Epic failures: 11 infamous software bugs

Celebrate 'Debugging Day' by remembering these monster problems from the past

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Mariner 1's five-minute flight

On July 22, 1962, the first spacecraft of NASA's Mariner program blasted off on a mission to fly by Venus. The booster did its job, taking the spacecraft from its Cape Canaveral launchpad, but after a few minutes, Mariner 1 began to yaw off course. The guidance system failed to correct the trajectory, and guidance commands failed to correct it manually.

As the rocket veered off toward North Atlantic shipping lanes, the range safety officer did the only thing he could do: blow the thing up. Four minutes and 55 seconds into the mission, the Mariner 1 exploded.

NASA was already suffering from Sputnik envy, and the Mariner 1 incident was another international embarrassment for the agency. The postmortem of this debacle revealed what NASA described as "improper operation of the Atlas airborne beacon equipment" -- though later it came out that the mistranscription of a single punctuation mark by an engineer caused the mission's fatal software error.

In his 1968 book The Promise of Space, Arthur C. Clarke described the mission as "wrecked by the most expensive hyphen in history."

That may not be strictly accurate. Although NASA did mention a hyphen in some of its reports of the incident, it appears that the agency was simplifying the story for a nontechnical audience.

A more widely accepted account is that the punctuation mark was a superscript bar over a radius symbol, handwritten in a notebook. In rocket science, the overbar signifies a smoothing function, so the formula should have calculated the smoothed value of the time derivative of a radius.

Without the smoothing function, even minor variations of speed would trigger the corrective boosters to kick in. The automobile driving equivalent would be to yank the steering wheel in the opposite direction of every obstacle in the driver's field of vision.

But few people know what an overbar is, and since it looks like a hyphen, that's how most people tell the story.

After the sidebar: Forty seconds of Ariane-5

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