Wright Brothers to Yuri Gargarin was just over 50 years. Every decade until the 60s there were major breakthroughs with flight, from passenger planes, jets, supersonic, rockets, orbits and moon landings.
But in the last 40 years, we've regressed in terms of transport technology. Here in Europe, we're told 'rail is the future', an 1830s invention.
The 1970s had some bold robotic missions to the planets too: Pioneer, Voyager and Viking. This current decade looks paltry by comparison, with a lot of missions cancelled or 'descoped'.
30 years of tax cuts doesn't help. Since the shift to the political right in early 1980s, western governments are perpetually broke.
Also, we've hit a wall re: new propulsion. It was looking great when we rapidly went from sail to steam to internal combustion engine to rocket, but a new power power source is long overdue. Scramjets? Fusion? Antimatter? All too hard, either with the theory or the engineering. Maybe all the easy problems in science have been solved and it's going to take longer than we thought to get to the next 'order of magnitude' step in progress. Instead of an acceleration in major breakthroughs in transport technology, we're experiencing an deceleration.
Isaac Asimov envisioned a future in his Robot series where humans don't travel anywhere, but the world comes to them via VR 3D holographic screens. After all, IT communications has shot ahead in the same 40 years that transport has stagnated.
not long to go now...