On 23 September 1999, a NASA orbiter arrived at Mars after nine months and 400 million miles. Nothing aboard it was broken. Everything worked. It fired its engine on schedule, behaved impeccably — and passed behind the planet forty-nine seconds early.
A program on the ground computed the spacecraft’s tiny thruster nudges in pounds of force. The navigation software that received those numbers assumed they were newtons. A pound is about four and a half newtons. So for nine months, every nudge was reported four and a half times too gentle.
The Magnanimous Doctor Warthan opens the file on the least glamorous failure in engineering: not the arithmetic, but the interface. Because people DID notice. Within a week of the data files working, someone saw the numbers were wrong. Three navigation methods disagreed all the way to Mars. The official finding is one of the coldest sentences in engineering: these discrepancies were not resolved.
Technical details drawn from the NASA Mars Climate Orbiter Mishap Investigation Board Phase I Report, 10 November 1999.
The Doctor’s voice and the Society’s imagery are synthesized.