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During the Apollo missions, an on-board computer and large computers on Earth performed the critical guidance and navigation calculations necessary for a successful journey. In addition, crews carried a slide rule for more routine calculations. NASA chose a 5-inch, metal rule, model "N600-ES," manufactured by the Pickett Company for their use. It was a model that was popular among engineers, scientists and students at the time. No modifications were needed for use in space.
This rule was used by the crew of Apollo 13, in April 1970.
