The Heavy/Mercury-class battlestars are advanced Colonial capital superbattleships/carriers of the Colonial Fleet, the most top-of-the-line vessels at the time of the second Cylon attack with a count of three in active service. This class was originally going to introduce the concept of a Superbattleship role with less Viper support and more focus on the outer Kinetic weaponry defenses. The then Rear-Admiral Nagala, the brain-child of the idea, wanted to focus more against ship-to-ship space combat without the support of Viper squadrons. Allowing the ship's heavy weapons to be the main focus of the fight without the need of CAG (Command Air Group) and Flight Decks. Though possible, the odds were against such a Battlestar to engage multiple ships at once if the situation arose, even fast attack ships en-mass proved a match. It was later given the Flight Decks, but had the number of Viper squadrons reduced to five rather than the usual 10 given to a standard Mercury Battlestar and space was given up in the secondary hanger decks to provide munition space for gun batteries. Eight years before the Cylon attack, three out of the potential five of the planned Battlestars was commissioned and construction began (this is do to lack of Colonial funding) on the designated Sovereign and her sister ships, the Translucent and the Atlantia.
The Heavy/Mercury class was introduced eight years before the fall of The 12 Colonies, the structural design of the Heavy/Mercury class differs significantly from the original Galactica and Valkyrie type battlestars, but bears more resemblance to its older cousin, the Mercury Class. The "neck" section is smaller, and the Heavy/Mercury class features eight sublight engine pods instead of the older class's standard six. Its edges are more angular, and the hull is completely armored (no exposed ribs). Each flight pod consists of two stacked landing bays with limited adjoined decks and hangars making room for extra munitions for the ship batteries and thus limiting the carrying capacity of Viper squadrons. With this, manual landing is a main procedure for all spacecraft which results in a slower Viper recovery rate. However, each flight pod also has Raptor landing bays on the sides, allowing for rapid transfer of crew cargo when docked. These pods are also 200 meters shorter and are not fixed, unlike the standard Mercury class, and do retract when executing an FTL jump, much like the Galactica class. Inside, the class features automated sliding doorways, basic computer recognition stations in vital areas, and networked computer systems through out the ship with the upgraded Command Network Program. This also includes Vipers and Raptors alike.
An example of this class, Sovereign, carries a complement of 25 Raptors and 60 Viper Mark VII and reserved 40 Mark IV fighters (three squadrons and two reserve squadrons color coded as Blue, Green, Red, and reserve squadrons Black and Yellow).
Gun batteries on the Heavy/Mercury class are distributed all over the ship, with the greatest concentration of large turrets found along the side of the ship, within the valley created by the upper and lower halves of the hull, and along the flight pods, like the standard Mercury Class. Six twin-turrets are mounted on the underside of the upper hull on the ship's bow, below which sits six non-twin-turreted large guns along with four twin-mounts mounted in front of the nose; these form the main forward gun batteries. Eight twin-turrets are mounted on each underside of the "alligator" head, grouped in pairs. There are also two twin-mounts on the side of each flight pod along four more twin-turrets mounted on the front and back of each flight pod. This amounts to a total of 48 main gun batteries, 12 more than the Mercury Class and also increasing the ships length. The turreted guns of the Heavy/Mercury class have a equal rate of fire like the Mercury Class, but a much higher rate than the Galactica and Valkyrie class turreted guns when operating in flak mode.
The standard crew complement of a Heavy/Mercury class battlestar is in excess of 2,200 (300 less than a Mercury Class), a very small number for a ship its size made possible by computer automation.
The Heavy/Mercury class battlestar also does not have a Viper constructional facility to accommodate new Vipers to a fight.