Gypsy Class Frigate

After losing much of the Terran fleet in costly space battles with the extraterrestrial threat, the Admiralty began repurposing civilian ships into combat vessels.  The Gypsy class is derived from a standard utility frigate with class VI battle plates welded on, Proton-2 nuclear engines, rail guns, and torpedo launchers added.  While cheap to produce, it is surprisingly nimble in a fight.  Pilots do note that pushing the engines too hard tends to shake the ship apart, however.