Ablative Armour Generators

From FEInfobase

Ablative Armor Generators are powerful defensive systems introduced to Starfleet by an alternate future verson of Admiral Kathryn Janeway to the Starfleet of 2378 when the USS Voyager returned to Earth. It protects starships by generating a sheath of ablative armor plate across the outer hull of the ship. Ablative armor generators are very tempermental devices, and place a severe drain on the ship's replicator mass-stock supplies, but the added supply and maintanance headaches are more than made up for by the ability of the armor to soak up weapons fire like a sponge.

Although this technology is available to the Federation it is not currently installed on any vessels in the fleet, the costs associated with its implementation and use have been deemed far too high for Starfleet in the current climate.