The NX-Delta was the third prototype vessel used in the NX Project in an effort to test and refine Henry Archer's warp 5 engine design.

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

NX-class starships
NX prototypes: NX-Alpha • NX-Beta • NX-Delta
Commissioned ships: Enterprise NX-01 • Columbia NX-02 • NX-03 • NX-04
Mirror universe: ISS Enterprise NX-01 • ISS Avenger NX-09