Flight-measured liftoff ignition overpressure - A correlation with subscale model tests

Analysis methods for the study of transient overpressures caused by engine ignition are considered. The initially developed analytical procedures are not adequate any longer in connection with the increasing complexity of payloads and launch vehicles. Developments leading to a more sophisticated analysis of the liftoff event are discussed, taking into account special instrumentation installed for two Titan launches. Data obtained from these flights, together with limited data from some other flights, provide the full-scale data base for an analysis. The model data used in the considered investigation are obtained from a 7.5% scale model test conducted at the Marshall Space Flight Center. It is found that the amplitude of the ignition overpressures with regard to compression and rarefaction pressure levels is well defined from the flight data.