Production sketches and final scale drawing by Matt Jeffries, 1965-1966
The Enterprise went through multiple iterations before production started, with Jeffries spending several weeks coming up with ideas that just weren’t hitting any of the notes he wanted. Finally, he had an epiphany — he would use his membership in the Aviation Space Writers’ Association to get materials from NASA, Northrop, Douglas and other companies that had designed spaceships.
"I pinned all that stuff up on one wall and said ‘This is what I will not do.’ The negative/positive approach," he said in an interview for The Star Trek Sketchbook.
He continued: “So I worked on it for a while, and a couple of weeks later Herb and Gene came in. They liked a bit of this and a bit of that, and I worked on those bits. And then I came up with something I really liked, so I preloaded it — used lots of color and put it in a prominent place that made it kind of stand out. And that worked! It looked better than the other sketches and Gene said ‘That one looks good!’ They — and Bobby Justman, too, when he came aboard later — were a dream to work with.”
Jeffries also relates how he came up with the NCC designation for the ship: “Since the 1920s, N has indicated the United States in Navy terms and C means ‘commercial’ vessel. I added an extra C just for fun. Interestingly, Russian’s designation is CCC so the N and the C together made it kind of international. After that, I had to pick some numbers. They had to be easily identifiable from a distance so that elemented 3, 8, 6 and 4 — none of which is that clear from a distance. That didn’t leave much! So 1701 was as good a choice as any. The reason we gave for the choice afterwards was that the Enterprise was the 17th major design of the federation and the first in the series! 17-01!”
I didn’t know that last fact! Later on, -00 became canon for indicating the first in a series…