Aerospace Engineering Commons^™

Cfd Analysis Of A Uni-Directional Impulse Turbine For Wave Energy Conversion, Carlos Alberto Velez

Electronic Theses and Dissertations

Ocean energy research has grown in popularity in the past decade and has produced various designs for wave energy extraction. This thesis focuses on the performance analysis of a uni-directional impulse turbine for wave energy conversion. Uni-directional impulse turbines can produce uni-directional rotation in bi-directional flow, which makes it ideal for wave energy extraction as the motion of ocean waves are inherently bi-directional. This impulse turbine is currently in use in four of the world’s Oscillating Wave Columns (OWC). Current research to date has documented the performance of the turbine but little research has been completed to understand the flow …

Super-Adiabatic Combustion In Porous Media With Catalytic Enhancement For Thermoelectric Power Conversion, Kyle Thomas Mueller

Electronic Theses and Dissertations

The combustion of ultra-lean fuel to air mixtures provides an efficient way to convert the chemical energy of hydrocarbons into useful power. Conventional burning techniques of a mixture have defined flammability limits beyond which a flame cannot self-propagate due to heat losses. Matrix stabilized porous medium combustion is an advanced technique in which a solid porous matrix within the combustion chamber accumulates heat from the hot gaseous products and preheats incoming reactants. This heat recirculation extends the standard flammability limits and allows the burning of ultra-lean fuel mixtures, conserving energy resources, or the burning of gases of low calorific value, …

Translational And Rotational Control Of An Asteroid Orbiting Satellite, Takahiro Kuhara

Doctoral Dissertations and Master's Theses

The objective of this thesis is to analyze an effective control scheme for an asteroid orbiting satellite. The thesis first summarizes the progress made in the dynamics formulation of such satellites and then provides a theoretical framework for the control system design. The control objective is to maintain a nadir pointing attitude on a circular equatorial orbit. Using established control design techniques, feedback laws are constructed to control both rotational and translational motion of the satellite so that the control objective is achieved. Computer simulations are carried out to illustrate the effectiveness of the control laws.

Beading And Dimpling Techniques To Improve The Vibration And Acoustic Characteristics Of Plate Structures, Nabeel Taiseer Alshabtat

Dissertations

A method of improving the vibroacoustic characteristics of beams and plates is presented. This method is based on creating dimples or beads on the surface of the structures. The proposed method couples the finite element method with an optimization technique based on the genetic algorithm (GA). The improvement of the vibroacoustic characteristics of beams and plates is achieved by two separate strategies. The first strategy is optimizing the natural frequencies of beams and plates. The second strategy is minimizing the sound radiation from such vibrating structures. Optimizing the natural frequencies of some types of beams and simply supported plates by …

Ductile Mode Material Removal Of Ceramics And Semiconductors, Deepak Ravindra

Dissertations

Ceramics and semiconductors are hard, strong, inert and lightweight. They also have good optical properties, wide energy bandgap and high maximum current density. This combination of properties makes them ideal candidates for tribological, semiconductor, MEMS and optoelectronic applications respectively. Manufacturing these materials without causing surface and subsurface damage is extremely challenging due to their high hardness, brittle characteristics and poor machinability. However, ductile regime machining of these materials is possible due to the high-pressure phase transformation occurring in the material caused by the high compressive stresses induced by the single point diamond tool tip. In this study, to further augment …

Shock-Associated Noise Generation In Curved Coanda Turbulent Wall Jets, Caroline P. Lubert, Richard J. Shafer

Department of Mathematics and Statistics - Faculty Scholarship

Curved three-dimensional turbulent Coanda wall jets are present in a multitude of natural and engineering applications. The mechanism by which they form a shock-cell structure is poorly understood, as is the accompanying shock-associated noise (SAN) generation. This paper discusses these phenomena from both a modeling and experimental perspective. The Method of Characteristics is used to rewrite the governing hyperbolic partial differential equations as ordinary differential equations, which are then solved numerically using the Euler predictor-corrector method. The effects of complicating factors -- such as radial expansion and streamline curvature -- on the prediction of shock-cell location are then discussed. This …

Continuous Low Thrust For Small Spacecraft Proximity Operations, James Harris Meub

Masters Theses

"Recently, both DoD and NASA have demonstrated increased interest in the development of close proximity operations for space systems. AFRL's Advanced Sciences and Technology Research Institute for Astrodynamics (ASTRIA) has defined several key research topics relevant to military priorities, with one area of critical importance being the inspection and observation of low Earth orbit resident space objects (RSOs). This study investigates the feasibility of using a low-thrust cold-gas propulsion system to effectively and accurately facilitate resident space object inspection. Specifically, this study focuses on the Missouri S&T Satellite mission (M-SAT) as a means to demonstrate autonomous RSO inspection. This paper …

X-51 Composite Airframe, Brendon J. Townshend

Aerospace Engineering

This paper gives an overview of the progress that has been made in the design build of the X-51.  The X-51 is a composite scale replica of a P-51D fuselage integrated with a P-51H wing.  Issues with the airframe as well as current action items are discussed, as well as findings so far in preliminary design.

Mapping Galileo's Trajectory, Mark Woods

Aerospace Engineering

The NASA Galileo mission was mapped out using a patched conics approximation.  Galileo launched from Earth, underwent a gravity assist from Venus back to Earth for another gravity assist.  Galileo then came back to Earth for one more gravity assist to propel it to Jupiter.  A simulation ignoring all perturbations (i.e. third body effects, zonal (harmonics, solar wind, drag) was carried out.  The simulation was able to make it to the final Earth flyby before diverging from the actual trajectory.  The simulated and actual flyby dates all differed by less than 5 hours, and the simulated and actual flyby altitudes …

Analysis Of Surface Augmentation Of Airfoil Sections Via Flow Visualization Techniques, John Louis Vento

Aerospace Engineering

This report details an experiment done to verify the effectiveness of two passive flow control systems on two-dimensional airfoil sections. The flow control was tested on two types of airfoils: a symmetric NACA 0011, intended to represent an airplane in cruise, and a NACA16611, intended to represent an aircraft with flaps extended.  Two types of passive systems were employed, a dimple surface augmentation, similar to a golf ball, and a grit system located at 20% chord. Airfoils without either augmentation were tested as a control case. Using a water tunnel and dye to perform flow visualization, the effects of each …

Flight Testing In A Simulation Based Environment, David W. Babka

Aerospace Engineering

Over the past two decades performance flight testing of full scale aircraft has transferred some of the testing workload to simulation based systems.  Flight testing full scale aircraft in the real world environment has always been expensive, especially now with the rise in aviation fuel costs. Additionally, new emerging technologies require extensive testing and doing so in the full scale environment is cost prohibitive.  A cheaper alternative is to test systems in a simulation based environment.  Not only can aircraft be simulated via a computer, but all the aircrafts systems can be modeled in the simulation.  Furthermore, most of the …

Dynamic Ergonomic Analysis And Simulation Of Fastening Operation, Akul Joshi

Doctoral Dissertations

"Operator performing fastening operation with powered hand-tools at awkward postures is subjected to external forces that may pose a risk of developing ergonomic injuries. For design of safe workplaces and selection of tools it is necessary to identify the probable causes of discomfort by simulating the work conditions and quantifying the risk factors. An ergonomic simulator is developed to simulate the fastening operation and quantify the effects of posture and force in fastening operation. The effect of dynamic forces is analyzed using two approaches. The first approach analyzes the effect of tool vibration while the second analyzes the hand-arm system …

Space Mission Engineering: The New Smad, James R. Wertz, David F. Everett, Jeffery J. Puschell

Robert "Bob" Twiggs STEM Education Collection

A PowerPoint Presentation created by James Wertz, David Everett, and Jeffery J. Puschell on "Space Mission Engineering: The New SMAD" in 2011.

Shaker Table Vibration Testing Of A Microsatellite, Tonya Michelle Sanders

Masters Theses

"In the satellite development process, structural testing is a means to gain confidence in analytical models and ultimately support qualification of the spacecraft for flight. Vibration testing, in particular, is motivated by the safety considerations of crew or launch personnel, the survivability of delicate hardware and electronics, and the avoidance of large stresses that cause structural fatigue or failure. The subject of this thesis is concerned with the shaker table vibration testing of a microsatellite pair designed and built by students at the Missouri University of Science and Technology in Rolla, Missouri. A finite element model (FEM) used in structural …

Hall-Effect Thruster Surface Properties Investigation, David George Zidar

Masters Theses

"Surface properties of Hall-effect thruster channel walls play an important role in the performance and lifetime of the device. Physical models of near-wall effects are beginning to be incorporated into thruster simulations, and these models must account for evolution of channel surface properties due to thruster operation. Results from this study show differences in boron nitride channel surface properties from beginning-of-life and after 100's of hours of operation. Two worn thruster channels of different boron nitride grades are compared with their corresponding pristine and shadow-shielded samples. Pristine HP grade boron nitride surface roughness is 9000±700 Å, while the worn sample …

Determination Of Critical Parameters For Solar Probe Plus Shielding, Sergio Rafael Mendez

Open Access Theses & Dissertations

A methodology to determine critical design parameters such as critical "design" particle size, and critical "design" impact speed for the shielding of the Solar Probe Plus spacecraft was developed in this thesis. Several critical components and surfaces of the spacecraft such as the Solar Array North, the Thermal Protection System, and the ISIS Instruments were analyzed in this study. The methodology determines the critical "design" particle size based on the required reliability or probability of no impact. Current NASA methods do not provide means to calculate critical "design" impact speeds for missions such as Solar Probe Plus, where the distributions …

Development Of A Heat Transfer Test Rig For Finding Heat Transfer Characteristics Of Liquid Methane, Sergio Flores

Open Access Theses & Dissertations

Most large scale rocket engines use a regeneratively cooled system to cool the rocket engine using either the rocket fuel or oxidizer. The use of liquid methane as a rocket fuel is an emerging technology proving to have several advantages over current rocket fuels. However, liquid methane is lacking the extensive research as a rocket fuel compared to highly used rocket fuels like liquid hydrogen. A heat transfer test rig was built with the goal to characterize the heat transfer characteristics of liquid methane as it passes through a heated channel. The development of the test rig underwent considerations designed …

The Effect Of Mmod Porosity On Crater Depth After Hypervelocity Impact, David Ledesma

Open Access Theses & Dissertations

A significant amount of research has been conducted in the last decades on the design of spacecraft shielding for the impacts of Micro Meteoroid and Orbital Debris (MMOD). Through the use of hydrocodes, empirical data, and physical testing, researchers have been successful in studying a wide range of shielding configurations. However, a very limited amount of research has been conducted to understand the effect that the porosity and irregular shape of MMOD has on the damage they create on spacecraft components.

The work presented in this thesis addresses the modeling of MMDO porosity by using the CTH hydrocode to investigate …

Design And Cfd Optimization Of Methane Regenerative Cooled Rocket Nozzles, Christopher Linn Bradford

Open Access Theses & Dissertations

Liquid rocket engines benefit in life cycle from the active regenerative cooling method which passes the fuel as the coolant through channels surrounding the combustion chamber. These channels are designed and optimized using structural considerations as well as heat transfer theory, then CFD simulations with the software FLUENT are performed for the final analysis. The difficulty in using methane as the fuel/coolant is addressed, and requires the use of the ideal gas numerical model in preliminary CFD simulations. Comparison to real gas numerical models is made, and results also given for one channel design. The techniques utilized herein allow the …

Uncertainty Quantification Integrated To Computational Fluid Dynamic Modeling Of Synthetic Jet Actuators, Srikanth Adya

Masters Theses

"The Point Collocation Non-Intrusive Polynomial Chaos (NIPC) method was applied to a stochastic synthetic jet actuator problem to demonstrate the integration of computationally efficient uncertainty quantification to the high-fidelity CFD modeling of Synthetic Jet Actuators. The uncertainty quantification approach was first implemented in two stochastic model problem cases for the prediction of peak exit plane velocity using a Fluid Dynamic Based analytical model of the Synthetic Jet Actuator, which is computationally less expensive than CFD simulations. The NIPC results were compared with direct Monte Carlo sampling results. To demonstrate the efficient uncertainty quantification in CFD modeling of synthetic jet actuators, …