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The Typo that Destroyed a Space Shuttle

Stashed in: FAIL, NASA, NASA to Me, You had ONE job., Freakonomics

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The Most Expensive Hyphen in History

On July 22, 1962, at 9:21 AM, Mariner I was launched to great fanfare. Less than five minutes later, the mission was “forcefully aborted,” $80 million went to waste, and the potentially historical flight came crashing to the ground -- all because of a tiny typo in mathematical code. On its website, NASA delineates what went wrong in the moments following the launch:

“The booster had performed satisfactorily until an unscheduled yaw-lift maneuver was detected by the range safety officer. Faulty application of the guidance commands made steering impossible and were directing the spacecraft towards a crash, possibly in the North Atlantic shipping lanes or in an inhabited area. [A range safety officer subsequently ordered its destructive abort.]”

Multiple theories emerged surrounding the reasons behind the craft’s failure, largely stemming from a bevy of reports produced in the aftermath (some official, and others merely speculation). But the most commonly cited explanation, directly from Mariner I’s Post-Flight Review Board, is that a lone “dropped hyphen or overbar” in the computer code instructions incited the flight’s demise.

Computer scientists have a name for this: The "Off by 1" error.

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