My advice would be to get a degree, because it will open up some doors and put you farther up in line on others.
You want at least a B.S., but an Engineering degree would be better for some fields. I recommend a degree which qualifies as Shift Technical Advisor (STA): in summary you must have 2 calculus classes and 2 calculus-based physics classes or you aren't eligible.
Thomas Edison and Excelsior have programs that can be finished quickly, but you can probably get a more traditional degree.
B.S. is better than A.S., and A.S. is better than "I have the necessary credits but not an actual degree, please accept the equivalence."
(Test out as much as possible for the credits, the Navy provides good opportunities.)