Into the 5th millenium, the UAS Federal Navy once again foresaw the need for a class of warship capable of delivering an overwhelming amount of directed firepower into a conflict. Such a vessel would operate in the same Task Groups as the Evolution-class Supercarrier, itself a powerful warship, but falling short of what Naval commanders saw as a "Check Mate Move" asset.
The result of twenty cycles of development, trials and upgrades resulted in a candidate for such an asset. Based on the same underlying hull-design as its sister class, the Evolution, the RT-AX "Retribution II"-class Dreadnought is an entirely new breed of super-capital class for the UAS Federal Navy. Drawing from lessons learned in the "Dreadnought" era of the late 3rd and early/mid 4th milleniums of the Old Federation, itself a re-occurance of the "Big Gun" battleships of Ancient Old earth in the 19th century; the Retribution II has one simple purpose: complete battlefield domination, the last word in directed firepower available to the UAS Fleet. RT-type dreadnoughts are the second major terran class to bear the name "Retribution", she is named in honour of the pre-fall Retribution-class Battlecruiser; the ancestor to the now legendary Endeavour-class, still in service with the Aquarian military, some thousand cycles later.
To acheive that goal, the EV-AX's superstructure was entirely stripped back to the base design, hangars and their internal support facilities were removed; being replaced by banks upon banks of additional - and redundant - capacitor arrays, cargo modules replaced with enhanced and upgraded shield modulators. The outer hull layers have entirely new armour protection; up to 15M thick in primary belts, using the most advanced non-ferrous nanoalloys available to terran manufacturing.
But, perhaps the largest improvement to internal systems on the RT-AX - to support her collossal firepower - is the new Reactor System: the 'X115 Array' or otherwise known as the 'Supernova'. Itself a development of the Evolution's own X104 Reactor, the X115 incorporates the latest innovations in Terran and Alien technology to create the highest density energy output ever installed on a mobile space-faring vessel in known human history.
Despite a similar outwardly appearance; RT-type dreadnoughts retain most of the EV-type carrier's electronic systems, including a second-generation SPARTAN targeting system, there is one major upgrade that defines the new Retribution class.
Specifically developed for this class, RT-type's main forward turreted battery has been upgraded from the quad-A battery on the EV-type carrier, to a singular A+ type main battery. The A+ designation for a turreted battery is entirely new, and developed alongside the Retribution II: no other vessel in the Aquarian fleet is large or powerful enough to support this gargantuan weapon system.
The A+ Designation, dual, dual-linked IM353 Ion Maser Particle Accelerator Cannon, or IMPAC, sometimes refered to as "Impact" by gunnery crews for its devestating firepower. The IM353 IMPAC is the single largest turreted armament ever installed on an Aquarian space-faring warship, and is roughly equaviliant in energy output to the main, axial-armament of a Sleipnir-class Heavy destroyer; except with 360 degree traversal and twice the re-charge capability.
All of these massive changes have resulted in an extremely heavy warship, weighing in at just over 4 megatons, RT-type dreadnoughts are the heaviest vessels ever deployed by the Aquarian military, surpassing even the legendary 'Revenge'-class Battleships of the late 3rd millenium. As a result, Retribution II is not a fast warship, the drive system has seen minor improvements from the first-generation array on the Evolution class, but is otherwise fundamentally the same system. The enormous increase in mass and density prevents RT-type dreadnoughts from safely reaching the same Impulse and Cruising speed as their carrier-class sisterships, if the ship's captain wanted to change course in a reasonable amount of time.
Field trials of the S1 Designation were successful, but the UAS Federal Navy requested some major additions to the design. Although originally designed as a Stand-off warship, the Navy updated its requirement for a more universal combat platform, and as such A.R.A.S Shipyards immediately began working on a revised model with the new specifications in mind. the updated requirement called for increased A-type forward battery, capable of mounting IM85 Ion Masers, and the brand-new Third-Generation SPARTAN missile system that was just becoming available. S1As also utilise an upgraded PDS armament. The S1A designation will deploy with the fleet and all current S1 variants will be returned to dry-dock and upgraded to S1A designation.
Retribution II-class 'S1A' Dreadnoughts are expected to enter full deployment before the turn of the 45th century.