NX-Delta

From Memory Alpha, the free Star Trek reference.

The NX-Delta was a Human space vehicle in operation in the 22nd century. A test vehicle for the warp five engine, NX-Delta was the fourth vessel of the NX test program.

In 2144, months after Jonathan Archer and A.G. Robinson's illegal flight with the NX-Beta, the NX-Delta, piloted by Duvall, became the first Human spacecraft to break the warp 3-barrier. (ENT: "First Flight")

NX-class starships
NX prototypes: NX-Alpha • NX-Beta • NX-Delta
Commissioned ships: Columbia • Enterprise
Mirror universe: ISS Avenger • ISS Enterprise