International Journal of Engineering Research ISSN:2319-6890 (online),2347-5013(print) Volume No.6, Issue No.2, pp :98-100 1 Feb. 2017 IJER@2017 Page 98 Design and Analysis of Motor Casing for an Aerospace Vehicle Chunchu Sravanthi 1 , Pratibha Dharmavarapu 2 ,Pooja Angolkar 3 Anurag Group of Instituions , Telangana, India sravanthimech@cvsr.ac.in ,pratibhamech@cvsr.ac.in, 21pooj@gmail.com Abstract : The aerospace vehicle like rocket motor casing is used for storage of fuel and it acts as a chamber for fuel consumption process. Nozzle is the main component of the rocket motor which converts the chemical energy into kinetic energy. For initial pressure build-up inside the chamber, the nozzle is closed with a nozzle blank. Head end and nozzle end grids are used in supporting the solid propellant grains in the casing.The motor is designed and structural analysis has been carried out using FE package and details are presented in this paper. The present investigation is aimed to study the following: Design of the rocket motor hardware for standing the MEOP of 110 Ski ,Structural analysis for getting the minimum available FOS ,Calculation of stress at weld zones and‘O’-ring dilation INTRODUCTION Rocket motor is a device which produces power to propel the object in a particular direction, with a certain speed. The rocket motors have wide applications in space shuttle and satellites. It will use solid, liquid, electrical propellants as a fuel for producing the power. It consists of different types of components like motor casing, nozzle end dome, head end dome, nozzle blank and head end grid, nozzle end grid, etc. DESIGN REQUIREMENT: Motor casing for aerospace vehicle has been designed with the following input data:  Average thrust at ambient = 1300 kg  Maximum expected operating pressure = 110Kg/cm 2  Motor duration = 0.35 Sec  Maximum diameter of the casing =159mm  Internal diameter of the casing = 154.7mm  Overall length (maximum motor length) = 383mm  Material = 15CDV6 Steel MECHANICAL PROPERTIES Ultimate Tensile Strength (UTS) → 100 Kg/mm 2 %Elongation → 8%max Hardness → 28 to 32 RC Density → 7.8 gm/cc Yield strength →95Kg/mm 2 Young’s modulus (E)→2.1X 10 6 Kg/mm 2 DESIGN OF ROCKET MOTOR COMPONENTS: IDENTIFICATION OF CRITICAL PARTS: In rocket motor all components are critical to ensure high reliability which are as follows.  Main Shell  Head End Dish  Nozzle End Dish  Graphite Insert  Nozzle Divergent  Head End Grid  Nozzle End grid  Nozzle Blank  Nozzle End Cap  Dish Retainer Ring 1. MAIN SHELL: For determination of tube thickness based on hoop stress ASME code section VIII is followed. t = (P*R)/(σ allow *η weid ) where t = thickness, in mm P = Maximum expected operating pressure = 110 kg/cm 2 R = radius of tube = 7.95cm η weid = 95% σ allow = (Ultimate tensile strength) / ( safety factor) = 10000/1.5 = 6666.66 t = 110*7.95/(6666.66*0.95) = 1.38 mm A seamless tube of outer diameter 159mm and inner diameter 154.7mm and a length of shell 177.5mm and a thickness of 2mm has been chosen for fabrication of casing. 2. HEAD END DISH SELECTION: A torispherical dish has been chosen for this design for the above advantages. The dished end has to accommodate head end grid and igniter holder. The crown radius has been taken as 79.5mm. 3. THICKNESS OF HEAD END DISH ASME code section VIII is followed: t = (0.885*P*R)/( σ allow *η-0.1*P) Hence a thickness of 2.0mm is selected for the fabrication aspect, to maintain required concentricity and rigidity during integration, from the point of view of stress concentrations at the opening. 4. 4.1 GRAPHITE THROAT BACKUP MATERIAL: TN = (0.885*P*R)/( σ allow* η) = 5.9mm Keeping design criteria in view the actual thickness proposed for a nozzle would be 5.0mm 4.2 DESIGN OF NOZZLE INSERTS: Bearing load on insert = MEOP* area = 110* π/4* (9.2 2 – 6.8 2 ) = 3317.52 Kg