Thrust vector control study for large /260 inch/ rocket motor applications

Design concepts of thrust vector control for large rocket motor application

Centaur Propellant Thermal Conditioning Study

A wicking investigation revealed that passive thermal conditioning was feasible and provided considerable weight advantage over active systems using throttled vent fluid in a Centaur D-1s launch vehicle. Experimental wicking correlations were obtained using empirical revisions to the analytical flow model. Thermal subcoolers were evaluated parametrically as a function of tank pressure and NPSP. Results showed that the RL10 category I engine was the best candidate for boost pump replacement and the option showing the lowest weight penalty employed passively cooled acquisition devices, thermal subcoolers, dry ducts between burns and pumping of subcooler coolant back into the tank. A mixing correlation was identified for sizing the thermodynamic vent system mixer. Worst case mixing requirements were determined by surveying Centaur D-1T, D-1S, IUS, and space tug vehicles. Vent system sizing was based upon worst case requirements. Thermodynamic vent system/mixer weights were determined for each vehicle

Hypersonic test facility Patent

Hypersonic test facility for studying ablation in models under high pressure and high temperatur

Feasibility study of silicon nitride protection of plastic encapsulated semiconductors

The application of low temperature silicon nitride protective layers on wire bonded integrated circuits mounted on lead frame assemblies is reported. An evaluation of the mechanical and electrical compatibility of both plasma nitride and photochemical silicon nitride (photonitride) passivations (parallel evaluations) of integrated circuits which were then encapsulated in plastic is described. Photonitride passivation is compatible with all wire bonded lead frame assemblies, with or without initial chip passivation. Plasma nitride passivation of lead frame assemblies is possible only if the chip is passivated before lead frame assembly. The survival rate after the environmental test sequence of devices with a coating of plasma nitride on the chip and a coating of either plasma nitride or photonitride over the assembled device is significantly greater than that of devices assembled with no nitride protective coating over either chip or lead frame

Research in satellite-aided crop inventory and monitoring

Automated information extraction procedures for analysis of multitemporal LANDSAT data in non-U.S. crop inventory and monitoring are reviewed. Experiments to develope and evaluate crop area estimation technologies for spring small grains, summer crops, corn, and soybeans are discussed

Effect of Vegetation on Transport of Groundwater and Non-aqueous Phase Liquid Contaminants

An aquifer model system was established to examine and delineate the presence, fate and transport of nonaqueous-phase liquid (NAPL) contaminants. The system consists of six independent channels with identical dimensions. The channels were constructed with steel bottoms, side panels, and end panels. Trichloroethylene (TCE) was selected as a representative compound to model NAPL groundwater contaminants in the saturated zone of the aquifer. The flow regime of groundwater in the saturated zone was investigated by conducting a bromide tracer experiment. The movement of TCE in both horizontal and vertical directions was studied by monitoring the ground- water effluent stream and the gas phase at the soil surface after a pulse injection of liquid TCE into each channel at the bottom inlet. A multistage compartment model was developed to help interpret the experimental data and observations

Evaluation of half wave induction motor drive for use in passenger vehicles

Research performed at the University of Missouri-Columbia to devise and design a lower cost inverter induction motor drive for electrical propulsion of passenger vehicles is described. A two phase inverter motor system is recommended. The new design is predicted to provide comparable vehicle performance, improved reliability and a cost advantage for a high production vehicle, decreased total rating of the power semiconductor switches, and a somewhat simpler control hardware compared to the conventional three phase bridge inverter motor drive system. The major disadvantages of the two phase inverter motor drive are that it is larger and more expensive than a three phase machine, the design of snubbers for the power leakage inductances produce higher transient voltages, and the torque pulsations are relatively large because of the necessity to limit the inverter switching frequency to achieve high efficiency

Modeling the Fate of Toluene in a Chamber with Alfalfa Plants: 1. Theory and Modeling Concepts

A model was developed to investigate the fate of organic contaminants in soils in the presence of vegetation. The model has two modules. The first module simulates the soil-water and root-water pressure heads under the influence of water extraction by the roots of growing vegetation. Evapotranspiration due to alfalfa plants is an outflux boundary condition at the soil surface for this model. The distributions for water and air contents and Darcy water flux are obtained from the soil-water pressure heads. The second module simulates the fate of soil constituents in the porous medium using the Darcy water flux. The constituents assumed to be present in vegetated soil were contaminant, biomass, oxygen, and root exudates. A Galerkin finite element method was used to solve the model equations in two dimensions to enable comparison with an experimental system. The domain simulating the experimental chamber was assumed to be comprised of rectangular elements with bilinear shape functions which represented the variations within each element. Convergence to solution for the non-linear equations was accomplished using the Picard iterative algorithm. The time derivative was approximated using an implicit Crank-Nicholson scheme

Modeling the Fate of Toluene in a Chamber with Alfalfa Plants: 2. Numerical Results and Comparison Study

Investigations were conducted in a chamber to study the role of alfalfa plants in bioremediating toluene. Modeling and experimental results indicate that in situ bioremediation of toluene in the presence of plants is feasible and economical. This is primarily due to evapotranspiration which greatly enhances the vertical transport of dissolved contaminants from the saturated zone to the rhizosphere, thereby increasing the possibility of aerobic degradation. The fate of toluene was simulated and monitored for groundwater contaminated with toluene at saturated concentrations. FT-IR instrumentation was used to monitor toluene in the headspace gas of the vegetated chamber. Overall mass balance, based on groundwater and headspace measurements, indicated about 75% loss or biodegradation of toluene from the chamber during steady state. Evolution of significant amounts of CO2 accounted for mineralization of toluene. Simulation results predicted toluene biodegradation in the unsaturated zone where both oxygen and toluene were present. Dispersion processes in the soil were characterized by bromide tracer analysis. Predictions from simulations were compared with the water content and toluene concentrations measured in the chamber