need a hand with a plot element

Hi, Settlers,

Would you give me a hand with something I need in a story? First,
what would you call rather small communities, designed to hold several
generations of a family or several families, which are a cross between
space colonies and space ships insofar as they are intended to venture
into deep space over a long period of time?

And second, what would be a plausible economic mission of such a
ship/dwelling? In other words, what do we need in deep space that we
cannot get from objects in the near vicinity of earth?

Thank you,
Jan