Beyond Extremely Dangerous...

Going into the atmosphere at this point carries risks, but people shouldn't die too often. Going further out gets progressively more dangerous, as the distance to bailing out gets longer and some systems more systems would have to work, for longer, to get a vessel in trouble back to Earth and then land safely. The Moon hasn't happened in a while, but I'm not assured that another mission would meet safety and reliability standards for most people today. We haven't sent people further than that. Mars has weather that might not have been currently insurmountable, if not for the fact that we sometimes don't get satellites that far simply in the void, and then the aforementioned weather is made much more problematic by extreme lack of hospitality (food, unfrozen water, heat). Getting further out in the solar system is even more annoying and then I have to mention going beyond it. That would be interstellar space; with extremely little matter in it and light years to cross in order to find another star, leaving looks a lot like space launch did before aviation.

When we get into the issues of even more dangerous things, like intergalactic voids and black holes, it doesn't seem too fearful to say that maybe those things will sit merrily in theory while humanity concerns itself with the possible. That doesn't get us anywhere. We don't claim to know much about the universe. It may very well be that we'll find something(s) that would allow such travel that we've imagined, and been stumped by. Stations and self-sustaining colonies are interesting theories, but they still have to assume we have technologies we don't have now. I have a saying for this I made up just now: browsing for a future. Humanity is looking around at some things it might be able to pull off, then works on a few of them. In history, things we find weren't in the booklet. They don't ever seem to be in the damn booklet that is our imagination. That isn't entirely true, there are discoveries that have to do with where we want to go. Accidents and wonderfully epic failures usually aren't in the booklet. Thanks, Mr. Observation. Messing up our perfectly conceived universe. At least you make it a bit easier to find Ms. Reality. From step by step to a fell swoop/a few fell swoops, we may yet figure out the hazards of space, and travelling safely.