NACA-RM-L55L21

Abstract

INTRODUCTION <br>With the penetration of modern high-speed airplanes into supersonic flight regime, considerable interest is being directed toward the effects that propulsive jets have on external drag of nacelles and fuselage after bodies and on the base pressures around the jet exit. Data on base pressures and bottail drag (refs. 1 to 6) have shown that power-on drag coefficients may be considerably lower than the power-off drag coefficients. The magnitude of the difference in drag coefficients depends on the after body-geometry, nozzle-design, and jet-operating conditions. <br>In a much as there is no adequate analytical method available other than the semi empirical theories for calculating or predicting base pressures, the Langley Pilotless Aircraft Research Division is currently conducting flight tests to determine the effects of a sonic turbojet exhaust on body base pressure and total drag at transonic and supersonic speeds. The initial results, reported in reference 6, simulated a sonic turbojet exhaust at 35,000 feet altitude. The present investigation utilizes lower jet static-pressure ratios which correspond to flight at lower altitude. <br>Two research models with identical configuration, but with different jet static-pressure ratios, propelled with turbojet simulators (designed according to ref. 7) were flight-tested at Langley Pilotless Aircraft Research Station, Wallops Island, Va. Power-on data for model 1 covered a mach number range from 0.90 to 1.15 and Reynolds number range, based on body length, from 28.70 X 10⁶ to 35.00 X 10⁶, while that of model 2 covered a mach number range from 1.1 to 1.70 and Reynolds number range from 52.25 X 10⁶ to 59.00 X10⁶