You read a lot about colonizing the moon or Mars, but when you really think it through, unless you’re able to generate a gravity field, none of these places are conducive to human habitation without serious genetic modification. It’s Gravity stupid.
Once you leave standard Earth gravity you start losing bone mass. The moon has 1/6 Earth Standard and Mars 38%. You and your children are never going to be able to live back on Earth, it’s not about the muscles strength, it’s the lack of bone density. The truth is that any world that is 20% below ES will probably make things difficult or dangerous for the decedents to return to Earth. There are no other planets or moons in our solar system to safely raise future generations if we don’t develop a gravity field generator.
Sans artificial gravity fields, the only way around this is to generate your own mechanical gravity. For a space ship linear thrust can generate the G force to simulate gravity, for a space colony centrifugal force would be the only cheap option.
The ideal cheap colony site would be a 10×3 to 30×5 mile long asteroid, nickle iron, as much of a cylinder as you can make it. Hollow out the inside, strip mining a nickle iron asteroid from both ends should be cost effective in it’s own right. Seal the mining shaft, spin the asteroid to produce as close to 1G as possible and pump in air and water.
There are literally millions of such asteroids in the system, each a private haven. Just keep in mind a minimum width of 1200ft or the majority of your population will constantly suffer from motion sickness.
Sure you can build your O Neil colonies spheres or cylinders as well, but the cost of all that manufacturing.
Space colonization should always keep in mind, we’re only human and that means we have a small range of environments that we can thrive in without making significant changes in our physiology.
Keep It Simple Stupid works every time.
Most asteroid colonies will probably be a few miles long and maybe a half mile or so wide, covered in solar collectors, filled with various recycling devices, hydroponics and probably aqua culture. Lite manufacturing and repair facilities on par with neighborhood garages.
Over time as the initial Mining boom collapses most would probably fall in to niche agriculture. Like most farms most of the young will leave for bigger colonies, which is a good thing for those who remain as they grow or raise more surplus. You could go up the food chain to meat animals. Dairy farm?
Finding worlds that fit our Super Goldilocks zone to keep our species coherent will be a challenge, even if there are a 2 billions stars in our galaxy.
The creation of artificial gravity fields or planetary engineering are the only real options if we want to maintain the base line on a wide range of planets.
Then again evolution is about change. Who will we really be in a thousand years anyway?