Editing Steam turbine (section)

===Early development===
The development of steam turbine marine propulsion from 1894 to 1935 was dominated by the need to reconcile the high efficient speed of the turbine with the low efficient speed (less than 300 rpm) of the ship's propeller at an overall cost competitive with [[marine steam engine|reciprocating engines]]. In 1894, efficient reduction [[gear]]s were not available for the high powers required by ships, so [[direct drive]] was necessary. In ''Turbinia'', which has direct drive to each propeller shaft, the efficient speed of the turbine was reduced after initial trials by directing the steam flow through all three direct drive turbines (one on each shaft) in series, probably totaling around 200 turbine stages operating in series. Also, there were three propellers on each shaft for operation at high speeds.{{sfn|Parsons|1911|pp=26-31}} The high shaft speeds of the era are represented by one of the first US turbine-powered [[destroyer]]s, {{USS|Smith|DD-17|6}}, launched in 1909, which had direct drive turbines and whose three shafts turned at 724 rpm at {{convert|28.35| kn}}.{{sfn|Friedman|2004|p=23–24}}

The use of turbines in several casings exhausting steam to each other in series became standard in most subsequent marine propulsion applications, and is a form of [[#Types|cross-compounding]]. The first turbine was called the high pressure (HP) turbine, the last turbine was the low pressure (LP) turbine, and any turbine in between was an intermediate pressure (IP) turbine. A much later arrangement than ''Turbinia'' can be seen on {{RMS|Queen Mary}} in [[Long Beach, California]], launched in 1934, in which each shaft is powered by four turbines in series connected to the ends of the two input shafts of a single-reduction gearbox. They are the HP, 1st IP, 2nd IP, and LP turbines.