Great setup.
I went ahead and read part II (left a commnent there too).
Great story. Truthful to the genre. Excelent plot, nicely wrapped up in part II.
Every time I think about end of the world scenarios and a group of "pilgrims" surviving a space exploration to rebuild humanity, I think of the first settlers from the history we know and how they face hostility and survived against all odds.
If seems inminent that we will put an end to our planet, either by a total war or a natural disaster, probably induced by human actions.
Your story provides the cataclysmic scenario, but also the hope in a far away future.