Elon Musk reflects on how difficult SpaceX's journey really was. "When we started SpaceX, we really had no idea how to make rockets." Falcon 1 failed three times before finally reaching orbit. Then came an even bigger challenge: landing and re-flying an orbital booster. Musk says many aerospace experts told him it wouldn't work—and even if it did, nobody would want to fly on a used rocket. But SpaceX kept going. Today, Falcon 9 boosters take off, land, and get recovered every few days. SpaceX also went on to build Falcon Heavy, once the world's most powerful operational rocket, and is now approaching its 700th Falcon flight. From blowing up rockets to routinely landing and reusing them. That's what years of iteration look like.