| While the aftbody nozzle flowfield can be analyzed with computer-intensive computational fluid dynamic codes, this approach is not suitable for use in conceptual vehicle studies. In order to accomplish any complete vehicle optimization at the conceptual design level, changes in performance due to the nozzle design must be available quickly. To make this task even more challenging, performance changes need to be assessed over a broad range of flight conditions, instead of just at a single point.; A new approach has been developed to enable accurate performance prediction and the optimization of the aftbody geometry. This approach involves generating response surface equations of the aftbody pressure distributions. The response surface equations are generated from the results of a new two-dimensional, inviscid flow solver. Parameters that affect the pressure distribution and serve as input variables to the response surface equations include the nozzle geometry, combustor-exit flow conditions, and the freestream flow properties. The results of this new approach have been incorporated into SCCREAM, a conceptual-level engine performance prediction tool.; As a demonstration of the usefulness and effectiveness of this technique, a sample design case was considered that involved an advanced, hypersonic launch vehicle concept. The vehicle performance, in terms of gross and dry weight, was assessed and compared for the three cases of a nozzle analysis using current industry practice, incorporating the new aftbody nozzle thrust predictions, and finally with the new aftbody thrust and lift predictions. |
