Kerbal Space Program is my favorite game right now (other than Magic: The Gathering, which is in a whole other category) and it's also the game I play while listening to the best show (3 hours is a good limit to a gaming session). It's a simulator of running a space program, you design all the ships, then pilot them. The astronauts are very cute little green men. Playing this game will accidentally make you an expert on orbital mechanics.