Uncertainty analysis of rocket motor thrust measurements with correlated biases

The uncertainty analysis of a rocket motor thrust measurement and calibration system is presented. The thrust measurement system has 10 load cells with 5 in tension and 5 in compression, and the calibration system has 6 load cells. The elemental sources of load-cell random uncertainty considered are excitation voltage, amplifier stability and noise, and analog-to-digital conversion resolution. The elemental sources of load-cell systematic uncertainty (bias) considered are calibration, excitation voltage, nonlinearity, hysteresis, system alignment, and other mechanical sources such as friction. The calibration hierarchy and excitation systematic uncertainties are correlated since they have a common source. These correlation effects dominate the resulting thrust measurement uncertainties and form the focus of this study. The trust measurement uncertainty is up to three and a half times larger when correlation effects are considered relative to the case where correlation is neglected.