Indeed - Elliott waves come in mind too. As un-scientific as those ideas can be, not being expressed in any kind of mathematics, they seem to point at some possible reality in growth patterns. Notably, the fact that there's always a plunge after a first surge - where everybody think it's dead and where it starts a new uptrend - is something that makes me really curious.

Note that it's not just about people expectation either : humans actually went on the moon, they didn't just talk about it, and they didn't go any further in decades. So beside expectation, it doesn't seem far fetched to say there indeed was a plunge in achievements, at least if we consider distance traveled by humans (which should grow again when/if we go on Mars).