X-303

The X-303 was an interstellar spaceship built secretly on Earth using technology procured by Stargate Command.

Like its predecessor the X-302, the X-303 is exclusively of Terran construction, but incorporates a number of alien technologies, including inertial dampers, artificial gravity and an antigravity system that allows the vessel to hover in midair. Its rockets are capable of boosting it from the surface into orbit in less than thirty seconds, and the ship incorporated a larger version of the Naquadriah-based hyperdrive developed for the X-302. The version incorporated into the X-303 included a buffer designed to compensate for Naquadriah's inherent instability.

The most notable difference between the X-303 and its predecessor is in side. Whereas the X-302 was designed as an air and space superiority fighter, the X-303 was designed instead as the U.S. Air Force's first capital ship. Spanning several decks and capable of carrying more than a hundred personnel, the X-303 could in fact contain eight X-302s within its hangar bay.

History
The X-303 was constructed in an underground hangar facility designated Area 37-92/NV, in a project named "Prometheus." Its development was so large an undertaking that maintaining its secrecy proved impossible, with information leaking to reporter Julia Donovan with the Inside Access news program. In an attempt to minimize the potential damage of the project's disclosure, the President of the United States agreed to give Donovan, her producer and a camera crew a tour of the X-303, claiming the alien technology it incorporated was in fact salvaged from a UFO that crashed near Fairbanks, Alaska in 1978.

During the tour, the ship was taken over by the camera crew, actually rogue NID agents working at the behest of Colonel Frank Simmons. The agents successfully managed to steal the ship and take it into hyperspace before being overpowered by SG-1. However, the hyperdrive, which was configured for Simmons by the Goa'uld inhabiting Adrian Conrad, malfunctioned and transported the ship instead to an unknown destination.

In what came to be the ship's first mission, the Asgard took the X-303 to their home galaxy in hopes that it could be used to trap the Replicators inside a time dilation field. During this mission, the Asgard also modified the Prometheus' shields and engines to their maximum potential, correcting the faults in the vessel's hyperdrive. After the successful completion of this mission, the Asgard provided shields and weapons for the ship in advance of its formal shakedown cruise as a gesture of gratitude.

Ultimately, the X-303 entered active service, taking the designator BC-303 and the name Prometheus. In this capacity, it served as the flagship of the Tau'ri fleet under the auspices of the Office of Homeworld Security, and received additional upgrades from the Asgard. Though plans were made to construct additional ships of the class, the introduction of the Daedalus-class battlecruisers rendered the BC-303 obsolete, leaving the Prometheus as the sole vessel in its class.

The design plans for the X-303 (without the Asgard upgrades) were provided to the Russian Federation in 2002 along with those for the X-302; however, the Russians have apparently not constructed any such vessels.