From the Obsidian Fleet website:
Miranda Class Starship
Expected Duration: 120 years
Time Between Resupply: 1 year
Time Between Refit: 4 years
Enlisted Crew: 280
Cruising Velocity: Warp 7.6
Maximum Velocity: Warp 8.8
Emergency Velocity: Warp 9.4 (for 12 hours)
Length: 243 metres
Width: 150 metres
Height: 63 metres
Type 7 Shuttle: 2
Type 8 Shuttle: 3
Argo Transport: 1
Type IX Array: 6
Type VIII Array: 4
Burst-Fire Torpedo Launcher: 4
Photon Torpedoes: 190
Quantum Torpedoes: 95
Polaron Torpedo: 15
These are the specifications for the standard rollbar-equipped Miranda. Rollbar contains two forward torpedo launchers, two aft torpedo launchers and torpedo storage.
NOTE: The specifications of the USS Portland differ slightly than the typical Miranda class vessel. We do not have Marines or Fighters. In their place, we have space to test out new experimental technologies under development by Starfleet.
In 2278, Starfleet decided that it needed to replace her ageing Poseidon class starships with a brand new Destroyer vessel, one which would have a similarly long life span within Starfleet and also serve as both a major tactical vessel and also to be a strong explorer vessel with major Multi-role capability. The design brief was then handed out across the Federation and over the next year, initial proposals began to arrive for what Starfleet had termed her “Future Multi-role Starship” Programme and by the deadline, Starfleet had fourteen separate options on her table. In the end however, the Advanced Starship Design Bureau elected to use a concept from the design company responsible for the original Poseidon class, Yoyodyne Starship systems and the clear design lineage was obvious to most who saw the new Miranda class, as she was termed. Indeed the design lineage was so clear, that the Klingon and Romulan Intelligence Services initially thought that Starfleet had merely refitted her older Poseidon class vessels.
Therefore in 2279, the design progressed to the next phase, where Starfleet’s Advanced Starship Design Bureau sat down with Yoyodyne and planned out intensively the Starships systems, spaceframe and internal arrangement and once the process was complete, the keel was laid at Starfleet’s Sherliosh Fleet Yards in orbit of Tellar Prime. The ship was finally ready for Fleet Trials after fifteen months of production and the USS Miranda was launched into some very extensive Trials, which fortunately for the designers, went very well.
The Miranda class was initially tabled for a production run of 32 vessels, over the course of 4 years and the design would continue to serve in Starfleet, being produced at a steady rate without refit until the early 2300’s, whereupon in 2311, when in the aftermath of the Tomed Incident, Starfleet elected that the Miranda class should undergo a major refit, improving her tactical systems and installing a new pair of warp drives and boosting her warp speed. Her sensors and interiors also got a major refit. This then enabled the Miranda class to continue into production for another fifteen years, by which time there were over 200 Miranda class vessels in production.
It was then that Starfleet realised the versatility of the Miranda class chasis and the readiness with which it could be produced by Federation Fleet Yards, which had been churning them out at a steady rate for over 40 years. This lead to a large number of Miranda class variants coming into service, with them being converted to serve as anything from civilian and Starfleet operated Cargo ships (Anton class), to Medical ships (Phlox class) an enhanced Tactical variant (Reliant type) was even created to serve with Federation forces.
The Miranda class and her variants therefore came over the intervening years to be a common sight across the Federation and were a major target of foreign espionage, due to the fact that many Miranda class hulls which had never been completed were used as testbeds for specialist systems and prototypes. It was again as a result of rising hostilities with both the Cardassian Union and subsequently the Talarian Patriarchy lead to a number of small refits of Miranda class vessels, giving her a lot of new tactical systems, sensors, defensive systems and propulsion systems. This lead to the existing Miranda class variants being continued in service well past the 2360’s, much longer than her designers had realistically hoped possible, despite her tabled shelf life of 120 years.
The 2nd Federation Klingon War and then the subsequent Dominion War lead to the loss of a large number of Miranda class and Miranda variant vessels, taking the total Miranda type vessels in service from nearly 400 to just 120. Many within Starfleet felt that the time had come to begin retiring the Miranda class, however, given the cost of replacing her with comparable vessels in the aftermath of such a long and sustained conflict, Starfleet elected instead to maintain the Miranda class in service. The Fleet Review of 2386 again caused into question the life of the Miranda class, most of the hulls of which were now coming up on their end of life dates. However instead of again retiring the Miranda class, Starfleet fitted her out with the latest power and data transfer systems, updated sensor and communications arrays, upgraded phaser arrays, new shield generators and a thicker layer of ablative armour. Her internals were also totally reworked as a result of the power transfer and computer upgrades needed to support the new systems, which enabled Starfleet Engineers to bring Miranda class vessels up to standard internally. Undoubtedly the upgrade programme begun in 2386 was the most ambitious ever embarked upon and some analysts predict that the comprehensive nature of the upgrades may enable the Miranda class to serve beyond her predicted shelf life, perhaps even for another thirty or forty years.