NASA lost its Mars Climate Orbiter in 1999 not because of a rocket failure, but because Lockheed Martin software reported thruster impulse in pound-force-seconds while NASA navigation software expected newton-seconds — a unit mismatch that sent the spacecraft dangerously deep into the Martian atmosphere and doomed the mission.

NASA lost its Mars Climate Orbiter in 1999 not because of a rocket failure, but because Lockheed Martin software reported thruster impulse in pound-force-seconds while NASA navigation software expected newton-seconds — a unit mismatch that sent the spacecraft dangerously deep into the Martian atmosphere and doomed the mission.

At 09:00:46 UTC on 23 September 1999, Mars Climate Orbiter began firing its main engine exactly as planned. Five minutes later, the spacecraft slipped behind Mars from Earth’s point of view. Its radio carrier vanished at 09:04:52, 49 seconds earlier than mission controllers expected. The silence itself was normal during an occultation. What was not normal was that, after the predicted 21-minute blackout, the signal never came back. JPL’s announc…