I originally posted this on the Aboslute Write forum, but I think it’s worth preserving for posterity. So here it is again:
One of the things that bugs me the most about modern SF stories are starships which have hundreds or thousands of crew members with very ill-defined roles. I can accept it in older SF written when computers were less powerful but I have a hard time suspending disbelief when confronted with a culture that can fly around the galaxy faster than light, yet can’t automate away most of those jobs.
In the Navy one reason you have lots of people on ships for damage control; if someone shoots a big hole in the hull you want a lot of bodies to plug it up before the ship sinks. In space, if someone shoots a big hole in the hull you either seal off that section of the ship or you’ll probably be dead in a few minutes. More likely, if you have a sufficiently advanced technology level, if it’s small enough to survive you seal it off and wait for the automatic systems to repair it for you.
This is particularly true if you have AIs, because you can probably fit a lot more AI systems into a ship than human crew. If the AI is good enough, you can eliminate the entire crew and the ship can fly itself.
Shift work may be necessary on a military ship, but probably not civilian. Anything urgent enough that you can’t wake up to fix it is probably urgent enough that you’re all going to die anyway. NASA tried shift operations on the Apollo missions, but soon decided that the whole crew should sleep and they’d wake someone if they had to deal with a problem. I believe shuttle crews did the same.
I have five crew members on the freighter in my SF novels and I’m not still quite sure what they all do; I keep removing someone because I can’t think of a good use for them in the crew, then bringing them back because I need them for the story. Which kind of works, one of them just gets very defensive if anyone asks him what he actually does.