Double-acting pneumatic system for inducing motion in a floating vessel

An improved vessel for use in icecovered waters comprising a hull, a motion inducing tank disposed in the hull at a location spaced from the hull even-keel center of buoyancy, port means for communicating the lower extent of the tank to the exterior of the hull below the load waterline for flow of water into and out of the tank in response to pressure in the tank being different from ambient pressure outside the hull, the tank extending vertically in the hull from a lower end located below the hull load waterline to an upper end located above said waterline substantially as far as the location of said port means below said waterline, and air flow means coupled to the upper extent of the tank and operable alternately for generating superatmospheric and subatmospheric air pressure in the tank, the airflow means including an air pressurizing device having a suction connection and a discharge connection, duct means for coupling the suction connection separately to the upper extent of the tank and to atmosphere and for coupling the discharge connection separately to the upper extent of the tank and to atmosphere, and valve means in the duct means operable between

• a. a first state in which
• 1. the suction connection is coupled to the tank and
• 2. the discharge connection is coupled to atmosphere thereby to generate subatmospheric pressure in the tank, and
• b. a second state in which
• 1. the suction connection is coupled to atmosphere and
• 2. the discharge connection is coupled to the tank thereby to generate superatmospheric pressure in the tank.