As a retiree advancing in age, I sometimes remember things that didn't happen (just wait til you get here!) or don't remember important details.

I just watched four episodes of NASA documentaries on the Mercury/Gemini/Apollo manned flights, and the tempo of those missions, many I didn't recall, was breathtaking. They launched a big mission every three months or so, one time launched two within 14 days including a repair of the launch pad after a post-ignition abort.

Introduced major new tasks and equipment (space walks, moon landings, moon rover cars, Saturn 5 rockets, etc.) with minimal rehearsal. Flew eight Moon missions between 1969 and 1972 and cancelled three final Moon missions after acquiring the hardware and training the crews!

They did lose three astronauts to a training fire, but recovered three unharmed from behind the Moon on Apollo 13, after an inflight explosion and some heroic improvisation (The movie Apollo 13 is almost a documentary.).

Available on Netflix.