they are called CHIEFS in Star Trek. Same deal, different service. Star Trek followed Navy rates and ranks
That too. The writers seemed to think that only officers were on board, and that lowly ensigns would do the grunt work normally done by Chiefs and lowly petty officers. Somewhere there was a comment that Roddenberry believed all folks on the starship were officer material and therefore there were no enlisted personnel. Can't remember where or when I read that.
except we've heard the term "crewman" on several occasions... that seems to imply an enlisted rank analogous to seaman or airman.
Chief O'Brien is the only one that was a featured player, and they kept changing his rank pin 'cause they couldn't figure it out.
The ranks in Star Trek don't seem to be too formalized among enlisted personnel. We've seen Chief Petty Officers (like O'Brien), but anyone below that rank seems to simply be a "crewman." Slightly off-topic: Starfleet has been described as not being a military, but they sure do seem to have all the trappings: formal command structure, accountability to political authority, orders, ranks encompassing officers and enlisted personnel, uniforms, weapons (including weapons of mass destruction, launchable solely on the Captain's authority!), defensive obligations, etc.
Yeoman is a position, not a rank. The other branches call it adjutant. Basically they're a senior officer's administrative assistant.
The Air Force isn't part of the Navy. The Air Force STARTED as part of the Army, but it quickly became administered separately and was eventually made into it's own separate thing in 1947. The Navy does have a very sizable air component, with all the aircraft carriers and all. In fact, the US Navy's aviation branch is larger than most counties' entire air forces. But it's still a totally separate thing from the US Air Force. Now the US Marine Corps is an odd duck. It's technically a totally separate branch of the US Armed Forces, with it's own representative on the Joint Chiefs of Staff and everything, yet the USMC still answers to the Department of the Navy without being a part of the actual US Navy.
Like it's been said, from what we have seen in ST they are almost always naval ranks (Petty officers) and not Army / AF / Marine Corps (Non Commissioned Officers), though in The Undiscovered Country there was a Colonel West. SO maybe Starfleet has some sort of sergeants. Who knows? As for POs / NCOs, IIRC Roddenberry, in his pursuit of an ideal world, didnt want any enlisted ranks. Everyone was to be an officer and be oh so special. It wasn't really until partly through DS9 that TPTB got around to directly addressing the idea of senior enlisted personnel (O'Brien). Interestingly enough O'Brien's rank was described as Non-Com (short for Non Commissioned Officer) and never as a Petty Officer. Interesting real life side bar. IIRC at one point, eons ago, I'm talking about before any of us were born, the idea of calling all of the POs / NCOs the same thing was bandied about. The Navy said fine, we'll call them all petty officers. It looked that was gonna get passed by congress. Then the Army (Chief of Staff I guess) made the statement that none of its officers were petty, and kindly told everyone else to fuck off and invited the Navy to go back to fucking sheep on their deployments (well that was the general ida of their statement).
That Tom Cruise is a busy fella! it's hard being the world's best: 1. Bartender 2. Race Car Driver 3. Pilot 4. Double Naught Spy 5. Motivational Speaker (Magnolia, great movie BTW) 6. Kidnapper (Katie Holmes AND Nicole Kidman!) he's the The Fonze from Happy Days, on steroids!
BTW in answer to the original question, because ST has.....wait for it..... no time for Sergeants! BTW PLO (Permanent Latrine Orderly) is a sweet gig if you can get it.
Roddenberry seemed to want to get away from the idea as he got older, and had to be reminded that Starfleet started out as a military organization by one of the directors.