Propulsion System

Thrusters are used for station-keeping, alone or in combination with mooring lines.

Thrusters can be divided in two main categories:

  • fixed-direction thrusters and rotatable thrusters

  • azimuth thrusters.

An azimuth thruster can usually rotate \(\mathrm {360^\circ}\) about the vessel’s vertical axis. In SIMO a fixed direction thruster is allowed to give a negative force, while an azimuth thruster always gives a force which is non-negative.

Further, a thruster can be

  • open

  • ducted (nozzled)

Although this distinction is reflected by the type designations for thrusters in SIMO, see Body Data Specification in the SIMO User Guide, it has no effect on the computation of thrust: A thruster’s behaviour is characterized by its coefficients of thrust and torque, which implicitly reflect whether it is open or ducted. In other words, the open/ducted property is not used internally inside SIMO.