Effects of Boattailing and Nozzle Extension on the Thrust-minus-drag of a Multiple-jet Configuration

The investigation was conducted at Mach numbers from 0.60 to 1.40 and jet total-pressure ratios from 3 to 20. Three different boattails were tested: an 8-degree conical afterbody, a 16degree circular-arc afterbody, and a third afterbody having a linear area variation with length. A cylindrical afterbody also was tested for comparison purposes. Extending from these bodies were four circular jet nozzles with a design Mach number of 2.5 which were spaced symmetrically about the body center line. The 8-degree conical afterbody provided the highest net thrust efficiency factors when the nozzle exits were at the optimum longitudinal location. The other afterbodies in order of decreasing performance were the 16-degree circular-arc, the straight-linearea-distribution, and the cylindrical. (Author).