Nozzle Flow Separation

During the sea-level ignition process of rocket motors, the nozzle is subjected to an overexpanded flow condition that can cause high side loads. Prediction of the symmetrical separation location is the first key step to a determination of the range of possible side-load magnitudes. The mechanisms responsible for causing the flow to separate from the nozzle wall are demonstrated, and the theory for a new solution of the separation location is presented. The model is also correlated with historical rocket data, a new approximate solution, and an empirical curve fit that has been in use for 35 years. (Author)