Improved Semi-Empirical Method for Power-On Base-Drag Prediction

Abstract

Improved methods for base pressure prediction under base bleed and rocket motor-on conditions have been deployed. The base bleed method makes several refinements to the method developed by Danberg at the Army Research Laboratory in Aberdeen, Maryland. The improved rocket motoron, base pressure prediction improves upon the method developed at the Army Missile Command in Huntsville, Alabama by Brazzel and some of his colleagues. The major refinement to the base bleed method of Danburg was to estimate the power-off value of base pressure empirically based on an extensive data base, as opposed to using computational fluid dynamics codes to predict this term. The major modifications to the power-on base pressure prediction method of Brazzel was to extend its range of applicability to high values of thrust coefficient, to Mach numbers less than 1.5, and to different afterbody shapes. In comparing the improved methods for power-on base drag prediction to experiment, it was seen that both methods gave reasonable agreement to most experimental data bases. However, more validation is needed, particularly for the combined effects of angle of attack, fins, and power-on conditions. Nomenclature