Diver Propulsion Vehicle (DPV) Concept and Housing Design

The Papahānaumokuākea Marine Debris Project (PMDP) is a non-profit organization aiming to protect the wildlife in the Papahānaumokuākea Marine National Monument (PMNM) from marine debris. One of their key efforts is to remove derelict fishing nets from the reefs, which is a physically intensive, manual process that requires personnel to scout, dive, and cut nets caught on the reefs. To alleviate some of these divers’ physical toll, PMDP has explored existing Diver Propulsion Vehicles (DPVs) in the market, but many solutions do not have enough battery capacity for intermittent usage throughout the day. Hence, our team was tasked to develop a DPV that performs to the specifications of the PMDP divers. Notably, the DPV must be able to propel a diver at 0.75 m/s along the ocean surface and last at least an hour. We initially created a proof of concept to test the electronic setup, which would run the Blue Robotics T200 thruster that we selected based on the speed and calculated drag requirements. Through testing, we determined that the chosen thruster did meet the speed specifications, albeit only lasting for 15 minutes with the chosen battery. On top of this, it also revealed that the battery’s temperature exceeded its rated operating range, which can potentially be a safety hazard for the divers. To solve this, we selected a battery with greater capacity and integrated a thermal management system. This upgraded prototype successfully met speed requirement operating for more than an hour, all whilst the temperature of the battery was kept within its safe operating range. For the housing, we used Schedule 40 PVC plastic, which is durable and readily available. We also incorporated a momentary switch into the handles so the DPV would stop when the diver loses contact with it. Testing the housing revealed it was fully waterproof. In the end, we were able to develop two separate prototypes, each satisfying its own set of specifications we were aiming to have in our DPV. For future work, we would like to integrate these two systems and test its performance. Furthermore, we also believe that there can be further improvements made on the battery’s accessibility and power efficiency. Finally, we would like to provide the integrated prototype to PMDP divers for comprehensive feedback on its comfort and usability.