In "The Omega Directive", Captain Janeway gravely expresses the end of spacefaring civilizations as they know it should Omega destroy subspace, making warp drive impossible. It's one of my favorite scenes from Voyager, and one of the most thought compelling. What if warp drive were rendered useless across the quadrants? I'm sure there'd be a mass effort into developing alternative faster-than-light propulsion systems like quantum slipstream, but if all those starships from the Federation and beyond were suddenly stranded, what new cultures would develop from them? Even at full impulse it would take four years to reach the nearest star, so crews in deep space would basically all be like poor Janeway's crew plodding home at multi-generational speed. Do you think sleeper ships would come back into fashion? And if subspace were truly destroyed, how can communications work long distance? It's going to be a long, lonely road home, I'm afraid.