centre for Space Applications and Telecommunications (ECSAT), European Space Agency (ESA), Fermi Ave, Harwell, Didcot, OX11 0FD, U.K. ⁶ SJE Space Ltd., Reading, Berkshire, U.K. ([email protected]) Introduction: Accessing the subsurface of the Moon and small bodies is essential for scientific investigation, infrastructure deployment, and In Situ Resource Utilisation (ISRU), including the extraction of water ice, volatiles, and minerals critical for sustainable exploration and habitation. Current methods rely heavily on mechanical screw and hammer techniques—surely, a more advanced, space-age solution is overdue. The UKSA Funded NSIP project DIGGER (Drilling and Integrated GigaHertz-Generated Energy Resource) initiative explores two complementary and innovative approaches to nonmechanical subsurface access in lunar and asteroid environments. Both approaches aim to overcome the limitations of conventional drilling in vacuum and low-gravity conditions, where abrasive dust, mechanical wear, and thermal management pose significant engineering challenges. Pulsed Plasma Discharge in Porous Rock[1]: A COMSOL-based model was developed to simulate the mechanical response of porous rock under highenergy plasma discharges in vacuum conditions. The simulations consider a plasma channel formed within the rock matrix, delivering impulsive energy over microsecond timescales. Results show that within 25~µs, peak stresses reach 80~GPa, inducing elastic deformations up to 0.15~mm. These extreme stress conditions imply significant fracturing and localized material failure, suggesting that pulsed plasma discharge can effectively fragment rock for scientific sampling or resource extraction. This modelling provides critical insights into the mechanical behaviour of regolith and rock under fast, highintensity loads. Figure 1 shows holes drilled in sandstone using a 50 mm drill with a 7 mm inter-electrode gap, at applied voltages of 35 kV and 40 kV, delivering energy per pulse of 80 J (40 kV, one capacitor), 122.5 J (35 kV, two capacitors), and 160 J (40 kV, two capacitors). Figure 2 presents holes produced in granite (60 mm diameter) using a pulsed power supply operating at 60 kV and a discharge frequency of 2 Hz. Figure 1. A 50mm hole in sandstone created by a Plasma Drill . From [1]. Figure 2. Holes drilled in Granite by plasma drill. From [2] Microwave Drilling[2]: Drawing from established microwave heating principles, this method utilises dielectric loss to generate heat within target materials, eventually causing melting and vaporisation to form a borehole. The absence of mechanical parts within the wellbore offers significant advantages in terms of reliability and reconfiguration. A linearised thermal model was employed to evaluate energy efficiency and drilling speed across a range of microwave delivery systems, including coaxial, rectangular, and corrugated waveguides. Results indicate that higher frequency sources (tens to hundreds of GHz) substantially improve drilling rates compared to traditional mechanical drills. However, scaling microwave sources presents a challenge: available power decreases with increasing frequency . Gyrotrons emerge as viable sources at >50~GHz, albeit with size and weight penalties. Optimisation studies targeting the gyrotron's magnetic system indicate up to 30% mass reduction through careful shaping of the magnetic field profile and implementation of permanent magnet architectures. Figure 3 illustrates a microwave-drilled hole in low-purity alumina, adapted from Jerby (2004). A 6 mm diameter and 13 mm depth were achieved after 2 minutes of 0.9 kW microwave illumination. Figure 3. An example of a microwave-drilled hole in low-purity alumina. From [3] It should be noted that all the example holes presented here were produced under terrestrial conditions, not in vacuum or space environments, and involved the use of conductive media such as water, oil, or gases to facilitate discharge or heat transfer. One of the central challenges for the DIGGER project lies in adapting these still developing, innovative, high-energy terrestrial drilling techniques to the harsh and constrained conditions of space. Factors such as vacuum, extreme temperature variation, limited power availability, mass and volume restrictions, and the need for autonomous operation demand significant redesign and optimisation. Translating pulsed plasma discharge and microwave drilling systems into robust, spacequalified technologies requires careful consideration of materials, thermal management, energy delivery, and integration with robotic platforms, all while maintaining efficiency and reliability in lunar and asteroid environments. Conclusion: Together, these approaches, microwave and high voltage, offer a modular, scalable, and energy-efficient strategy for deep subsurface access in extra-terrestrial environments. Ongoing research focuses on integration pathways for lunar technology demonstration missions and the development of testbeds to evaluate these methods under simulated surface conditions. References [1] Timoshkin, I V. el al. IEEE Trans. on Plas. Sci. 32,. 5 (2004): 2055-2061 [2] Liu, W., et al., Geom and Geophys for Geo-Energy and Geo-Res, 9, 1 (2023): 22. [3] Jerby, O. et al., JAppl. Phys., 97,3, 2005