I was running a campaign with FASA's Star Trek RPG and went about creating a complete crew listing for a ship similar to the TOS-style Enterprise, the U.S.S. El Dorado.

The problem was with assigning enlisted and non-commisioned ranks to crew-members; I instead had only a handful of cadet/midshipman yeomen aboard, the rest being officers from Ensign on up. FASA dumped a bunch of ranks into their sourcebook, and failed to explain where they exist.

So here is what I'm working from, out of FASA's 2nd Edition Cadet Orientation Sourcebook:

Elsewhere, the game mentions that smaller ships, manned with junior officers, are captained by ranks as low as Lieutanant, j.g. So I figure, _that's_ where the enlisted and non-com's go.