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

Here we discuss the design, development, and system engineering of the SWIM (Sensing With Independent Micro-swimmwers) system, which consists of decimeter-scale, swimming micro-robots (micro-swimmers) equipped with ocean composition sensors, propelled by miniature actuators, and wire-lessly communicating through water with ultrasound waves – envisioned to explore the ice-ocean interface of an Ocean World like Europa or Enceladus. The micro-swimmers are designed with a delta-wing form-factor for efficient packing of dozens of robots within a 5-10 liter cylindrical payload volume less than 30 cm in diameter, and intended to be deployed individually or as a swarm from a single cryobot mothercraft. SWIM robots are designed with primary redundancy through multiple robots (rather than subsystem redundancy found in many conventional NASA spacecraft), and simple but robust mechanisms able to survive 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 leverage a combination of miniature COTS components and custom-fabricated hardware. Uniquely, current SWIM prototypes are 369 x 152 x 65-130 mm and 1.7 L volume – approx. 3x larger dimensions and 22x larger volume than the intended final design (120 mm length and 75-100 mL volume) due to COTS hardware, but still sufficiently sized to descend through 6-inch boreholes drilled in ice on Earth to facilitate future field testing. Preliminary results of the integrated prototype robot, including in-water open-loop and closed-loop testing at up to 1.2 m/s (3.25 BL/s), as well as simulations of multiple swarm control strategies, will also be presented.