"But rocket science is arguably simpler than weight loss, in the sense that it involves less unpredictability and variation. We control how rockets are made, and they don’t change their material composition over time."

The composition of rockets do change over time. Small fractures, corrosion, wear-and-tear from reuse, and manufacturing defects can have catastrophic consequences. The exposure of O-rings to extreme cold, leading to the Challenger disaster, is one example.