Prototype is the common designation for a first working model of a new invention, used for trial runs.
In 2373, Starfleet Science developed a prototype of a device called a polaron emitter, designed to expose Changelings by rendering them unable to maintain solid form. The untested nature and the complicated means of placement and activation made Miles O'Brien remark: "I hate prototypes". (DS9: "Apocalypse Rising")
Concerning starships, Starfleet prototypes had an "NX" prefix in the registry number, as opposed to the normal "NCC" (this was different from the United Earth NX prefix, which indicated the NX class), and were typically the first vessels in their class.
- USS Bradbury
- USS Dauntless (actually an alien vessel in disguise)
- USS Defiant
- USS Galaxy
- USS Intrepid
- USS Nova
- USS Prometheus
- USS Sovereign
- USS Yellowstone (runabout; existed in an alternate timeline)
- Delta Flyer (shuttlecraft)
- In production of Star Trek: The Original Series, Star Trek: Phase II, and Star Trek: The Motion Picture, several USS Enterprise prototypes were built.
- In production of Star Trek III: The Search for Spock, several USS Excelsior prototypes were built.
- In production of Star Trek: Voyager, a USS Voyager prototype mock-up model was built.