With advanced technology, we can modify humans to more easily survive in space. With sufficiently advanced technology, we can just upload them into robot bodies. That will make space missions as cheap as they are now, and without the risk. Because instead of sending up bags of meat that have to be protected from vacuum, radiation, freezing, boiling and dehydration, we can send up AIs or uploaded humans running on rad-hardened processors.
It goes back to the discussions about terra-forming. Is it better to adapt an entire planet (which is big, by the way) to human needs, or is it better to adapt humans to just live in that environment as-is?
Oh, and this sufficiently advanced technology gives you some other side benefits, including practical immortality, so that is worth pursuing by itself.
While I agree that 3 is the most optimal solution in the sense that "all these other problems are solved given 3", we still don't have a firm time frame on it. It could be 1 year, it could be 50 years. (I wouldn't put it at 100 or above personally, barring global catastrophe.) So we do things in parallel and hedge our bets. Could we get a self-sustaining colony on the Moon (or Mars, or somewhere else) within 50 years if we tried? I think we could. And that instantly protects modern humanity from many existential threats while we continue to work on problem #3.
Time frame is always a tough one. Let's try to bracket it with what we know, and be clear about the goal.
First, if we're talking about running an uploaded human-equivalent AI, we've got the processor power for that now, but it takes up a large server room. So I'd say we need to shrink stuff by at least 2 orders of magnitude to launch that into space. With corresponding gains in efficiency. So for that I think we're looking at 10 years at current rates of progress. Tack on another 5 for radiation hardening, because that estimate was based on commercial-grade hardware, which is almost as fragile as meat.
After you have that, it is a small matter of programming :-)
With advanced technology, we can modify humans to more easily survive in space. With sufficiently advanced technology, we can just upload them into robot bodies. That will make space missions as cheap as they are now, and without the risk. Because instead of sending up bags of meat that have to be protected from vacuum, radiation, freezing, boiling and dehydration, we can send up AIs or uploaded humans running on rad-hardened processors.
It goes back to the discussions about terra-forming. Is it better to adapt an entire planet (which is big, by the way) to human needs, or is it better to adapt humans to just live in that environment as-is?
Oh, and this sufficiently advanced technology gives you some other side benefits, including practical immortality, so that is worth pursuing by itself.