Design and CFD Analysis of Conical Nozzle for 2.75 Inch Rocket System

The 2.75 Inch Rocket System is a multi-service system consisting of launchers, warheads, and rocket motors. The air vehicle is a warhead and rocket motor combination that flies a free flight ballistic trajectory to the target. While the 2.75-Inch Rocket System has been modified over time to improve the performance, the system still experiences problems hitting a point target resulting in a high number of rockets needed to perform a mission. This problem is due to both low precision (wide impact distribution) and low system accuracy. Precision is affected by thrust misalignment, downwash and crosswinds whereas accuracy is affected by the launch system (aircraft and launcher) and the launch environment (air density). Both precision and accuracy need to be improved to increase the ability of the 2.75-Inch Rocket System to hit targets. The Naval Surface Weapons Center, Indian Head (NSWC-IHD) and General Dynamics Armament Systems (GDAS) are jointly developing a high-torque nozzle to improve the rocket precision. The current nozzle produces 3 ft-lbf of torque. The high-torque nozzle is designed to provide more than 10 ft-lbf of torque and significantly improves rocket precision by averaging out the thrust misalignment. The nozzle torque will shut-off at rocket exit from the launcher to limit the rocket spin rate below its natural bending frequency. A separate effort will modify the large pop-out fins to reduce the downwash effect from the helicopter. The program is currently in the design phase.