Accuracy analysis of the space shuttle solid rocket motor profile measuring device

The Profile Measuring Device (PMD) was developed at the George C. Marshall Space Flight Center following the loss of the Space Shuttle Challenger. It is a rotating gauge used to measure the absolute diameters of mating features of redesigned Solid Rocket Motor field joints. Diameter tolerance of these features are typically + or - 0.005 inches and it is required that the PMD absolute measurement uncertainty be within this tolerance. In this analysis, the absolute accuracy of these measurements were found to be + or - 0.00375 inches, worst case, with a potential accuracy of + or - 0.0021 inches achievable by improved temperature control.