Experimental investigations on the strut controlled thrust vectoring of a supersonic nozzle

Abstract

The attitude control of a rocket engine using the control surfaces becomes cumbersome particularly in larger rockets with high payload. In such cases, a more effective means of producing forces for controlling the flight is the deflection of exhaust gases, referred to as the gas-dynamic steering or the thrust vector control. In this study, the effect of a strut on the exhaust gas deflection, deployed at the locations; 0.62 L, 0.72 L and 0.8 L in the divergent-portion of a Mach 1.84 nozzle at over-expanded, correctly-expanded and under-expanded states of the jet, has been experimentally investigated. The level of expansion at the nozzle exit is varied by changing the settling chamber pressures from 4 bar to 8 bar, in steps of 2 bar. Further, to study the effect of aspect ratio, the height of strut is varied as 1.5 mm, 2.5 mm and 3.5 mm. The strut of height 3.5 mm, deployed at x/L = 0.72, is found to be the most effective thrust vector control at overexpanded conditions; with a maximum jet deflection of about 3.6°, obtained at a settling chamber pressure of 4 bar. The Schlieren flow visualization images confirm the findings of wall static pressure data.