The hundred years thing is actually a known time period when studying the full effects of something on the human body. See you need to study at least 5 generations that are subjected to the circumstances. The first generation will always skew the results since they are the first. but each successive generation yields more and more data and trends. I mean it can take as long as 40 years in a single individual to manifest cancer or other such conditions. Heck I've known people who've been smoking longer than I've been alive who still haven't shown it but they likely will.
Can you give me a source on this? I am unable to find this anywhere, but perhaps I am looking in the wrong place. But in any case, perhaps we need a century to fully understand all the nuances of the effect but we don't need to understand everything perfectly to create a workable model. We have fairly easily overcome the problems of permanent settlement in environments far more extreme than an earth like space habitat.
When anb environmental habitat goes bad on mars.. you do realize it will take some time to plan and organize a recovery mission right. Not to mention the actual mission and by that time you've lost considerable ground on figuring what happened.
Who ever said anything about a habitat on Mars? I specifically said colonizing other planets would be a bad idea. We start with earth orbiting habitats. Relatively easy to access if something went wrong. Why would we move outside of our own orbit until we have figured out space station habitats?
Sci-Fi paints lovely pictures but I've said it before... if want to know what it'd be like living on a space station... sign on with a nuclear submarine for a year and enjoy the ever cramped claustrophobic environments.
That is what a current space station is like. By necessity a permanent habitat would have to be very large just to effectively rotate to create the gravity like force. There is no reason to create a cramped environment when it already needs to be very large.
The only reason space stations are so cramped right now is because they are constructed on earth and getting the space station up there is incredibly costly. The high material cost necessitates small scale projects. Once we over come the high material cost there is no reason building massive space stations would be any sort of problem. And that high material cost will be overcome, but more on that later.
As for cruise ships. The reason I used cruise ships is because they actually are not unlike floating towns. and they can spend weeks to months at a time out... so here's the thing. Many of the problems come with the simple fact that when you have large numbers of people in such situations the logistics and realities begin to scale in ways you can't imagine.
Once again, this is assuming extremely small space habitats. A cruise ship is only like a space station if you design the space station that way.
And like I pointed out in the first place, cruse ships were not designed for permanent habitation. 4 months does not count as permanent habitation. The problem with cruse ships arise from the fact that they are not permanent habitations, nor are they especially well designed.
Just the spread of disease alone would be a taske and worse you'd be surprised what low-micro gravity does to microbes. It bloody super charges fungi, bacteria and viruses. They get stronger and deadlier. While at the same time our immune system actually gets weaker and more than a few drugs actually become less effective in low-micro gravity.
Just one of the reasons why we need the gravity like force! We already have a solution for this problem. This isn't going to be a micro gravity situation. That is not a problem.
As for the spread of disease, it will be no worse than the spread of disease in any city or, as a worst case scenario, aboard an aircraft carrier. And the military seems to have that one under control pretty well.
As for asteroid mining. Yeah we can't even get people to mars and back in safe fashion let alone the asteroid belt.
If your biggest reason we can't mine asteroids is because we can't get people to the asteroids you clearly don't understand asteroid mining. We don't need to get people to the asteroids. No one ever suggested doing that, it is a stupid plan. We bring the asteroids to us. The current model is to send a tiny drone to the asteroid belt that identifies useful asteroids. We then send another drone that attaches high efficiency rockets to those asteroids which slowly accelerate them towards Earth orbit. The second drone also identifies more useful asteroids for the second wave.
After a start up period we have a steady stream of materials heading towards earth ready to be processed in orbit into whatever we need, from oxygen to water to fuel to metal for building a larger space station. Humans never even have to leave earth orbit for this to work. The cost is estimated to be extremely low, significantly lower than obtaining the materials though traditional mining. In the future it will probably be cheaper to get iron from space than from the ground.
I don't mean to be rude, but you are thinking of space colonization all wrong. You are thinking of building habitats on Mars and sending people to the asteroid belt and finding habitable planets. You then list all the reasons those things would be hard. You never stop to think why those things are hard, solutions to those problems, and most importantly if we even need to do those things at all. You are focused on the problems, not the solutions.