Star Trek: 10 Secrets Of The USS Excelsior

The USS Excelsior underwent minor modifications between her appearances in Star Trek III: The Search for Spock and Star Trek VI: The Undiscovered Country (for the record she also appeared unchanged in the background of Spacedock in The Voyage Home and The Final Frontier). These modifications included a redesigned bridge module, which ILM's model shop felt was too large in The Search for Spock, and minor changes to the top of the primary hull and back of the engineering section.

The Excelsior's registry number was also changed from NX-2000 in The Search For Spock to NCC-2000 in The Undiscovered Country, signifying the ship's transition from "The Great Experiment" to just another ship in the fleet.

In fact, the Excelsior was actually the first ship in the Star Trek franchise to be given the "NX" designation, a prefix which would go on to be used in other "experimental" starships like Star Trek: Deep Space Nine's USS Defiant (NX-74205) and Star Trek: Enterprise's NX-class Enterprise (NX-01).

What do NCC and NX actually stand for?

Well, despite the obvious connection between the "X" in NX and the word "experimental", Star Trek canon has yet to actually explain its registry numbers. According to original Star Trek: The Original Series production designer Matt Jefferies:

Since the 1920's, N has indicated the United States in Navy terms, and C means "commercial" vessel. I added an extra C just for fun.