Sovereign Class Ablative Armor
Originally developed in 2367 during the Defiant Class Development Project, ablative armor is still considered to be a significant breakthrough in starship defense by effectively creating a beam-retardant layer that greatly increases a ship's life expectancy in battle. Originally deployed only on ships of the Defiant class, ablative armor showed remarkable dispersion properties against various beam-type energy weapons, including the various types of phaser, disruptor, polaron, and focused-plasma beams employed by nearly all threat races. The armor works by first dispersing incoming beam energy across the hull of the ship where, after reaching an undisclosed threshold, causes part of the armor to boil away, taking with it a large fraction of that energy. The effect also creates a modest vapor cloud, which effectively disperses the incoming beam further, causing it to do less direct damage to the hull. It should be noted, however, that the armor is not a hull replacement, but a supplement and must be replaced over time due to the boiling away process.
Because of the tactical nature of the Sovereign class, Starfleet Command requested that the ablative armor be used to supplement the defenses of its new flagship class. Initially considered to supplement the majority of starship classes, production complications and long fabrication time makes the usage of the armor limited to warships and high-risk classes, resulting in only limited usage around vulnerable areas of Galaxy and Akira-class starships and almost-total body coverage of the Defiant and Sovereign. Encounters with the Borg had already proven their ability to penetrate Federation shielding on, at that point, two occasions - the U.S.S. Enterprise-D's encounter at system J-25 and again at Wolf 359. It was then only natural that the design team saw the need to outfit the Sovereign with this additional layer of defense should the Borg or other threat races find a means of penetrating the regenerative shielding.
Each Sovereign-class vessel is equipped with an average depth of 10 centimeters of armor hull-wide, which can be replaced as wear permits at select fleet yards. Due to the supply demands, repairs made to the hull of a starship in the field will lack the extra layer of armor until the vessel is able to dock at a facility with spare plating.