"colonising other planets the engineering challenges are going to be a minor part"
But it's taken a long time to get to this stage.
The joker in the pack is what are the drivers for people wanting to go to (say) Mars?
The question that's been phrased is "If you're going to Mars for a 'better life', what is that 'better life'?"
And will most of the people for whom "Life on Mars" would be a better life be allowed to go?