Ablative armor is a type of protective hull plating developed by Starfleet sometime on or before 2371. (DS9: "Past Tense, Part I")
- According to the Star Trek: Deep Space Nine Technical Manual, ablative armor was designed to disintegrate at a controlled rate under directed energy blasts, providing an additional layer of defense for starships.
Sometime in 2371, after her deployment to Deep Space 9 and unbeknownst to Starfleet Operations, ablative armor was added to the USS Defiant. (DS9: "Paradise Lost", "The Way of the Warrior", "The Changing Face of Evil") This armor was first seen in use protecting an unshielded Defiant against Klingon disruptor fire. Throughout many conflicts in the 2370s, the armor protected the Defiant from, among others, the Klingons, the Cardassians, the Dominion and even from Federation phaser fire. During the failed coup attempt by Admiral Leyton, Captain Erika Benteen explicitly credited the Defiant's ablative armor with thwarting attempts by the USS Lakota to disable and prevent the Defiant from reaching Earth. (DS9: "Paradise Lost") By 2374, ablative armor had been installed on at least one other advanced Starfleet combat vessel, the USS Prometheus. (VOY: "Message in a Bottle")
It is of note that under certain conditions, chroniton particles generated by Romulan cloaking devices can become lodged in the ablative armor matrix. On at least one occasion, a temporal surge caused by the explosion of a microscopic singularity shifted the chroniton particles in the hull into a high state of temporal polarization, this caused a transporter beam to be redirected through time. This caused Commander Benjamin Sisko, Doctor Julian Bashir, and Lieutenant Jadzia Dax to be sent back in time to 2024, just before the Bell Riots. (DS9: "Past Tense, Part I")
The Borg's long-range tactical vessels were also equipped with ablative hull armor. (VOY: "Drone") The Hirogen outpost, designed as a training facility by means of holodeck technology, utilized three layers of ablative armor to protect the grid's holoemitters. (VOY: "Flesh and Blood")
- Though unclear, this armor is likely related to the ablative hull armor technology, brought back from 26 years in Voyager's future and used by the USS Voyager. (VOY: "Endgame") As there has never been an explicit differentiation between the two technologies, it could be speculated that the future armor technology from the 25th century is an outgrowth of the ablative armor seen in the 2370s.