Design and Development of SWIM – Miniature, Untethered Underwater Robots for Exploring Ice-Ocean Interfaces

Here we discuss the design, development, and systemengineering of the SWIM (Sensing With Independent Microswimmwers) system, which consists of decimeter-scale, swimming micro-robots (micro-swimmers) equipped with ocean composition sensors, propelled by miniature actuators, and wirelessly communicating through water with ultrasound waves –envisioned to explore the ice-ocean interface of an Ocean Worldlike Europa or Enceladus. The micro-swimmers are designedwith a delta-wing form-factor for efficient packing of dozens ofrobots within a 5-10 liter cylindrical payload volume less than30 cm in diameter, and intended to be deployed individually oras a swarm from a single cryobot mothercraft. SWIM robotsare designed with primary redundancy through multiple robots(rather than subsystem redundancy found in many conventionalNASA spacecraft), and simple but robust mechanisms able tosurvive a long flight / descent phase and high-pressure environment. Work to date has focused on design, fabrication, testing,and integration of 6 main subsystems – sensing, propulsion,steering, communication, power, and structure – that leveragea combination of miniature COTS components and customfabricated hardware. Uniquely, current SWIM prototypes are369 x 152 x 65-130 mm and 1.7 L volume – approx. 3xlarger dimensions and 22x larger volume than the intendedfinal design (120 mm length and 75-100 mL volume) due toCOTS hardware, but still sufficiently sized to descend through6-inch boreholes drilled in ice on Earth to facilitate future fieldtesting. Preliminary results of the integrated prototype robot,including in-water open-loop and closed-loop testing at up to 1.2m/s (3.25 BL/s), as well as simulations of multiple swarm controlstrategies, will also be presented.