Our blue tailcone may be the most recognizable feature on our AUVs, and it represents a long history of experimentation and development of underwater propulsion systems. From the multi-thruster HAUV to the buoyancy-driven Spray Glider to the ducted tailcones on the torpedo-style AUVs, we have put thousands of hours into making many different shapes and sizes of vehicles move efficiently through the water.

The tailcone—our most versatile propulsor—is the result of a joint research effort between MIT and MBARI that culminated in field demonstrations on Bluefin BPAUVs in 2000. In designing this tailcone we wanted to eliminate the protruding dive planes and control fins common to many AUVs. The sleek design reduces the likelihood of damage and biofouling while simplifying the entire assembly down to a single easily replaceable module. The resulting ducted thruster design is also more hydrodynamically advantageous than the commonly used fin design.The tailcone is an articulating, ducted thruster that provides exceptional propulsive efficiency, dynamic stability, and control in a compact, robust structure. It is also designed to be torque-neutral, so the vehicle roll is not significantly affected by the propeller speed. Electronics integrated directly into the tailcone module control the propeller speed as well as rudder and elevator angles. The thruster enables vehicles to operate from 0.5 knots up to 5 knots through the water and can provide dynamic control performance sufficient to accommodate nearly any integrated payload.

Though the original tailcone was built for the BPAUV, a configuration of the Bluefin-21 vehicle, the tailcone design has been adapted for the Bluefin-9 and Bluefin-12 vehicles as well. All three vehicles use a common baseline control module with a duct and propeller specific to vehicle size. The tailcones themselves are a standalone oil-compensated subsystem, connected to the main electronics housing by a single wet cable, and as a result can be quickly changed out in the field.

Ongoing research is continuously improving the Bluefin tailcone design and exploring new propulsion technologies that leverage our fundamental design elements. Expect to see smaller and even more efficient systems in the years to come.