So, complicated question, I'll try to give you info on the basics. (this is all from a Submarine background, surface ship's may be different. Also almost all Fast Attack, so may be slightly different on tridents)
First, go here:
http://www.nukeworker.com/forum/index.php/topic,17568.0.html then read this:
MM- Machinist's Mate: works on mechanical aspects of engineering plant, pumps, turbines, valve, seawater systems, Oil systems, etc.. Also operates almost all of the mechanical equipment in the engineroom
MM/ELT- Engineering Laboratory Technician: Works on all of the above plus responsible for chemistry control of Primary / Secondary plants and and radiation / contamination controls
EM-Electrician's Mate-responsible for all of the ship's electrical equipment, breakers, wiring, motor's oven's dishwasher, and laundry equipment. Also operates the ships electrical distribution system
ET-Electronic's Technician-Responsible for the reactor plant electronics and "computers", reactor safety equipment, and some of the reactor safety electrical equipment. Also operates the control rods and reactor operations.
Here are some links to some more info.
http://usmilitary.about.com/od/enlistedjob1/a/nf.htmhttp://usmilitary.about.com/od/enlistedjob1/a/mm.htmhttp://en.wikipedia.org/wiki/Machinist's_Matehttp://usmilitary.about.com/od/enlistedjob1/a/em.htmhttp://en.wikipedia.org/wiki/Electronics_Technicianthe above links list asvab scores for the different ratings.
So, as for his job, it will depend on what his aptitudes are. If he likes working on engines and taking things apart, be an MM. If he likes rewiring motors, seeing how electricity works, be an EM. If he likes messing with electronics, circuit boards, and soldering, be an ET. One thing to keep in mind, most Navy "technology" is 30-40 years old., at least in the nuclear world. Some of the really advanced stuff is 20 years old. Also, despite the descriptions above, including my own, most of what your son will be doing is nothing like that described.
Reality is something like this:
MM-getting filthy dirty cleaning lube oil purifiers, fixing oil leaks and cleaning out bilges. Occasionally get burned while working around hot steam piping, hours upon hours of boring endless watches. Months and years of learning, qualifying, advancing. Painfully long and boring evolutions and briefs. Nonstop cleaning and Field days (another name for cleaning)
ELT- same as above with added hours in sample sink and analyzing chemistry.
EM - same as above except instead of purifiers and bilges, you get to clean Motor - Generators and breakers
ET - same as above except endless trip and cals and reactor theory, along with panel watches.
Not to say that this is a bad life or a horrible life, it's kept me and mine fed and housed and clothed for 20 + years, and I've had some great opportunities. But, it's also a job with long hours, not enough pay for the work you do, and long separation from family and friends. But it's also a great starting point in life, and a springboard to other things, if that's how you make it. Like most things in life, it is what you make out of it. So if your son goes in with his eyes open, no illusions, and works hard, with a clear goal of where he's going, he should do just fine no matter what job he has. The most important thing is to work hard, and do what's right, no matter what.
Sorry for the dissertation. Hope this helps you and your son. Best of luck to him in his future endeavors.
