Despite such innovations as turbo-electric drive, which converts steam energy into rotational power for turning the propeller shafts, commercial steamships have today given way to diesel-powered ships, which constitute 95% of new ship construction. Diesel engines provide a fuel efficiency of more than 50%, with a reliability at least equal to steam turbines. The Queen Elizabeth 2 (1969) was originally steam-powered, but it later was refitted with turbocharged diesel engines, which supply electric power to the propeller motors. The ocean liner has been replaced by the airplane as a means of transportation; its successor at sea is the cruise ship, which travels more slowly and functions as a vacation resort afloat rather than as scheduled transportation.
The Columbia Electronic Encyclopedia, 6th ed. Copyright © 2012, Columbia University Press. All rights reserved.