> if you've colonized say 20 stars This is the sticking point for me. The rocket equation, energy being quadratic with velocity, and the impossibility of perf

> if you've colonized say 20 stars This is the sticking point for me. The rocket equation, energy being quadratic with velocity, and the impossibility of perfect efficiency (and, possibly, limits on material properties) constrain speeds. That means it takes a long time to get between stars. A long time. Which means if you venture between stars successfully, you're adapted for life in interstellar space. If that's the case, why would you go down the gravity well? There are lots of asteroids and comets to use in Oort clouds and between stars, and those down-well enviroments are hostile.