If a thruster is operating at 4 knots current, how does its thrust compare to when it operates at bollard pull?

When a thruster operates in a current, the effective thrust it can generate is influenced by the current's velocity. Bollard pull refers to the maximum pulling power of the thruster when the vessel is stationary, while operating in a current means that the thruster must not only work against the forces of resistance but also contend with the current's flow.

At 4 knots of current, the thruster's effectiveness is reduced because it has to exert additional energy to overcome the water flow, leading to a decrease in the overall thrust relative to its bollard pull capacity. This reduction in effective thrust can be quantified, and it's common to see around a 25% drop in thrust under such operating conditions.

This correlation means that as the current increases, vessels may experience significantly lower effective thrust capabilities compared to the maximum potential available when stationary, hence aligning with the claim that the thrust is 25% less than what it would be during a bollard pull scenario. Understanding this relationship is critical for ensuring accurate operational planning and safety during dynamic positioning maneuvers.