Icy-Moon Cryo Environment Penetrating Ice Claw (ICE-PIC)

The goal of this research project was to design, prototype, and test an anchoring system for use on Europa. Since mobility or stability may be required for exploration and ice sample acquisition, a lightweight, low complexity, reusable, and reliable anchoring system was sought after. Maintaining the structural integrity of the ice while creating an anchor point and ensuring reliability despite minimal sensing were primary goals.
The initial objective was to develop a sublimation-based thermal pick to be used as both a thermal drill and anchor on Europa’s surface ices. Testing begun with cryogenic carbon dioxide ice at ambient pressure to determine the nature of sublimation thermal drilling. Prototype thermal picks that are thermally conductive anchors with embedded heaters were developed for this testing. The sublimation approach proved to be consistent, but in order to provide fast insertion speeds, the approach of storing thermal energy within the thermal pick itself was employed.
Testing was then transitioned into a thermal vacuum chamber to test thermal picks in water ice at cryogenic vacuum conditions (-170°C at 50mPa). Once these planetary testing conditions were reached, we identified new ice failure modes but also a significant opportunity in the possibility for melting. The thermal mass storage approach that we had employed in previous testing resulted in the unexpected observation of melting. Targeting melting rather than sublimation brings advantages in energy cost and rate of penetration, but the disadvantage comes in the introduction of new ice failure modes. Dramatic temperature differentials, heat transfer rates, and rapid phase transitions can lead to fracturing the water ice and significant degradation of its structure and load bearing capacity. However, approaches to mitigate these failure modes have been established.
The performance of the thermal pick has exceeded the initial expectations for the technology. Thermal efficiencies of ~50% relative to a melting regime have been demonstrated, which corresponds to approximately 200+% relative to a sublimation regime. This shows the significant energy savings that can be achieved by targeting melting. The additional energy costs of thermal pick warming and conduction at the thermal pick attachment point are highly design dependent but represent a significant portion of the energy costs of an anchoring process. Anchoring strengths of 130N have been reliably demonstrated at insertion depths as shallow as 6.5mm without ice failure.
The applicability of this technology will be highly dependent upon the ice conditions found on Europa and the type of exploration vehicle sent there but the desired characteristics of low complexity, low mass, reusability, and reliability have been demonstrated under the testing conditions used.