SLUSH: Thermo-Mechanical Deep Drilling System for Ocean Worlds and Mars

SLUSH: Thermo-Mechanical Deep Drilling System for Ocean Worlds and Mars PI: Kris Zacny, Honeybee Robotics Ocean Worlds and Mars are of particular interest to Astrobiology since they could offer clues in the quest to discover life beyond our home planet. Europa has been a primary target in the search for past or present life because it is still geologically active and has a large ocean underneath an ice shell (despite being smaller than our Moon, Europa has more water than Earth). Therefore, we will focus technology development on Europa. However the proposed technology (with various degree of modification) could also be used on other Ocean Worlds and Mars. To advance forward, a probe would need to destroy the formation and move the drilled material behind it. This can be achieved via two primary methods: thermal and mechanical. Each of these two methods has unique advantages and disadvantages but neither is sufficient to reach the ocean. Thermal probes (e.g. melt probes, closed cycle hot water drills - CCHWD, lasers) are very robust penetrators that require just heat to melt through and advance deeper below the surface. Thermal probes, however, are slow (especially in cryogenic ice), require significant amount of power (kW to 10s of kW, depending on the probe's diameter and length), and are inefficient, because >90% of the heat is lost into surrounding ice. Mechanical drilling systems, on the other hand, are approximately 100x more efficient and significantly faster. For that reason they are primary methods of making holes and capturing ice cores in Greenland and Antarctica. They can also penetrate materials other than ice (e.g. salts). The major drawback of these drills relates to chips removal. Chips need to be removed by either periodically lifting the drill with chips basket out of the hole (conventional method used in terrestrial ice drilling) or lifting the chips above the probe and re-compacting them to their original density (e.g. inch worm approach). In summary, mechanical systems have very efficient formation breaking approach while thermal systems have very effective chips removal approach. SLUSH is a thermo-mechanical probe that combines the best from these two techniques: mechanical drill to break the formation and melting to remove the cuttings). However, instead of melting an entire volume of ice, SLUSH melts just a fraction of it to form slush. Slush behaves like liquid but is still partially frozen this enables significant reduction in power draw. Since mechanical approach generates higher penetration rates, SLUSH can also reach the ocean in much shorter time. SLUSH looks like a torpedo with a drill bit in front and anti-torque blades on the side (proven system in Antarctic wireline drills). It houses scientific instruments for in-situ analysis. It is connected to a surface lander by an umbilical for data and power. To reduce power draw from the surface energy supply needed for partial melting, SLUSH incorporates General Purpose Heat Source bricks with ~250 Watt thermal power. Once SLUSH passes through the cryogenic lice (a few km thick), it can use just a thermal approach to melt through the warmer ice without the need for mechanical cutting. Thermal probes are significantly more efficient in tempered (warm) ice. Under PICASSO, the TRL of SLUSH will be increased from TRL2 to TRL4. We would focus on two of the most critical technical aspects: drilling/melting and chips transport. To reach TRL4, we propose to: 1. Develop high level designs and thermal models for cryogenic and warm ice to establish power levels needed for partial melting, and constrain probe's diameter and length. 2. Breadboard critical subsystems that will support TRL4 SLUSH design. 3. Design and build TRL 4 SLUSH and test it in our 5 m tall freezer and in our 3.5 m tall thermal vacuum chamber in Europa analog ice. 4. Update high level SLUSH design based on test data. More »