Like with the prescient Ladies' Home Journal predictions, much of what hasn't happened isn't so much that we couldn't do it, but that we can do it and find it uninteresting or inconvenient after all (like moon colonies: doable, just not much point given the cost involved vs benefits).
+1 to Willi there, moon colonies are not currently "doable". They will be once we have on-orbit re-fueling. That is because you have to have some way of transporting things you cannot get or make on the moon, too the moon.
The Apollo program, as impressive as it was, was never expected to be extendable to a colony effort. Rather first a space station was to be put in orbit, then on-orbit refueling, then space 'tugs', and then you could send up things that could land on the moon and ship additional building materials there.
That said, I found the hovercraft idea interesting since the benefit of hovercraft are completely negated by the inability to push against the surface for turning force and thus to re-capture forward energy into turning energy. This is a huge problem with lighter than air airships as well. Asimov should have known that.
It is irritating to hear claims that something can be done which has never been done. As evidenced by every project I've ever worked on, people have a very poor idea of how much work it takes to accomplish a task. There are very likely hurdles to building moon colonies that you have not considered.
There is a big difference between saying something is possible and saying something is easy. I don't think it is easy to build a moon colony. On the other hand, I do not see any scientific or engineering reason why it is not possible. We have already proven we can land on the moon and that we can build space colonies (i.e. ISS). Sure there are hurdles I have not considered, but that just makes it hard not impossible.
2. I bet we could figure it out. Again don't see any reason why it is not possible. Very little research has gone into that particular problem which I think is the main reason it has not been done.
It is irritating to hear claims that something can be done which has never been done.
Hardly irritating - that's my job, which I enjoy.
Sure, moon colonies would require enormous effort, staggering cost, and some new technology. The problem isn't the engineering challenge; we put people & equipment in a habitable box, and brought them back, using half-century-old technology. The problem is the cost far exceeds the payoff for anywhere close to the foreseeable future, and the scenery there is about as interesting as Death Valley (briefly compelling, but you wouldn't want to live there).
