NX

From Memory Alpha, the free Star Trek reference.

See also the NX class, a prototype class of starship.

NX is a starship registry number prefix in use by both the Earth and Federation Starfleets.

In the Earth Starfleet it was used to represent the NX class starships. (ENT: "Fortunate Son")

In the Federation Starfleet, they came to be used by experimental starship designs that typically became the first starship (or prototype) of their class. (Star Trek III: The Search for Spock)

The NX registry was also in use in the mirror universe to represent the NX class of starships. (ENT: "In a Mirror, Darkly")

[edit] Ships with an NX registry

Ship Name	Registry	Class	Commander(s)	Dates	Notes
none	NX-Alpha	NX class prototype	Commander A.G. Robinson	2143	First Earth ship to surpass warp 2 (ENT: "First Flight")
none	NX-Beta	NX class prototype	Commander Jonathan Archer; Commander A.G. Robinson	2143	First Earth ship to surpass warp 2.5 (ENT: "First Flight")
none	NX-Delta	NX class prototype	Commander Duvall	2144	First Earth ship to surpass warp 3 (ENT: "First Flight")
Enterprise	NX-01	NX class	Captain Jonathan Archer	2151-2161	First Earth ship with a warp five engine (ENT: "Broken Bow")
Columbia	NX-02	NX class	Captain Erika Hernandez	2154	none (ENT: "The Expanse", "E²")
USS Excelsior	NX-2000	Excelsior-class	Captain Styles; Captain Hikaru Sulu	2285-2370	First Starship equipped with transwarp (failed); registry changed to NCC (Star Trek III: The Search for Spock)
USS Constellation	NX-1974	Constellation-class	unknown	2293-2374	Registry later changed to NCC-1974 (Star Trek VI: The Undiscovered Country)
USS Bradbury	NX-72307	Bradbury-class	unknown	2366-2367	none (TNG: "Ménage à Troi")
USS Defiant	NX-74205	Defiant-class	Commander/Captain Benjamin Sisko	2370-2375	First Starfleet vessel built only for combat (DS9: "The Search, Part I")
USS Prometheus	NX-59650	Prometheus-class	unknown	2374	First starship with multi-vector assault mode (VOY: "Message in a Bottle")
USS Dauntless	NX-01-A	Dauntless-class	Arturis	2374	Decoy ship; first starship with quantum slipstream technology (VOY: "Hope and Fear")