The contrast with modern software development is striking. Today we often rely on fast iteration and patching problems in production. Spacecraft software is the opposite
That has lead to some of the best rockets ever developed, and the largest satellite constellation by far. But part of the secret sauce is creating situations where you can take risks. Traditionally anything space-related deals in one-offs or tiny production volumes, so any risk is expensive. A lot of SpaceX's strategy is about changing this, whether that's by testing in flight phases the customer doesn't care about, being their own best customer to have lower-risk flights, or building constellations so big that certain failure scenarios aren't a big issue (while other scenarios still have to be treated as high-risk high-impact)
I would love to update myself if anyone has a good source.
For better or worse, it's hard to argue with results.
change the fundamental nature of the propulsion, or a step change in the technology, and it may be more effective to go with an engineered approach.
'engineered approach' --> before the item is built, a very good idea of how it is going to work has been determined. using math and science.