In 1999, NASA lost a $327 million spacecraft because one engineering team was working in metric units and another was working in imperial — and nobody noticed until the Mars Climate Orbiter was already vaporizing in the Martian atmosphere. We dig into how a single unconverted number, a chain of unchecked assumptions, and a very human reluctance to raise the alarm turned a triumph of space exploration into a very expensive lesson in communication. If last episode taught us that software can silently fail us here on Earth, this one proves the universe has zero tolerance for rounding errors.