Software Testing Blog

This month’s installment of ‘This Week In Testing‘ takes us waaaay back to 1962 when the Mariner I space probe, America’s first planetary flyby that was supposed to go to Venus, went completely off course and had to be immediately destroyed — a mere 293 seconds after launch.

The Cost? $18.2 million (in 1962!)

The Bug? Omission of a single overbar

The Mariner I was the first spacecraft of the NASA Mariner program that “launched a series of robotic interplanetary probes designed to investigate Mars, Venus and Mercury (Wikipedia).”

The bug that brought the mission to its speedy end was carried out by a programmer, who while transcribing a handwritten (in pencil no less) formula into code, missed one single overbar (or as it’s less-technically known: the hyphen).

NASA’s public account of the software glitch is written as follows:

The Mariner 1 Post Flight Review Board determined that the omission of a hyphen in coded computer instructions in the data-editing program allowed transmission of incorrect guidance signals to the spacecraft. During the periods the airborne beacon was inoperative the omission of the hyphen in the data-editing program caused the computer to incorrectly accept the sweep frequency of the ground receiver as it sought the vehicle beacon signal and combined this data with the tracking data sent to the remaining guidance computation. This caused the computer to swing automatically into a series of unnecessary course corrections with erroneous steering commands which finally threw the spacecraft off course.

Fortunately, the mission was successfully completed by Mariner 2 five months later, but it’s hard to ignore the significant costs brought about by a mere hyphen. Do you have any bug stories like this one? Has a missing bar (or something equivalent) ever led you to a messy debacle?