Shock Vector Control of a Double Divergent Nozzle for Futuristic Space Vehicles

Double divergent nozzles (DDNs) have been explored in the recent years to enhance the launch capabilities of space vehicles. A DDN is touted to be beneficial for launch vehicles over a single divergent nozzle (SDN) because of its ability to mitigate the generation of side loads. In order to maintain stability under varying nozzle pressure ratios (NPRs) and control the attitude for such systems, thrust vectoring on a DDN becomes very important, which still remains an open area of research. Shock vector control (SVC) is the simplest of all fluidic thrust vectoring (FTV) techniques, which is used to deflect the nozzle's primary flow by the generation of a shock wave. The present study is conducted on the SVC of a two-dimensional (2D) planar DDN. Three different DDNs are considered by varying the base nozzle and the extension nozzle lengths for a fixed value of the inflection Mach number (IMN). It is observed that the SVC performance of a DDN depends on the location of the inflection point, indicating that it is the function of the lengths of the base nozzle and the extension nozzle. In the high NPR regime, the pitch thrust vector angles are the highest for the DDN configuration in which the base and the extension nozzles have equal lengths. At the highest tested NPR = 10, this DDN configuration achieves a pitch thrust vector angle which is approximately 50.46% higher than a reference SDN of similar nozzle area expansion ratio.