That's a very reductive way of looking at it. They didn't blow up a rocket to find out a specific thing. The build the infrastructure, build production line, t

That's a very reductive way of looking at it. They didn't blow up a rocket to find out a specific thing. The build the infrastructure, build production line, train the team, prepare the rocket, launch the rocket and then attempted the two different parts of the rocket, only the combine them and refly them again to find out that in a specific case where the rocket does specific sequences of events certain assumptions they made in the design that were not obvious in simulation could lead to problems. Even more importantly the validated 1000s of other assumptions they made that turned out to be correct. > or handled with better tolerances This is the fundamental mistake in your thinking. It leads to an approach where on every layer of the design every engineering team introduces huge tolerances, just to be sure. This then leads to a system where any individual part has huge tolerances but the system as a whole is costly and performs badly. One of the first and most important design principles at SpaceX is to challenge requirements. Rather then just adding tolerances you do only what you think you will need. If you do not do to little at least some of the time, you haven't been aggressive enough. SpaceX probably made many design choices with very tight tolerances where a conservative engineer would have added them. Turns out 1 or 2 of them bit them in the ass, but with this test flight they likely validated that many others are fine. > I really don't get a sense that this "rapid iteration" approach is a good replacement for better engineering and more care. What evidence are you basing this assessment on? What large reusable rocket was build with the traditional approach? The only thing that is even remotely close (and it really isn't very close) is the Space Shuttle. The Space Shuttle was very expensive to develop, well above 10 billion $ and didn't achieve many of the goals it had. And it wasn't reusable, with the large external tank not being reusable and the solid rockets being not practically reusable. If NASA tried to build the Shuttle today, with modern requirements for safety, it would cost much more. Maybe it will end up being more expensive and fail as a project. But its very early to suggest that. The have developed arguable the best engine ever and have launched the most powerful rocket in history. Not bad so far I would argue.