Abstract
Free running manoeuvring trials of an unmanned surface vehicle were performed to investigate the effects of cross flow at the inlet of the waterjets powering the vehicle. Circle, straight-line and turning manoeuvres were performed. A data acquisition system was developed to simultaneously measure the thrust developed by the waterjet and the vessel’s position, speed, and heading. The longitudinal and cross flow at the inlet of the waterjet was estimated from the speed and heading measurements. It was found that the presence of cross flow correlates with a drop in the thrust developed at the waterjet.