In the canon Star Trek Universe, the threat to the Federation posed by the Borg and the Jem'Hadar forced them to consider for the first time, a ship whose purpose was wholly based on military capability.
As a former member of the military (US Navy), it makes perfect sense to me for the Federation to avoid creating battleships, i.e. large ships designed primarily for combat. They don't make them for the same reason we don't in the Twenty-first century. The laws of diminishing returns in combat.
While cost of production is not necessarily a factor, time to produce is. If I can make six Defiant-class ships in the same time as it takes to make one Cruiser class ship, I will always take the six ships over the one. Especially if the damage dealing capacity of that one ship is half that of the Defiant class ship. Same number of crew are required, but I have six nimble targets for the enemy to shoot at and six ships capable of attacking opponents.
Since the weaponry of the Federation is both powerful, and easily able to fit on almost any ship (as long as it has a warp core power plant) there is no rationale for placing weapons on a single ship which might be more effective being spread out over a half dozen ships.
The factor of size is negated if you are not able to protect that ship from attack effectively. The reason the Borg get away with such immense ships, is their resilience to damage in combat. Alpha Quadrant races depend far more on shields than they do on redundant systems or sheer mass to overcome their enemies.
Size limits the ability to coordinate technology effectively, the larger the ship and crew, the slower the coordination; Borg ships evidently benefit from their hive mind intellect enhancing their overall combat performance. In this case, a ship is only as effective as the minds coordinating it or the technology protecting it.
Technical Analysis of the Federation
- Despite their protestations to the contrary, the average Federation starship was, despite its addition of scientific and exploratory technology, quite a capable weapon of war.
- Armed with multiple phaser arrays or banks, photon torpedoes launchers and effective defensive shielding, the average Federation cruiser was more than a match for any other single type of cruiser from most of the Alpha quadrant races. In groups or small fleets, they were more than equal to most races of the Alpha Quadrant.
This balance of power changed when the Borg arrived.
With their Cube ships, each one was filled with redundant power systems, multiple weapons systems (torpedoes, cutting beams), layered defensive arrays and powerful tractor beams (all systems used by the Federation but with the Borg strategy of filling their ships with multiple and redundant systems).
Each Borg Cube was strategically capable of destroying entire Federation fleets simply by being able to absorb incredible amounts of fire power and still being able to destroy one ship after another with their increased rates of fire.
The Borg could also adapt to shield signatures, rendering a ship's shields inoperative, and with their superior firepower tear it apart in seconds. This usually only took one or two attacks unless the ship rotated their shield frequency continuously.
Add to this their ability to adapt to a particular attack and be unaffected after a time, and you have an enemy whose ability to deal destruction was unmatched in the Alpha Quadrant. No race could have stood against them for long.
To this end, the Federation designed two experimental warships:
Defiant Class Starships: an escort sized vessel with phased cannon arrays, quantum torpedoes and defensive armor as well as enhanced mobility made it more than capable of dealing damage equivalent to that of a Galaxy-class starship. Her armaments included:
- 4 x Class I rapid fire phaser pulse cannon
- 3 x Phased Beam Emitters, 2 forward, one aft, standard phaser array
- 6 x Pulse fire Quantum/Photon torpedo tubes + 100 torpedoes fourforward, two aft
- 1 x Probe / Photon torpedo launcher - equivalent to standard photon torpedo tube + 20 torpedoes
- Auto modulated high capacity shield system, total capacity 2,376,000 TeraJoules
- Heavy Duranium/Tritanium double hull plus 20 cm Ablative armour.
- High level Structural Integrity Field
This was a warship, pure and simple, designed to deal out damage in all directions with variable phasers which could vary their frequency preventing the Borg from easily adapting to them and Quantum torpedoes who damage capacity eclipsed the photon torpedo by orders of magnitude; same box, much bigger bang.
Prometheus Class Starships: A slightly larger than cruiser-sized vehicle, the Prometheus was a warship whose full capacities were never shown fully on screen. It was equipped with armaments similar to the Defiant and could split into three separate vessels tripling their firepower and offensive capacity (multi-vector assault mode). It also had multiphasic, regenerative shielding, and ablative armor
Armament, Docked Mode
- 12 x Type XII Phaser arrays
- 2 x Pulse fire quantum torpedo tubes + 290 torpedoes
Armament, Separated Mode
- 6 x Type XII Phaser arrays
- 2 x Pulse fire quantum torpedo tubes + 115 torpedoes
- 4 x Type XII Phaser arrays
- 3 x Pulse fire quantum torpedo tubes + 175 torpedoes
- 8 x Type XII Phaser arrays
- 18 x Type XII Phaser arrays
- 5 x Pulse fire quantum torpedo tubes + 290 torpedoes
This also does not invalidate the increasing of firepower on larger Cruiser and Galaxy-class ships with phase cannon arrays, quantum torpedo tubes in addition to photon torpedoes and multiphasic shield arrays. With the addition of the transphasic torpedo (claimed from a future alternative timeline by Admiral Janeway for use against the Borg) the Federation would once again be a power to be reckoned with in the Alpha Quadrant.