Steam turbines operate at speeds up to 6000rev/min. Medium-speed diesel engines operate up to about 750rev/min. The best propeller speed for efficient operation is in the region of 80 to l00 rev/min. The turbine or engine shaft speed is reduced to that of the propeller by the use of a system of gearing. Helical gears have been used for many years and remain a part of most systems of gearing. Epicyclic gears with their compact, lightweight, construction are being increasingly used in marine transmissions.
The PAPA Class, designed mid-1960s with an epicyclic (planetary) gear system. See specs below:
2 V-5R nuclear reactors, 2 GTZA-618 geared steam turbines units
Power, h. p.
Max speed, kts
16 / 45
PAPA was designed to have a 10-knot speed advantage over US carriers and be able to run them down in the open ocean which it once did in late 1971.