Anti-rolling gyro

Ship stabilizing gyroscopes are a technology developed in the 19th century and early 20th century and used to stabilize roll motions in ocean-going ships. Their function is similar to control moment gyroscopes or reaction wheels in spacecraft - they provide rotational stability via production of torque. It lost favor in this application to hydrodynamic roll stabilizer fins because of reduced cost and weight. However, since the 1990s, there is renewed interest in the device for low-speed roll stabilization of vessels (Seakeeper, etc.). Unlike fins, the gyroscope does not rely on the forward speed of the ship to generate a roll stabilizing moment and therefore can stabilize motor yachts while at anchorage. Ship stabilizing gyroscopes are a technology developed in the 19th century and early 20th century and used to stabilize roll motions in ocean-going ships. Their function is similar to control moment gyroscopes or reaction wheels in spacecraft - they provide rotational stability via production of torque. It lost favor in this application to hydrodynamic roll stabilizer fins because of reduced cost and weight. However, since the 1990s, there is renewed interest in the device for low-speed roll stabilization of vessels (Seakeeper, etc.). Unlike fins, the gyroscope does not rely on the forward speed of the ship to generate a roll stabilizing moment and therefore can stabilize motor yachts while at anchorage. The World War I transport USS Henderson, completed in 1917, was the first large ship with gyro stabilizers. It had two 25-ton, 9-foot (2.7 m) diameter flywheels mounted near the center of the ship, spun at 1100 rpm by 75 hp (56 kW) AC motors. The gyroscopes' cases were mounted on vertical bearings. When a small sensor gyroscope on the bridge sensed a roll, a servomotor would rotate the gyros about a vertical axis in a direction so their precession would counteract the roll. In tests this system was able to reduce roll to 3 degrees in the roughest seas. One of the most famous ships to first use an anti-rolling gyro was the Italian passenger liner SS Conte di Savoia, which first sailed in November 1932. It had three flywheels which were 13 feet in diameter and weighed 108 tons.