Base drag prediction on missile configurations

Abstract

New wind-tunnel data have been taken, and a new empirical model has been developed for predicting base drag on missile configurations. The new wind-tunnel data were taken at NASA Langley Research Center in the unitary wind tunnel at Mach numbers from 2.0 to 4.5, angles of attack to 16 deg, fin control deflections up to 20 deg, fin thickness-to-chord ratio of 0.05 to 0.15, and fin locations flush with the base to two chord lengths upstream of the base. The newly developed empirical model uses these data along with previous wind-tunnel data. It estimates base drag as a function of all the preceding variables along with boattail and power-on or power-off effects. In comparing the new empirical model to that used in the former aeroprediction code, the new model gives improved accuracy compared to wind-tunnel data. The new model also is more robust due to inclusion of additional variables. On the other hand, additional wind-tunnel data are needed to validate or modify the current empirical model in areas where data are not available.