Methods and systems used or pro nosed for stopping large vessels are reviewed and a theoretical analysis of their behaviour made, This indicates finite limits to how successful any economic design of stopping device can be. A new thrust reversing device was conceived and a research programme was devised and carried out to evaluate its performance. A model of the rudder brake ( l/l00th size of the rudder fitted on a 250,000 tonnes dwt. tanker) was manufactured for wind tunnel and tank experiments. This model was tested in the wind tunnel to determine its drag coefficient for various design configurations and its ability to generate lateral force and drag when inclined to the direction of flow of and thus provide some source of controlled steering whilst braking. The model was then rested on a self-propelled stationary/ model in the experiment tank to determine its performance characteristics for various design configurations, distance from the propel1er and propeller rate of rotation. Stopping manoeuvres were carried out with the self-propelled model using the best design configuration of the rudder brake from various initial speeds. The model tests show that the design produces an almost constant retarding force (independent of model speed).At any given speed this force is made up of a combination of drag effects plus reversed thrust effects. The former die away as speed is reduced while the latter increase to provide the constant force. At zero speed the device provides a reversed thrust sufficient to allow the vessel to proceed astern and thus there would be no need for making provision for reversing the main engines9 which is a relative expensive item on all. ships at present. The overall performance of the rudder brake device appears to be better than any existing or proposed stopping arrangements and in view of the experimental evidence, a patent was taken out on the device in September 1974.