Ship's Rating is a value which refers to the tactical speed of a spelljamming ship. It is determined by the propulsion, usually a Helm, which draws power from the strength of its helmsman. Each point of SR translates into 500 yards per round of tactical speed.
The following items or additions affect SR:
SR has no effect on a ship's maneuverability.
If playing 3rd Edition or higher, you may refer to SR as Tactical Speed (TS) to avoid confusion with Spell Resistance (SR).