Unless you're going to just plant a flag and bugger
off, you're going to have to set up colonies. The earliest of
space enthusiasts realised this. The trouble is, and it is one
that still plagues colony advocates today, is the question of what do
you do when you actually get to another planet. When Columbus,
that oft cited parallel, discovered the New World, he found lands lush
with life, fresh air, water and all the good things of life.
When spaceships touch down anywhere in the Solar System, they
find inhospitable rocks.
So, space colonies have a depressing tendency to be
self-sufficient affairs that require nothing from the planet they are
on except raw materials, which begs the question of why go in the
first place. If you can scrape a bare living off of solid rock,
why not set up your colony in Death Valley or the Gobi Desert and be
done with it?