To me, it has always meant "performed the task that was named." For example, nominal performance for lift-off means that the rocket lifter off the launch pad. I

To me, it has always meant "performed the task that was named." For example, nominal performance for lift-off means that the rocket lifter off the launch pad. If it exploded two feet after lift-off, it's still a nominal lift-off. The sudden and unexpected vehicle disassembly following lift-off is a separate issue that would be dealt with as such. That has always been my understanding of "nominal performance" anyway.