"Megaprojects of the future."
A space elevator. A moon base. Space solar farms. An underwater city.
For the space elevator one, he fails to mention the problem of space junk. If you put a satellite up in space, it orbits at a particular altitude and only has to worry about space junk at that altitude. But a space elevator has to worry about space junk at every altitude from the ground to geosynchronous orbit. Because of this, dodging space junk is a critical requirement of any space elevator that gets built.
So it's not just a matter of having a strong enough material. It's also a matter of making intelligent space-junk-dodging systems.
