I'm writing a science fiction series (with elements of Lovecraftian horror) which is set on an alien world whose resident species has just begun making serious headway on manned space travel throughout their solar system. Shortly after the discovery of a treasure trove of nigh-godlike ancient technology, outside forces involved with the making of that technology send the sun into a two-century countdown which will inevitably end in a supernova. The next two hundred and twenty-nine years are basically a marathon run partaken by countless nations and organizations, most of them desperately working to exploit the tech to protect their world from the substantial changes its parent star is going through. An age of technological wonders, overshadowed by a grim sense of urgency. One of these projects, the one that's headed by the story's protagonists, is essentially a space-ark meant to house millions. Rather, it's the result of what happens when someone follows up on the idea that, instead of building a massive ship and somehow getting it into orbit, they could use the moon itself as a ship, riveting an FTL reactor to its now-gutted interior and building colonies expressly designed to withstand such a journey. Basically, someone said "Let's turn our moon into the Death Star, only instead of a death ray, let's give it a massive warp drive and the ability to sustain a hundred million people for god-knows-how-long until we reach the next system!" I'm aware that this fiction, and that in fiction, pretty much everything is possible - but I want this to feel believable. And a project spanning two centuries, the result of which is meant to be fired off at superluminal speeds while housing a nation's worth of people, should feel like a monumental effort rather than a Deus Ex Machina for a species facing extinction-by-supernova. The point is, what should I be sure to take into account to avoid giving my readers a sense of "this is just plain stupid"?