From Jackill's Star Fleet Reference Manual-Ships of the Fleet, Volum II - by Eric Kristiansen

Notes:
        The Firestone Class of large combat vessel was one of many designs that reflected the Star Fleet Federation policy change towards multi-mission military vessels. The Firestone was originally designed as a Dreadnought, intended to replace the Federation Class, which was in the process of being updated. But military action along several Federation boarders prompted Star Fleet Procurement to begin re-evaluating the design. Although most research was conducted near secure or established boarders, the expansion of the frontier continued to create danger for many exploratory starships that we considered underpowered or under-gunned to explore hostile areas. With a large number of front line vessels being built, it was felt that the flexibility of Heavy Cruisers would best allow the Federation to explore and continue it’s charter. But established boarders, such as the Tholian and Klingon boarders, were still a heavily volatile area.
        New combat vessels abounded, but Star Fleet felt that heavier combat Cruisers would better fill the niches being vacated by the Heavy Cruiser fleet. To this end, many new combat Cruiser designs were constructed. Nearly all were designed to conduct research, all-be it to a limited degree, in a hostile area, while maintaining the ability to deal with threat forces and support other patrol vessels in the area. The Firestone benefited from the near disastrous commissioning of the Menahga Class, which proved an unpopular Class until conflict proved it’s worth. The Firestone, like many similar designs, was built around several large labs, which we closely integrated into the combat and support systems. Although this original design was successful on some Classes, it was less popular on other Classes. But the Firestone continued on its design track, incorporating many of the more successful ideas already established in other designs.
        The Mk I was designed around a basic tri-engine drive system, which was still being perfected in the early 2270’s. To help incorporate the science labs, a specially designed secondary hull was built which housed 4 of the large vessels 8 labs near the connecting dorsal. This gave science and engineering crews direct access to the torpedo tubes, allowing them to quickly modify and incorporate a multitude of sensor probes. To prevent loss of combat ability in the event of a major science catastrophe, a second suite of torpedo banks was added to the lower part of the secondary hull. Although somewhat vulnerable in this location, the dual torpedo banks gave the Firestone Class a tremendous punch, allowing massive torpedo strikes against multiple enemy targets. The Mk I also incorporated two FMH-2 mega phaser emplacements. Originally, the vessels was slated to have the two cannons and third engine housed in a “roll-bar” housing, similar to the Miranda or Comanche Class. But the addition of the secondary torpedo tubes and location of the drive engines necessitated a lower profile location for the third nacelle. When the nacelle was lowered, it was decided to mount the cannons away from the warp drive. This reduced interference with the drive system when the cannons were used. The Mk I was such a successful design, that it remained unchanged for nearly 15 years. In 2288, the decision was finally made to upgrade the powerful Cruiser. The Mk II saw the introduction of the FSS defense system. More powerful than the FSP, the FSS was fast becoming the standard in Federation shielding. The Mk II also incorporated an M-7a computer. The Mk III would also incorporate a new computer core design, as well as an increase in overall firepower, which would server Star Fleet well during the conflicts with the Romulans. The Firestone were constructed at the Izar Bekkaas Military Installation. Original production was slated for 3 per year, but production difficulties with the tri engine design allowed for only 2 to be commissioned per year.
        Currently, there are no major plans to introduce a MK IV, although Star Fleet Procurment is believed to be interested in updating the design to replace recent ship losses. Of the 30 commissioned, 29 remain in active service, all of which have been converted to the Mk III design. The Mk II USS Yang (NCC-8610) was lost while mapping the Eridani VII Comet near the Romulan Boarder. Although unconfirmed, it is believed that Romulans, using captured and upgraded Klingon vessels attacked the Yang as it was heading towards Outpost 7. Debris from the site of battle and survivor testimony indicates that at least three enemy vessels were destroyed, all of whom indicate Klingon, Romulan and Orion technologies. Star Fleet continues to analyze the data.