The Final Frontier

"Space... The final frontier..."

This is the "traditional" setting for Science Fiction, though it's not the only one by a long-shot.

Space is this huge vast bit of real estate just outside of Earth which is full of amazing and different things from the things we see here. These different things tend to take the form of normal 21st century humans wearing funny hats and negative space wedgies.

Basically, space is just like Earth, but with a different color scheme. Our heroes have a Cool Ship with which they fly around in it, going to various places where they can have adventures.

Space is usually coupled with The Future, but not always. The Future is a good timeframe for such stories because you need a lot of Applied Phlebotinum to make space travel really useful. For one thing, you need to overcome the pesky fact that with our current technology it would take slightly longer than forever to get anywhere even remotely interesting. But there are ways around this. You can be set on a moon colony or space station just Twenty Minutes Into the Future (as in Space Island One and Mystery Science Theater 3000), or the series could feature Earthlings among aliens (as in The Hitchhiker's Guide to the Galaxy or Green Lantern comics), or the technology could exist but be hidden by a Masquerade (as in Stargate SG-1).

Or aliens can give you the necessary phlebotinum. Thanks to Imported Alien Phlebotinum, Stargate SG-1 and Stargate Atlantis travel into The Final Frontier in a contemporary setting. On Farscape, John Crichton fell into a Negative Space Wedgie and ended up on an alien ship. In fact, this sort of thing may be the most interesting approach, since it minimizes the social and cultural disconnect between the viewer and the heroes. You also get the interplay of contemporary technology with space-age Applied Phlebotinum, and get to see how our heroes can MacGyver our own meager technology to solve problems that we're only used to seeing overcome via Techno Babble.

See also Tropes in Space, especially Space Western.