This paper reports on the investigation and development of flywheel technology as energy storage for shipboard zonal power systems. The goal was to determine where energy storage devices could improve operation and/or reduce life-cycle maintenance costs. Applications where energy storage can provide benefits include uninterruptible power to essential loads, "dark" start capability, load leveling, system stability and pulse weapons. A flywheel energy storage system (FESS), with 25 kWh of available energy, is presented as an alternative to the current shipboard electrochemical battery system, highlighting the advantages for and challenges presented by shipboard applications. Flywheel technology overcomes some of the shortcomings of today's energy storage systems by having an extremely high cyclic-life, limited temperature sensitivity, no chemical hazards, charge rate equal to discharge, and reduced weight and space. As gas turbine electric starter development enters into fleet evaluation, FESS may provide dark ship start capability more so than any other systems being investigated. This paper discusses the critical technical challenges of the FESS for shipboard systems, and the steps for future development.