Prediction of Random Environments

A primary design consideration for any rocket boosted vehicle is the effect of acoustic and vibrational excitations on the vehicle structure and on delicate airborne equipment. These dynamic forcing functions display magnitudes in agreement with spatial patterns and are variant also with time and mission profile. This paper discusses fundamental techniques for the prediction of principal dynamic forcing functions on missiles and space vehicles. Predictions of rocket exhaust noise, boundary layer turbulance, and structural vibrations are presented, and various prediction techniques are examined and compared. Several methods of acoustic/vibration correlativity are utilized to provide comparative environmental vibration levels. The application of environmental vibration levels to the establishment of laboratory test levels is briefly reviewed. Data from numerous laboratory vibration tests are analyzed and summarized to define structural transmissibilities, Q, which are applicable to sine-random vibrational relationships.