NASA's Mariner 1, intended to conduct the first American planetary flyby of Venus, launched from Cape Canaveral's Launch Complex 12 on July 22, 1962. The spacecraft and its Atlas-Agena rocket initially performed normally, but the booster began fishtailing after a brief loss of ground guidance lock. As the rocket veered downward and left toward Atlantic shipping lanes, a range safety officer ordered its destruction at 9:26:16 a.m., six seconds before Agena separation. The loss cost NASA $18.5 million, roughly $196.9 million in 2026 dollars.
A five-day investigation by JPL engineers identified both a guidance-computer logic error and a hardware failure. A required overline in the mathematical expression for a smoothed rate-of-change value had been omitted when a technician entered the handwritten equations into the Burroughs ground computer. When the Atlas rate beacon malfunctioned and guidance lock was restored, the flawed program interpreted the data as erratic and issued destructive steering corrections. The underlying Mod III-G guidance system was already unreliable and was redesigned in 1963. The incident drove stricter software debugging and fault-tolerance procedures at NASA, helping establish software engineering practices; Mariner 2 launched successfully on August 27, 1962, and returned Venus data on December 14.
