Comparison of exhaust duct designs in launch pads for reduction of rocket jet noise

Abstract

An exhaust duct is commonly installed in a launch pad to reduce the intense noise generated by the rocket exhaust jet at liftoff. In this paper, we investigate the effects of varying the length and shape of the exhaust duct by comparing the noise reduction performance of several different designs. The sub-scale exhaust ducts tested are variations of the original design by Tsutsumi et al. [AIAA Paper 2015-1007], colloquially known as “Seiji’s dog house,” and experiments are performed using cold jets of Mach 1.8 and 3.1, respectively. Linear and semi-circular microphone arrays are employed near the nozzle and at a radial distance of 100 nozzle diameters from the center of the duct outlet. A design guideline as to the length and the outlet shape of the exhaust duct, leading to the best noise reduction performance, is discussed. [This work was conducted at High-Speed Vehicle Research Center of KAIST with the support of the Defense Acquisition Program Administration and the Agency for Defense Development under Contract UD170018CD.]