Maybe someone else can explain why it made sense to focus on an orbiting refuge, right in the path of the Moon's fragments, rather than dig a bunch of underground cities that would have saved many times more people.
Midway through the first unit, I basically decided they should have dug tunnels ten miles long, one mile deep at bottom, lay tracks, and just go full steam carting rocks out while digging massive caverns. They could move entire hospitals, schools, factories, labs, etc. into these places, store tons of food and supplies, lay pipes to connect to underground water supplies, set up parks, farms, and animal preserves using artificial solar lighting. Makes so much more sense to me than this nutty space station idea. And with gravity, access to minerals, oxygen, etc.
I love space as much as the next geek, but if you want to save millions of humans, you've got to dig.