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In page Wernher von Braun:
"Von Braun's early years at NASA included a failed "4 inch mission." On 21 November 1960 during which the first uncrewed Mercury-Redstone rocket, the rocket only rose up a mere 4 inches before settling back down onto the launch pad. The unfortunate and untimely failure of the rocket launch created a "nadir of morale in Project Mercury." The launch failure was later determined to be the result of a "power plug with one prong shorter than the other because a worker filed it to make it fit."[citation needed] Because of the difference in the length of one prong, the launch system detected the difference in the power disconnection as a "cut-off signal to the engine." The safety system in fact stopped the launch.[4]