Discussion on Methods and Influence Factors for Minimum Propulsion Power Assessment

• The paper proposes a time-domain comprehensive assessment method for Minimum Propulsion Power (MPP) that includes supplementary course-keeping ability criteria, offering higher accuracy and more realistic manoeuvre behavior description compared to existing IMO guidelines. • Comparative analyses with a power line method and two steady-state equilibrium methods reveal that different MPP assessment methods have varying advantages and complexity, forming a multi-level assessment framework. • Key influence factors such as wave direction range and self-propulsion factors at low speeds significantly affect MPP assessment results; expanding wave direction sets stricter requirements, while using low-speed self-propulsion factors reduces unnecessary conservatism. • The time-domain method is particularly useful for ships that cannot meet other assessments or when additional course-keeping ability is required, providing a solution for borderline or unconventional vessels.