I'm unclear on the point of why having a rocket blow up when you're being slow and careful is more of a setback than having one blow up when you aren't.
If instead you try to work out everything in painstaking detail, build a small number of prototypes that your calculations assure you should work, and one blow sup, you learn that...your calculations are wrong.
Imagine developing software with no CI tests, where you only get to run one full system test every couple of months. Slow and careful means avoiding lots and lots of early learning opportunities.