“Oh crap! The Astrophage in the fuel bay! It’s exposed to space! That means it can see Adrian! My fuel is migrating to Adrian to breed!” “Bad bad bad!” That’s where the thrust is from. Trillions and trillions of horny little Astrophages, all ready to breed. And then, all at once, they see Adrian. Not just a source of carbon dioxide, but their ancestral homeland. The planet they evolved over billions of years to seek out.
