Space Opera; Hard Sci Fi on my genre tree starts with Traveller. I've never played Traveller, but I have Gurps, and Hero Games sourcebooks, and would love to play some cliched sci fi tropes from "Behind the Claw"!
I would try to plunge in hoping to achieve an arena death match, star ship combat, fearsome space marine assaults, interstellar espionage, corporate sponsored wars, alien first contact, and lost civilizations. These type of grand adventures should be made available to your players as their PC's take shape preparing for their first adventure.
2.3 Space Opera, Hard Sci Fi
2.3.1 Traveller Universe