Development of an underwater glider equipped with an auxiliary propulsion module

A low power propeller based propulsion module has been developed to complement the buoyancy engine of a 200 m Slocum electric glider. This device is introduced to allow new behaviours such as horizontal flight and faster overall speeds to expand the existing operational envelope of underwater gliders. The design goal is to match typical horizontal glider speeds of 0.3 m/s while minimising the impact of the module on the performance of the unmodified glider. After careful selection of the propeller and motor candidates the stand-alone propulsion module has been tested in a small flume tank to verify the system's performance. Since the desired flight trajectory is restricted to the horizontal plane the validity of a previously published hydrodynamic model of the glider at zero angle of attack was verified by conducting drag measurements at various flow velocities at full scale in a larger flume tank. Self propulsion tests were also performed to establish the performance of the glider with the new propulsion module in a larger flume tank and in a towing tank. Open water tests were performed in a large test tank to show the stability of the platform for horizontal flight. The results from these tests show that the new propulsion module is capable of driving the vehicle horizontally while matching the performance of the conventional glider.