Standard Deviation of Launch Vehicle Vibration and Acoustic Environments

Statistical analyses are used for the development of the acoustic, vibration, and shock environments on launch vehicles. The standard deviation of these environments is critical for deriving accurate statistical extrema. However, often very little measured data exist in order to define the standard deviation. In many cases, the use of a typical standard deviation is better than the use of one derived from a few measurements. Extensive Space Shuttle Program and Expendable Launch Vehicle flight data are used in this paper to define a typical standard deviation for acoustics and random vibrations. The results suggest that, in the absence of sufficient data, 3 dB is a practical selection for the standard deviation of these environments. Further, the data are used to show that a standard deviation of 3 dB should be used for cases in which there are less than five data sets because there is not enough information to supersede the 3 dB estimate.