The ELI5:

1. Big rock from sky hit Earth.
2. Earth get hot, then super dusty for long, long time. Dusty Earth block light from sun.
3. Plants die. Veggy Dinos no longer have lunch. They die.
4. Meaty Dinos no longer able to lunch on Veggy Dinos. They die.
5. Only tiny flying Dinos survive. Tiny flying Dinos become Birds.

The end.

IMO, we'd need robotic/AI companions to oversee the mission, and fertilize embryos/raise us once we get there. Either that, or we develop some form of stasis technology.

Can't really see any other way to make a journey that takes hundreds or thousands of years.

Agree.

Seeing Kelly Reilly in tight fitting clothing is a close second.