The $327 Million Math Mistake
NASA's Costliest Typo
In 1999, NASA's Mars Climate Orbiter — a $327 million spacecraft — disintegrated in the Martian atmosphere. The spacecraft's builders used imperial units (pound-seconds). NASA's navigation team expected metric (newton-seconds). The computers were speaking two different languages. The navigation team had raised alarms, but management did not act on them and skipped critical end-to-end testing.
What Happened
On 23 September 1999, NASA’s Mars Climate Orbiter — a $327 million spacecraft — fired its main engine to enter Mars orbit. Instead of sliding into a stable trajectory, it passed 170 kilometres closer to the surface than planned and disintegrated in the Martian atmosphere. The investigation revealed a staggering root cause: Lockheed Martin’s engineering team had used imperial units (pound-seconds) in their thrust calculations, while NASA’s navigation team had coded their software to expect metric units (newton-seconds). The mismatch meant the spacecraft was receiving incorrect trajectory corrections throughout its 286-day journey. The navigation team had noticed the drift and raised alarms, but management dismissed their concerns to stay on schedule.
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