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A laser-induced fluorescence technique for conducting planar measurements of temperature, pressure, and velocity in nonreacting, compressible flows has been developed, validated, and demonstrated. Planar fluorescence from iodine, seeded into air, was induced by an argon-ion laser and collected using a liquid-nitrogen cooled charge-coupled device camera. The temperature measurement, which has been described earlier, is used in conjunction with a sophisticated model of the fluorescence excitation spectrum to produce accurate pressure measurements. The demonstration velocity measurements represent the first planar velocity mapping using molecular seed in a highly three-dimensional supersonic flow of practical importance. In the measurement technique, temperature is determined from the fluorescence induced with the laser-operated broadband. Pressure and velocity are determined from the shape and position of the fluorescence excitation spectrum, which is measured with the laser operated narrow band. A parametric relationship has been developed to relate the complex fluorescence excitation spectrum to pressure for specified temperatures. The importance of this novel approach is that it significantly reduces the computational requirements for relating the line shape to pressure, thereby making accurate measurements of pressure at a large number of points in a plane practical. The uncertainty of the measurement is estimated to be 6% for temperature, 5% for pressure, and 25 m/s for velocity.

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A technique is described for imaging the injectant mole-fraction distribution in nonreacting compressible mixing flow fields. Planar fluorescence from iodine, seeded into air, is induced by a broadband argon-ion laser and collected using an intensified charge-injection-device array camera. The technique eliminates the thermodynamic dependence of the iodine fluorescence in the compressible flow field by taking the ratio of two images collected with identical thermodynamic flow conditions but different iodine seeding conditions. The resulting images are, to our knowledge, the first quantitative planar measurements of mole-fraction distributions in a nonreacting compressible flow field and allow mixing to be studied directly.

This paper describes an effort to optimize the design of an entire space launch vehicle to low Earth (circular) orbit, consisting of multiple stages using a genetic algorithm with the goal of minimizing vehicle weight and ultimately vehicle cost. The entire launch vehicle system is analyzed using various multistage configurations to reach low Earth orbit. Specifically, three-and four-stage solid propellant vehicles have been analyzed. The vehicle performance modeling requires that analysis from four separate disciplines be integrated into the design optimization process. The disciplines of propulsion characteristics, aerodynamics, mass properties, and flight dynamics have been integrated to produce a high-fidelity system model of the entire vehicle. In addition, the system model has been validated using the existing launch vehicle data. The cost model is mass based and uses extensive historical data to produce a cost estimating relationship for a solid propellant vehicle. For the design optimization, the goal is for the genetic algorithm to minimize the differences between the desired and actual orbital parameters. This ensures that the payload achieves the desired orbit. One final goal is to minimize the overall vehicle mass, thus minimizing the system cost per launch. This paper will represent the first effort of its kind to minimize the solid propellant launch vehicle cost at the preliminary design level using a genetic algorithm.

This paper describes an effort to optimize the design of an entire space launch vehicle to low-Earth (circular) orbit, consisting of multiple stages using a genetic algorithm (GA) with the goal of minimizing vehicle weight and ultimately vehicle cost. The entire launch vehicle system is analyzed using various multistage configurations to reach low-Earth orbit. Specifically, three and four-stage solid propellant vehicles have been analyzed. The vehicle performance modeling requires that analysis from four separate disciplines be integrated into the design optimization process. The disciplines of propulsion characteristics, aerodynamics, mass properties and flight dynamics have been integrated to produce a high fidelity system model of the entire vehicle. In addition, the system model has been validated using existing launch vehicle data. The cost model is mass-based and uses extensive historical data to produce a cost estimating relationship for a solid propellant vehicle. For the design optimization, the goals of the problem are for the GA to minimize the differences between the desired and actual orbital parameters. This ensures the payload achieves the desired orbit. One final goal is to minimize the overall vehicle mass thus minimizing the system cost per launch. The paper will represent the first effort of its kind to minimize solid propellant launch vehicle cost at the preliminary design level using a GA.

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