A Starship engineer once described the moment Elon Musk explained his most important manufacturing rule. It wasn't about speed. It wasn't about cost. It was about deletion. "The best part is no part. The best process is no process. If you're not occasionally adding things back, you're not deleting enough."
The rule is called "delete the requirement" and it is the single most counterintuitive principle in manufacturing. Every engineer is trained to fulfill requirements. Meet the specification. Build to the standard. The entire engineering education system is built around satisfying a set of constraints that someone else defined. Elon's first question when given a requirement is: "Who wrote this requirement? Make that person defend it."
He has said that the most common mistake smart engineers make is optimizing a thing that should not exist. They spend months making a component lighter, stronger, cheaper, and faster without asking whether the component is needed at all. The optimization is brilliant. The component is unnecessary. The brilliance was wasted.
At SpaceX and Tesla, every requirement is treated as guilty until proven innocent. If the person who wrote the requirement cannot explain why it exists and why removing it would cause a specific failure, the requirement is deleted. Not modified. Not relaxed. Deleted. If the deletion causes a problem, the requirement is added back. But the default is deletion, not compliance.
This produces a manufacturing environment that most traditional engineers find terrifying. Things are removed until something breaks. Then the thing that broke is added back. The end product contains only the components and processes that survived the deletion test. Everything else is gone.
The Starship rocket contains roughly 80 percent fewer parts than a traditional rocket of comparable size. The reduction is not from better design. It is from relentless deletion of parts that the traditional design assumed were necessary and that Elon's team proved were not.
The man who builds rockets and cars does not ask "how can we make this better?" He asks "does this need to exist?" The question is more powerful than the optimization because it eliminates entire categories of work that optimization can only improve. The best part is no part. The best process is no process. The man who deleted his way to Mars.