The Andromeda Class was initially conceived as being the center piece for the Explorer Program (a deep space exploration endeavor founded my members of the Consortium for Interstellar Exploration, these same members would eventually form the United Federation of Planets). The Andromeda Class involved the melding of many advanced concepts for ship's structure and design, warp dynamics, sensor engineering, and power management. The great hope was to create an interstellar fleet to explore the deepest reaches of the galaxy (as defined by mid 22nd century mapping). However, events would preclude the original concept due to increased tension between members of the CIE and the Romulan Republic. Though the Romulans allowed an independent system within the Republic to particpate in the program, the obvious agenda was to maintain an avenue to build relations with the Vulcans and keep track of the Terrans. As the overlapping regions became more unstable, several incident occurred that represented a threat to the security of CIE colonies, settlements, and trade routes. An agreement was made to arm the Andromeda Class with high-impact phase cannons and photon torpedoes, but as the situation with the Romulans became more perilous, it was finally decided to redesignate the Andromeda. The fledgling Starfleet recognized the need for a command and control ship for fleet operations. The unique senor capabilities and versatility of the Andromeda Class made it a favorable platform for this role, and with this designation to the Fortress Cruiser, the final armament request was authorized: long-range missiles (capable of carrying multiple photonic warheads or the chambered fusion device, aka the "planet devastator"); warp capable fast corvette strike craft; and sub-light aerospace fighters (eventually replaced by the first generation of warp capable Aerostar). The Andromeda, initially used as a support/command ship during the early part of the war, eventually became the lead vessel for fleet operations. Its presence at critical moments during a campaign enabled Starfleet to defeat numerically superior Romulan fleets due to the long-range sensors and the devastating impact of the missiles and strike craft.
Eventually, the newly established United Federation of Planets authorized Starfleet to improve the capabilities of the Andromeda, which lead to the third and fourth generation. The expansion program was nearly as resource intensive as the initial building. The improved Andromeda boasted an extended long range sensor system and missile system, improved strike corvettes and more versatile Aerostar fighters. The phased cannons were replaced the a one-of-a-kind track phaser cannon. The long surface structure housed a magnetic track for the high output phasers and also allowed for more efficient power transfer to the phaser cannons. This phaser concept partly lead to the development of planar phaser arrays in the 24th century.
The original dream for the Andromeda would not be seen again until the development of the Galaxy Class, a new generation of Explorer ships. Its development was marred by the unfortunate realities of interstellar conflict, but its impact on the Alpha quadrant would shape the interstellar society of the 22nd and 23 century.
The graphics show the original Andromeda class (post Fortress modifications); an interior cross section for the 2nd generation (excuse the paintbrush blocks due to enlargement); and the improved Andromeda class, which served during the mid to late 23rd century.