It's been 97 years since a nuclear apocalypse killed everyone on earth, leaving the planet simmering in radiation. Fortunately, there were survivors. 12 nations had operational space stations at the time of the bombs. There is now only the Ark, one station forged from the many.
We're told the earth needs another 100 years to become survivable again, four more space-locked generations, and man can go home, back to the ground.
The ground. That's the dream, the reality however is much different.