A starship originally designated NX-2000, for testing purposes and as the first of its class, "The Great Experiment" was the first starship equiped with transwarp drive.
During the NX's trial runs, the transwarp drive propulsion system presumably had to be removed due to its failure (although this is never shown in the feature films). When the starship entered operational status, its registry number changed to NCC-2000. This Excelsior was under the command of Captain Hikaru Sulu for a three year mission studying gaseous anomalies.
Excelsior was an integral part of the Khitomer Peace Conference of 2293.