One of the fascinating features of this ship is its unconventional propulsion system. This system is comprised of two stern thrusters that rotate throughout 360º of rotation—while providing over 4000 Hp of thrust each.
In the bow, there are two more thrusters. One is a tunnel thruster, in a tube open from one side of the bow to the other. Just aft of it is a second thruster, a “swing down” thruster that can pivot down out of a second “tunnel” (open on the bottom) to provide thrust through 360º of rotation. This remarkable propulsion unit can also work in the up position, providing thrust to port or starboard. These two bow thrusters each are rated to provide up over 2200 Hp. All of the ship’s thrusters are driven by variable speed electric motors. The pitch of the ships propellers is fixed; the amount of thrust is controlled by the speed the propellers are rotated. This system allows precision control of the output of each thruster, a vital capability for the work this vessel does. Since this ship has electric motors coupled to the propellers, there are no traditional shafts. The Dependable has 5 Rolls-Royce Diesel Electric generating sets, each producing up to 1990 kW. The ship can run from one to all five generators, depending on the load. Electrical energy is from the engine/generator sets to the thruster on power cables, eliminating the power loss inherent in a traditional propeller shaft.
--Scott McMullen, Oregon Fishermen's Cable Committee, onboard the TE SubCom Dependable.