The Japanese invention can cut the rolling of ships by up to half and can easily be fitted to both cruise ships and car ferries. The Hybrid Anti-Rolling System (HBARS) has already been tested in open water on the Mirai, an oceanographic research vessel built for the Japan Marine Science and Technology Center of Tokyo. From waves up to 4 metres high, which are considered rough, to typhoons where the waves are as high as 17 metres, it reduced the rolling and also improved the ship's manoeuvrability.

HBARS, which was developed by the engineering company IHI in Tokyo, has a 100-tonne mass of metal mounted on rails. Sensors measure the motion of the ship and feed information about the roll to a central computer, which controls the movement of the counterbalance by means of electric motors.

The motor has two roles. One is to decrease the speed of the mass while it is moving relatively quickly, such as in the middle of the roll, and the other is to speed up the mass when it is moving too slowly to damp the motion effectively. When the mass is being slowed down, its kinetic energy is transformed into electricity to save energy. According to IHI, this makes HBARS ideal for ships with limited power supplies, including passenger and car ferries.

More information: New Scientist, 12 June 1999