Ablative armor hull generator
From Memory Alpha, the free Star Trek reference.
The ablative armor hull generator was a futuristic Starfleet technology from the early 25th century. It was designed to protect starships by generating an ablative armor hull which could withstand Klingon Negh'Var-class ship attacks and even multiple Borg cube attacks. In order to protect the ship, the ablative armor must expand across the ship's hull, except around the phasers, torpedo launchers, and warp engines from external generators mounted on the ship. The generators utilize replicator technology to create the plates for the ablative armor. (VOY: "Endgame")
[edit] Background
Here, this technology is labeled as "ablative armor hull generator" to differentiate from the ablative armor on the Defiant-class and Prometheus-class starships. There was no explicit verbal differentiation between the two technologies mentioned on "Endgame". It could therefore be speculated that the technology mentioned in "Endgame"' is an outgrowth of the ablative armor seen on these classes of vessels.
The episode never explained what happened to the ablative armor hull generator after Voyager returned to Earth. Since the presence of the technology violates the Temporal Prime Directive, the most likely explanation is that Starfleet classified it and destroyed the generator and any information about it. This is most likely the same fate of the transphasic torpedoes. However, it might also have been saved and reintroduced later when the technology reaches the appropriate time on the preferred timeline since it was introduced in the early 25th century in another timeline.
