Prototype was 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" prefix, and which were typically the first vessels in their class. (Star Trek III: The Search for Spock; DS9: "The Search, Part I"; VOY: "Non Sequitur", "Message in a Bottle") Once certified for operational status, however, these prototype vessels usually reverted to a more standard NCC prefix. (Star Trek VI: The Undiscovered Country; DS9: "Tears of the Prophets"; Star Trek Nemesis)
- USS Bradbury
- USS Dauntless (actually an alien vessel in disguise)
- USS Defiant
- Delta Flyer (shuttlecraft)
- USS Galaxy
- USS Prometheus
- USS Yellowstone (runabout; existed in an alternate timeline)
During production of Star Trek: The Original Series, Star Trek: Phase II, and Star Trek: The Motion Picture, several prototypes of the USS Enterprise, both in her original and refit configurations, were built.