Preliminary Evaluation on the Operational Use of Magnetic Connections in the Deployment of a Rapid-Deployment Amphibious Robotic Chassis

Project CIPACTLI (Compact Integrated Polymer Amphibian for Coastal and Littoral Investigation) evaluates the operational limits of rare-earth magnetic connections in a cannon-inserted amphibious robotic chassis designed for search-and-rescue (SAR) and environmental monitoring. Two prototype iterations were systematically compared across movement speed, structural loading, and ballistic survivability under combustion-cannon deployment. The first prototype employed a tensegrity-inspired, serpentine soft robot with segmented inflatable buoyancy modules connected via magnetic couplings. A 2³ factorial design evaluated three factors: core tendon material (nylon versus steel), terrain (terrestrial versus aquatic), and magnet type (flexible magnetic tape versus rare-earth neodymium N52 magnets). Results showed no significant effect of magnet type on movement speed (p = 0.507), with tendon material dominating performance (partial η² = 0.637). Both magnet types achieved 100% survival under impulsive cannon launch, indicating that chassis compliance attenuates peak shock below the brittle-fracture threshold of neodymium magnets. The second prototype eliminated magnetic couplings and inflatable actuators in favor of a monolithic PLA body with integrated buoyancy. This design demonstrated a 6.96-fold increase in compressive load capacity (p = 0.001) and equivalent ballistic survivability, though with a 24.9% reduction in aquatic movement speed. Tethered deployment trials validated mechanical viability for maritime SAR applications. These findings demonstrate that rare-earth neodymium magnets confer no performance advantage over flexible magnetic tape within the tested operational envelope, and that structural integration—not magnet grade—governs resilience under impulsive loading. The results counsel against blanket substitution of rare-earth magnets into impact robotics without task-specific justification, supporting expanded evaluation of polymer-bonded composites and ferrite-bonded tapes as lower-criticality alternatives.