Lots of great mods, including Create, Applied Energistics 2, & Thermal Dynamics, for a classic scifi feel.
It features a lot of intermingling technology mods to give the feel of a technologically advanced player, who can create an industry, a city, or an entire tech civilization. It encourages exploration to make the most of what the minecraft world offers, with new biomes and features integrating with the technology so that you can build whatever you want- with machinery or by hand, depending on what you want!
If you're looking for that crash-landed-on-an-alien-planet feeling, so that you can make your own mark and maybe even surpass the technological world you came from, this is the modpack for you.