Ariane 2010 composite case SRM - An example of multi-disciplinary approach

Abstract

Many heavy launchers use solid rocket boosters (SRBs) for main thrust at lift-off. Ariane 5, for instance, uses SRBs with metallic structure and a three-segment grain. The main objectives of future launcher configurations will be to reduce launch cost, improve performance, and improve payload comfort (lower pressure oscillations levels). One way to improve the Ariane payload is to use redesign composite structure SRM (as a consequence re-optimization of the operating parameters leads to an increase MEOP). From a technical point of view, many grain configuration possibilities exist, and then different grains have to be considered. In order to take maximum mission and performance constraints into account in selecting the grain architecture and geometry, we first optimize the mass flow rate to search maximum payload mass (optimization criterion) . This performance optimization is a multi-disciplinary approach and considers also how structural loads and booster thrust levels affect both vehicle mass and SRBs characteristics (mass and specific impulse mainly). The assumed mass-flow rate is a five-point law with fixed propellant mass and burn time. The levels duration, slope and value are to obtain a two-level law with two mass-flow rates. After this, a grain configuration is sought for which the mass-flow rate variation is as close as possible to the optimized law. Lastly, the payload obtained with the new proposed grain is computed. This completes the first phase of the study and we hope to improve the results by increasing propellant mass, modifying the burn time, and changing some interfaces. ACRONYMS AND NOTATION Ae Nozzle Exhaust Area D Booster External Diameter GTO Geostationary Orbit Isv Vacuum specific impulse L SRM Length MEOP Maximum Expected Operating Pressure Mi Inert Mass Mp Propellant Mass OOP Pressure Oscillations Pdyn Dynamic Pressure PLref Reference Payload Pmax Maximum Pressure SRB Solid Rocket Booster SRM Solid Rocket Motor Tb Burning Time