The NX-03 was a Template:ShipClass starship for the United Earth Starfleet that was on the drawing boards in 2151. (ENT: "Fortunate Son")
The Pocket ENT novels Kobayashi Maru and Beneath the Raptor's Wing depicted the manufacture of this ship, the Challenger.
She was launched in August, 2155, alongside Discovery NX-04, and was destroyed the next year when Captain Roy Dunsel (Roy Dunsel at Memory Beta, the wiki for licensed Star Trek works) activated the ship's self destruct, the first one installed aboard a United Earth starship, to destroy a Romulan Warbird before it could attack Andoria.
Template:NXClassStarships