A particle swarm/pattern search hybrid optimizer was used to drive a solid rocket motor modeling code to an optimal solution. The solid motor code models tapered motor geometries using analytical burn back methods by slicing the grain into thin sections along the axial direction. Grains with circular perforated stars, wagon wheels, and dog bones can be considered and multiple tapered sections can be constructed. The hybrid approach to optimization is capable of exploring large areas of the solution space through particle swarming, but is also able to climb “hills” of optimality through gradient based pattern searching. A preliminary method for designing tapered internal geometry as well as tapered outer mold-line geometry is presented. A total of four optimization cases were performed. The first two case studies examines designing motors to match a given regressive-progressive-regressive burn profile. The third case study studies designing a neutrally burning right circular perforated grain (utilizing inner and external geometry tapering). The final case study studies designing a linearly regressive burning profile for right circular perforated (tapered) grains.
A myriad of design challenges are present in creating a small, lightweight unmanned aerial vehicle (UAV) for entry into the 2008/2009 AIAA Design Build Fly remote-controlled aircraft competition. This year's competition requires a team's aircraft to carry three different store configurations for three distinct missions. This paper presents Auburn University's entry into the competition. The focus of the design was to maximize the scoring algorithms by creating an easily assembled, lightweight aircraft with the ability to complete all tasks quickly. To accomplish this task, a monoplane configuration was designed with rearward folding wings to allow the aircraft to be assembled quickly and to fit into the required box limit. All components were designed for rapid assembly and minimum weight and have been manufactured using materials such as foam, balsa wood, and composite materials. A prototype aircraft was successfully designed, built, and tested. The finished aircraft will compete in the AIAA Design-Build-Fly competition in Tucson, Arizona in April of 2009.
A comprehensive simulation model for a three-stage solid-propellant launch vehicle has been combined with a genetic algorithm to show that aerodynamic assist during early flight of a launch vehicle can substantially improve vehicle performance. Three studies were completed which include a comparison model for the Minuteman-III intercontinental ballistic missile, an improvement to the suborbital phase of flight for a modern ICBM, and the design of a generic three-stage orbital launch vehicle. Significant performance enhancement was achieved by attaching wings to the first stage for providing aerodynamic assist. Optimization was performed by varying the geometric definition of the attached wings and core vehicle design parameters. Significant decreases in initial system weights and propellant mass fractions were achieved for a given payload with the addition of wing structure. These final results are presented in the form of effective specific impulse boost for the aerodynamically assisted vehicle. Nomenclature݃ = gravitational acceleration at Earth's surface ܫ ௦ = specific impulse ܯ = stage initial mass ܯ = stage burnout mass ܯ = stage payload mass ܯ = stage propellant mass ܴܯ = mass ratio ܯ ௦ = stage structural mass Δܸ = change in velocity ߝ = structural coefficient ߣ = payload coefficient
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