Give more information.
- who owns the ship? (government - like StarTrek, self appointed saviour of the universe - Andromeda, private enterprenuer - Firefly, fugitives - Farscape)
- what is the purpose of the ship? (combat, exploration, trade)
- how many crew is on board (the structure of 1000 men Enterprise from StarTrek and less than 10 of Firefly is greatly different in function)?
Also, do you strive for realism? Note that StarTrek is a complete nonsense in term of any kind of crew management realism (sending a well trained unique space pilot capabe of operating this huge ship to an away mission where he could die by one random bullet is insane; you have a specialized batallion of space marines for this)
If we talk about a big ship the crew would be probably something like this:
- bridge staff (navigators, pilots, commanders)
- engineering (runining the power source of the ship, maintenance, repairs)
- space combat & security (tactical - and it should not be just one person like a tactical officer, artillery/torpedoe operators)
- freight and fighters (pilots of smaller ships docked on the mothership; to carry cargo/people around and to fight and for reconeisance)
- ground combat (space marines)
- crew reponsible for the main task of the ship (could be scientists, some geologists that go on away missions)
- civilian support staff (cooks, barbers, medical, administration, quartermaster, paymaster, etc)
Who owns the ship? Faltering Earth government wanting to expand to new planets, but in a very Kirk/Picard'ish manner as Captain you would be pretty independent (With chance of annoying Earth in the process).
Purpose, primarily exploration and finding colonization sights but with capabilities to undertake the other two (Trade and combat). Ships could be customized for certain roles. I imagine you start off in something scout/corvette sized and can work your way up as you establish Earth's presence in the galaxy.
I imagine the crew to range from 2 to 40, no more than 100, more in the sense that I didn't want all this crew management to become to unbearable.
As for the realism aspect of away missions, nope ... because a large part of the appeal of this idea is that you get to explore planets and such in person. I would probably have it so you could send independent away teams down to do their own thing, but having the option to go yourself is big sell I think.