The yard continued to be mainly a repair facility with a steadily increasing workload. The new 750-foot Dry Dock 2, authorized three months after the sinking of _Maine_, was built to receive the Navy’s biggest ships. But soon after the massive structure’s 1905 completion, Britain launched H.M.S. _Dreadnought_, ushering in an even larger class of battleship the dock could not accommodate.
In this period the yard specialized in the smaller battleships and the newest type of warship: destroyers. These fast, versatile ships had evolved from British “torpedo boat destroyers” built in the 1880s to counter the new torpedo boats. The mobile torpedo, also developed in Britain, was a self-propelled explosive device launched from a warship’s deck, traveling underwater to open the hull of its target.
Developments in naval technology from the 1880s to the eve of World War II included nothing quite so dramatic as the epochal shifts from sail to steam and wood to iron, but the period saw advances in strategic weapons such as submarines and aircraft carriers, and major innovations that resulted in ships and shipbuilding essentially like what we see today. In the period before the age of flight, sophisticated warships were highly visible embodiments of the state of a nation’s technology, and the rapidly expanding U.S. fleet was an unmistakable sign of its growing industrial and technological prominence.
[Illustration: _Charlestown’s machine shop in 1913. Overhead belts transferred power from a central steam engine to the machines. The potentially hazardous belts were later replaced with electric motors on each machine._]
[Illustration: _Lathe operator shapes steam turbine rotor for destroyer tender Whitney in 1923._]
The major innovations were again in hull material and propulsion. The transition from iron to steel hulls further liberated naval engineers. Lighter, stronger, and less brittle, steel allowed them more play in hull size and proportions. Despite extensive use of ironclads by the United States during the Civil War, its navy essentially skipped the iron stage in seagoing warships, moving from _Hartford_-type wooden steamers to the steel ABCD ships of 1883. While the Charlestown yard launched no steel warships until the 1930s, it did construct the tug _Pentucket_ (1903) and training bark _Cumberland_ (1904), both steel-hulled.