How about thinking of a nice official sounding term and running it through the linguistic rock-tumbler a few times. "Boatswain" becomes bo'sun, "starfarer" becomes starfer? Just at thought.
Maybe: Starseekers/Seekers - Those who undergo great voyages, "seeking something great among the stars". Mariners - An old term for sailors, but if you are going for something poetic then here you go.
I do wonder which way it will go. Though science fiction - which has a terrible track record as regards predictions - has traditionally pegged space armadas as a natural evolution of navel tradition, currently, as it stands, today, in this moment, right now (because someone is going to come along and mention shit from 50 - 60 years ago) the USAF is the military branch most closely cleaved to all things Cape Canaveral.
Well, every once in a while Science Fiction gets it right. We've been promised flying cars since the 50's and those are not coming to a driveway near you any time soon, but we did get communicators, and I daresay what we have is a step up from the clamshell monstrosity Kirk used.
I'd love to argue for Space Marines, but a) Where we gonna invade? and b) Yes, there are helicopter, Harrier, Osprey, and fighter pilots, but I think it would be best to leave the technical stuff to the technical boys (and girls) of the Navy and Air Force. Dibs on door gunner though.
Not to mention that a future where Martian Marine GySgt Bobbie Draper doesn't happen is a sad future indeed.
I want to believe that astronauts drink beer on the moon, but the glass of beer isn't reflected in his helmet. Why must you crush my dreams so cruelly?
https://www.popularmechanics.com/technology/a8813/why-dont-we-have-holodecks-15306311/ This article was written in 2013... I'm hoping we're a lot closer to getting our holodecks. I could use a speedo clad manservant to bring me drinks while I kill aliens. I'd also like to attempt to write a holo-novel.
At the moment Air Forces tend to be the most spacey but if you're wanting an organisation to man and operate large, complex vessels on long voyages in a 3D environment you probably want to use submariners rather than fighter pilots: it's going to be easier to teach Deeps to fly than to teach Crabfats how to run a ship's company and a nuclear reactor. God knows what the slang term would end up being (Spaceys? Like 'Space Cadets'?) but they'd probably stick with 'astronauts'- divided into 'ratings' and 'officers', naturally- as formal terminology. Hell, they might just stick with 'sailors' after all, depending on whether or not your fictional space-navy is a branch of a normal navy. Most people are going to call them by some sort of faintly derogatory nickname, though. Nobody ever nicknames anyone anything cool; it's always an insult.
The name of your "sailors" doesn't necessarily need to be unique. I would stay stick with something like OB1 is talking about. Your readers won't have to be pulled out of the story to figure out what your crew's name/title means and they can remain immersed in the world to focus on characters and story. If you're trying to come up with words for a specific title or rank for a particular function such as "commander," I think your best bet is picking something people won't have to think about too much. I think sometimes it's purposeless to use a made up name when a perfectly good name already exists. I recommend doing research. For instance, someone above brought up "jack-tar/tar." There are plenty of other terms. If you do the research, look into things that parallel what your crew is doing. If it's a salvage ship, look into things that have to do with salvage. Just a thought.