Diaspora is a hard sci-fi implementation of the Fate system. The website.
The tenets of the setting are:
- Each world was colonized by humans who originally came from Earth. In our case, no verifiable evidence about Earth has survived the intervening millennia.
- Science in Diaspora is the science of our world, with a few minor tweaks, and some theoretically possible technology that didn’t work out:
- Faster-than-light travel can only occur at the constrained location of slipstream end points
- The best way to propel ships through a vacuum is with reaction drives
- Anti-gravity doesn’t work
- Artificial intelligence is more artificial than intelligent
- The only place the rules of science get broken regularly is at the T4 technology point, which is also the point at which civilizations destabilize, becoming incomprehensible, collapsing, or disappearing altogether.
See page 55 of the book for more elaboration.
The main thrust of these is that human stories are interesting, and most things should be kept justifiable or at least plausible. However I don’t want this to constrain your imagination too much. Rather, I hope science’s limitations will inspire you and create interesting problems.