Galaxy class

he Galaxy-class is a type of explorer and battleship used by Starfleet in the mid to late 24th century. It is one of the largest vessels ever constructed by Starfleet.

History
The Galaxy-class began development in the year 2343 and has the dubious distinction of having the longest design, development, and construction period of any class in Starfleet history- delayed for a further year due to attempted sabotage by the Manraloth Giriaenn that was only just exposed by Lieutenant Data-, with the prototype USS Galaxy finally launching in 2357 and its first two sister ships the ever-famous Federation flagship USS Enterprise (NCC-1701-D) and USS Yamato (NCC-71807) following six years later in 2363.

During the initial planning board at Starfleet Operations, Admiral would often describe the vessel's strength as a deterrent against aggression by other powers. In stark contrast, Commodore Santin was a vocal critic of the new design, fearing that fielding a ship with such destructive capabilities might serve as a provocation to the Federation's enemies. 

Initially conceived as a class of twelve ships, once the design was finalized it was decided that only six ships would be completed, with construction on the other six halted once their frameworks were finished. The six spaceframes were then broken down into smaller segments and transported by cargo carrier to remote sites throughout the Federation, held in reserve in case a later emergency necessitated their completion.

The emergency came sooner than anyone could have realized, with the loss of 39 starships to the Borg at the Battle of Wolf 359 in early 2367. As a result of the battle, Starfleet immediately launched a massive shipbuilding and design program, which also saw the remaining six Galaxy-class spaceframes pulled from storage and completed in addition to many more constructed from scratch in an attempt to bolster the fleet's strength. While the expected Borg invasion did not come as imminently as was expected, during that time the Federation did find itself engaged in a war with another opponent: the Dominion. In 2370, the USS Odyssey (NCC-71832) became the first casualty of Dominion aggression when it was rammed by a Jem'Hadar fighter, destroying the ship. Galaxy-class ships went on to play a major part in the Dominion War a few years later, participating in numerous engagements.

In an effort to get more ships into service, many of the existing Galaxy-class spaceframes were outfitted with additional weapons and minimal crew accommodations to decrease their construction time, leaving the yards with nearly 65 percent of their internal volume empty. The 2370s also saw the introduction of several more combat-oriented designs like the and -classes into service, effectively ending the Galaxy-class's production run. 

Since the spaceframe was designed with a hundred-year lifespan in mind, the Galaxy-class will likely remain in service for years, if not decades, to come. In a possible future created by Q, the USS Enterprise was refitted with an additional warp nacelle and additional phaser arrays. The USS Venture (NCC-71854) was later modified to mount two additional phaser arrays on its warp nacelles.