OOC - How Do You Join a Sci-Fi Game?

There have been a lot of great looking sci-fi games as of late, such as The Rogue Dwarf, Ouroboros, Traverse, and Star Wars Rogue Moon, but try as I might, I can't think of a good character I could make for any of them.

My primary problem is that I don't know how to make a relevant character that I would actually be capable of writing. It seems to me that in most Sci-Fi games that take place on space ships, the relevant characters are extremely good at what they do, whether that be fixing things, fixing people, or shooting stuff. The problem here is that I obviously am not good at any of that stuff. I haven't ever been on a space ship or fixed any serious mechanical problems, I haven't been to med school, and I've never shot a gun. I also haven't read much Sci-Fi literature, so I'm not familiar with most of the tropes or conditions that affect space-faring people.

All that said, I doubt I'm alone here. So how do you guys manage to create a charcter that you are able to enjoy writing that is able to contribute to the story?