In 1994, the United States Navy launched the SC-21 program to develop a new destroyer class. Known today as the Zumwalt, it was designed to have an Advanced Gun System with a range of 83 nautical miles and highly experimental Permanent Magnet-Synchronous Motors (PMM). But that complexity meant massive research expenditures and costly delays. The ammunition designed specifically for its guns became too expensive to build at scale and was canceled outright.
The PMMs were replaced by two 34-MW induction motors instead. The Navy shrunk the planned fleet from 32 ships to three. Ambitious requirements for underdeveloped technology made this warship expensive, late, and unable to perform its originally intended mission, triggering a Nunn-McCurdy breach (ie when procurement cost overruns initiate congressional review).
