Doesn't matter. If you take the conservative assumptions that go into manufacturing, say, a car and apply those to a rocket, you'll get something that won't eve

Doesn't matter. If you take the conservative assumptions that go into manufacturing, say, a car and apply those to a rocket, you'll get something that won't even lift off the ground, much less make orbit. Any rocket HAS to be very close to the limits of what materials used allow, and not the +50% margin of error you routinely seen in other fields. What you say about SpaceX is true, but only relative to the rocket industry as a whole. E.g. SpaceX uses cheap, available materials and simple designs over exotic composites and complex mechanisms. But they still operate close to the margins, as they have to in order to have any payload capacity at all. In fact, the move to steel probably reduced their mass margins even further. EDIT: Actually maybe I shouldn't have used a car as an example: https://www.youtube.com/watch?v=pJdrlWR-yFM https://www.youtube.com/watch?v=pJdrlWR-yFM