I think that's an incorrect way of looking at it. A small unforeseen factor is almost always going to be a negative factor, not an unforeseen benefit. Space is a hostile and unforgiving environment without an easy way to bring things back, fix stuff, and/or re-deploy. A small mistake on the engineering, planning and/or implementation is likely to sink the whole thing worse than the napkin math suggests is almost certain failure anyway. Similarly, there are few ways to "get it right" and many ways to fail.