Aerospace Engineering Commons^™

The Influence Of Viscosity And Surface Curvature On The Pressure Distribution Of A Stream Thrust Probe, Renee Pasman, Russell M. Cummings

Aerospace Engineering

Determining the local stream thrust (a vector quantity) from a measured pitot pressure (a scalar quantity) requires either knowledge of the flow direction, or a probe shape that compensates for flow direction. This compensation would ideally make the measured pressure directly proportional to the component of momentum along the probe axis. The flow angle sensitivity required to resolve this component of momentum was determined theoretically previously. A proposed probe nose shape was analyzed using CFD and found to produce flow angle sensitivity close to the required sensitivity. The proposed nose shape was also tested in a wind tunnel at Mach …

Numerical Evaluation Of The Flowfield For A High Fineness Ratio Body With Drag Brakes, Russell M. Cummings, James A. Divine, Thomas R. Yechout, David C. Wetlesen, Joseph J. Kealos

Aerospace Engineering

The Advanced Remote Ground Unattended Sensor (ARGUS) utilizes drag brakes to control its terminal velocity during flight. Computational fluid dynamics predictions were performed at Mach numbers between 0.20 and 0.95 with a full scale model of the ARGUS configuration at conditions to match wind tunnel testing that has been performed at the USAFA Subsonic Wind Tunnel. Configurations consist of brakes fully deployed for a nominal brake fin and a perforated brake fin. Steady-stated computations were performed using the Spalart-Allmaras turbulence model at angles of attack between 0 degrees to 20 degrees at roll angles of 0 degrees and 45 degrees. …

Nonlinear Model Predictive Control Technique For Unmanned Air Vehicles, Nathan Slegers, Jason Kyle, Mark Costello

Faculty Publications - Biomedical, Mechanical, and Civil Engineering

A nonlinear model predictive control strategy is developed and subsequently specialized to autonomous aircraft that can be adequately modeled with a rigid 6-degrees-of-freedom representation. Whereas the general air vehicle dynamic equations are nonlinear and nonaffine in control, a closed-form solution for the optimal control input is enabled by expanding both the output and control in a truncated Taylor series. The closed-form solution for control is relatively simple to calculate and well suited to the real time embedded computing environment. An interesting feature of this control law is that the number of Taylor series expansion terms can be used to indirectly …

Cool Flames At Terrestrial, Partial, And Near-Zero Gravity, Michael R. Foster, Howard Pearlman

Faculty Publications - Biomedical, Mechanical, and Civil Engineering

Natural convection plays an important role in all terrestrial, Lunar, and Martian-based, unstirred, static reactor cool flame and low-temperature autoignitions, since the Rayleigh number (Ra) associated with the self-heating of the reaction exceeds the critical Ra (approximately 600) for onset of convection. At near-zero gravity, Ra < 600 can be achieved and the effects of convection suppressed. To systematically vary the Ra without varying the mixture stoichiometry, reactor pressure, or vessel size, cool flames are studied experimentally in a closed, unstirred, static reactor subject to different gravitational accelerations (terrestrial, 1g; Martian, 0.38g; Lunar, 0.16g; a n dr e - duced gravity, ∼10−2g). Representative results show the evolution of the visible light emission using an equimolar n-butane:oxygen premixture at temperatures ranging from 320 to 350 ◦C (593–623 K) at subatmospheric pressures. For representative reduced-gravity, spherically propagating cool flames, the flame radius based on the peak light intensity is plotted as a function of time and the flame radius (and speed) is calculated from a polynomial fit to data. A skeletal chemical kinetic Gray-Yang model developed previously for a one-dimensional, reactive– diffusive system by Fairlie and co-workers is extended to a two-dimensional axisymmetric, spherical geometry. The coupled species, energy, and momentum equations are solved numerically and the spatio-temporal variations in the temperature profiles are presented. A qualitative comparison is made with the experimental results.

Basic Materials Research Programs At The U.S. Air Force Office Of Scientific Research, Herbert C. Carlson, K. C. Goretta

United States Air Force: Publications

The Air Force Office of Scientific Research (AFOSR) annually sponsors approximately 5000 research scientists at 1000 universities and laboratories, generating about 10,000 Ph.D. graduates per decade, all expected to publish their basic research findings in peer-reviewed journals. After a brief introduction of the nature of AFOSR’s support to basic research in the U.S. and international scientific communities, work it supports at the frontiers of materials science is highlighted. One focused research theme that drives our investment is the MEANS program. It begins with the end in mind; materials are designed with practicable manufacture as an explicit initial goal. AFOSR’s broad …

Atomic Force Microscope Tip Spontaneous Retraction From Dielectric Surfaces Under Applied Electrostatic Potential, S. F. Lyuksyutov, P. B. Paramonov, O. V. Mayevska, M. A. Reagan, E. Sancaktar, R. A. Vaia, S. Juhl

United States Air Force: Publications

A time-resolved method for tip’ retraction at µs-scale away from dielectric surfaces has been developed. Analysis of the forces in the system comprising AFM tip, water meniscus, and polymer film suggests that an electrostatic repulsion of the tip from the surface in the double-layered (water and polymer) system, and water condensation in the tip–surface junction are the dominant factors enabling the mechanical work for tip retraction. Nanostructures of 5–80nm height are formed in polymeric surfaces as a result. This interesting physical phenomenon could be used for nanostructures patterning in polymeric materials at enhanced aspect ratio.

Continuing Evolution Of Aerodynamic Concept Development Using Collaborative Numerical And Experimental Evaluations, Russell M. Cummings, Scott A. Morton

Aerospace Engineering

Traditionally, computational predictions and experimental evaluations of aerodynamic concepts have been conducted separately, with little collaboration other than post priori comparisons of results. This has led to distrust and even antagonism between the computational and the experimental communities. These difficulties probably began when early computational fluid dynamic practitioners boasted that wind tunnels would become secondary in aerodynamic concept development within a few short years, a prediction that has not come true. On the contrary, it is believed that a great deal of synergy can be cultivated when computational and experimental evaluations are conducted in an integrative fashion. A variety of …

Critical Hypersonic Aerothermodynamic Phenomena, John J. Bertin, Russell M. Cummings

Aerospace Engineering

The challenges in understanding hypersonic flight are discussed and critical hypersonic aerothermodynamics issues are reviewed. The ability of current analytical methods, numerical methods, ground testing capabilities, and flight testing approaches to predict hypersonic flow are evaluated. The areas where aerothermodynamic shortcomings restrict our ability to design and analyze hypersonic vehicles are discussed, and prospects for future capabilities are reviewed. Considerable work still needs to be done before our understanding of hypersonic flow will allow for the accurate prediction of vehicle flight characteristics throughout the flight envelope from launch to orbital insertion.

Perchlorate Toxicity And Risk Assessment, David R. Mattie, Joan Strawson, Jay Zhao

United States Air Force: Publications

Ammonium perchlorate is the oxidizer ingredient in solid propellant mixtures for rockets, missiles and munitions such as Titan, Minuteman, Peacekeeper, Hawk, Polaris and the Space Shuttle. Perchlorate salts may also be used in medicine, matches, munitions and pyrotechnics (illuminating and signaling flares, colored and white smoke generators, tracers, incendiary delays, fuses, photo-flash compounds and fireworks). Perchlorate is also found in lubricating oils, finished leather, fabric fixer, dyes, electroplating, aluminum refining, manufacture of rubber, paint and enamel production, as an additive in cattle feed, in magnesium batteries and as a component of automobile air bag inflators.'

Atomic Force Microscopy Of Bacillus Spore Surface Morphology, Ruth A. Zolock, Guangming Li, Charles Bleckmann, Larry Burggraf, Douglas C. Fuller

United States Air Force: Publications

Bacillus spore surface morphology was imaged with atomic force microscopy (AFM) to determine if characteristic surface features could be used to distinguish between four closely related species; Bacillus anthracis Sterne strain, Bacillus thuringiensis var. kurstaki, Bacillus cereus strain 569, and Bacillus globigii var. niger. AFM surface height images showed an irregular topography across the curved upper surface of the spores. Phase images showed a superficial grain structure with different levels of phase contrast and significant differences in average surface morphologies among the four species. Although spores of the same species showed similarities, there was significant variability within each …

Field-Scale Demonstration Of Induced Biogeochemical Reductive Dechlorination At Dover Air Force Base, Dover, Delaware, Lonnie G. Kennedy, Jess W. Everett, Erica Becvar, Donald Defeo

United States Air Force: Publications

Biogeochemical reductive dechlorination (BiRD) is a new remediation approach for chlorinated aliphatic hydrocarbons (CAHs). The approach stimulates common sulfate-reducing soil bacteria, facilitating the geochemical conversion of native iron minerals into iron sulfides. Iron sulfides have the ability to chemically reduce many common CAH compounds including PCE, TCE, DCE, similar to zero valent iron (Fe⁰). Results of a field test at Dover Air Force Base, Dover, Delaware, are given in this paper. BiRD was stimulated by direct injection of Epson salt (MgSO₄·7H₂O) and sodium (L) lactate (NaC₃H₅O₃) in five …

Creating Cross-Over Vehicles: Defining And Combining Vehicle Classes Using Shape Grammars, Seth D. Orsborn, R. Pawlicki, R. Smith, Jonathan Cagan

Mechanical and Aerospace Engineering Faculty Research & Creative Works

In the push for new vehicle designs, the distinctions between vehicle classes are quickly becoming blurred. We use shape grammars to quantify the differences between vehicle classes through the application of class-specific rules and the constraint of rule applications to within parametric ranges determined for each class. This allows for the development of new vehicle forms that clearly fall within a class or purposefully cross over the boundaries of classes and mix rules and ranges to create unique and interesting cross-over vehicles.

Design And Fabrication Of A Full-Featured Labscale Hybrid Rocket Engine, Kyle Platt

Electronic Theses and Dissertations

The design, development, integration and testing of a full-featured, Lab-Scale Hybrid Rocket Engine was not only envisioned to be the chosen method of putting student payloads into space, but to be an invaluable teaching resource. The subject of the present thesis is the analysis, design, development, integration and demonstration of a lab-scale hybrid rocket motor. The overarching goal of this project was to establish a working developmental lab model from which further research can be accomplished. The lab model was specifically designed to use a fuel source that could be studied in normal laboratory conditions. As such, the rocket engine …

Autonomous Controls Algorithmfor Formation Flying Of Satellites, Luis Santiago

Electronic Theses and Dissertations

This document describes the design and analysis of the Navigation, Guidance and Control System for the KnightSat project. The purpose for the project is to test and demonstrate new technologies the Air Force would be interested in for research and development. The primary mission of KnightSat is to show how a constellation of satellites can maintain relative position with each other autonomously using the Microwave Electro Thermal (MET) thruster. The secondary mission is to use multiple satellite imagery to obtain 3 dimensional stereo photographs of observable terrain. Formation flying itself has many possible uses for future applications. Selected missions that …

A Sustainable, Systematic Process For Continuous Program Improvement, Nikos J. Mourtos

Faculty Publications

The USA Accreditation Board for Engineering and Technology (ABET) adopted recently a new set of criteria for evaluating engineering programmes. One of these (criterion 3) refers to programme outcomes and assessment. In this article, the author describes the design and implementation of a sustainable, systematic process for defining and assessing programme outcomes. This process involves analysing each outcome into elements, defining a set of attributes for each element, selecting outcome indicators and performance targets, and developing special rubrics for an accurate assessment of student skills. The author also describes a systematic way of addressing specific programme outcomes through course and …

Regulation Of Powder Mass Flow Rate In Gravity-Fed Powder Feeder Systems, Vishnu Thayalan, Robert G. Landers

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Precise regulation of powder mass flow in laser-based manufacturing processes is critical to achieving excellent part dimensional and microstructure quality. Control of powder mass flow is challenging because low flow rates, where nonlinear effects are significant, are typically required. Also, gravity-fed powder feeder systems have significant material transport delays, making the control of powder mass flow even more challenging. This paper presents a control strategy for regulating the powder mass flow rate in a gravity-fed powder feeder system. A dynamic model of the powder feeder system, including material transport delay, is constructed, and a modified proportional plus integral (PI) controller …

Response To "Comment On Variational Approach To The Volume Viscosity Of Fluids" [Phys. Fluids 18, 109101 (2006)], Allen J. Zuckerwar, Robert L. Ash

Mechanical & Aerospace Engineering Faculty Publications

We respond to the Comment of Markus Scholle and therewith revise our material entropy constraint to account for the production of entropy. (c) 2006 American Institute of Physics.

Galileo Probe, Monish Ranjan Chatterjee

Electrical and Computer Engineering Faculty Publications

The Galileo mission to Jupiter was formally approved by the United States Congress in 1977, several years before the space shuttle Columbia made its maiden flight into Earth orbit. The mission was a cooperative project involving scientists and engineers from the United States, Germany, Canada, Great Britain, France, Sweden, Spain, and Australia. Even though the Voyager 1 and Voyager 2 spacecraft had performed flybys of planet Jupiter and its sixteen moons in 1979, the Galileo mission was envisioned to initiate several novel observations of Jupiter, the most massive gas planet of the solar system, and its principal moons, and conduct …

Force Protection Using Composite Sandwich Structures, R. L. Sierakowski, M. L. Hughes

United States Air Force: Publications

In the recent past, advances have been made in the attempt to utilize composite materials as components in protective structures such as those employed by the Air Force to secure critical military assets. In such applications, where lightweight materials that exhibit large levels of energy absorption and high strength/stiffness characteristics are desirable, composite sandwich constructions offer an attractive solution.

In an attempt to evaluate the suitability of certain sandwich structures for use in force protection applications, several sandwich constructions with somewhat novel core materials were identified. A group of thermoplastic core materials have been developed that possess features of both …

United States Air Force Posture Statement 2006, U.S. Air Force

United States Air Force: Publications

Over a century ago, America crossed the threshold of powered flight and gave wings to the world. Soon military leaders realized the implications of this development, and warfare was changed forever. America was fortunate to have "Great Captains" with the vision to imagine the possibilities of air and space power - Airmen like Billy Mitchell, Frank Andrews, Hap Arnold, Ira Eaker, Jimmy Doolittle, Bennie Schriever. They have given us a proud heritage of courage, excellence and innovation. In so doing, they also give us a sense of perspective and a way to understand the Air Force's future.

Analysis Of Damage In Laminated Automotive Glazing Subjected To Simulated Head Impact, Shuangmei Zhao, Li Chai, S. D. Barbat, Lokeswarappa R. Dharani

Mechanical and Aerospace Engineering Faculty Research & Creative Works

During vehicle accidents, occupant's head impacting on windshield or side window is commonly observed. Any attempt to design glazing that minimizes injury to and death of occupants during a vehicle accident requires a thorough understanding of the mechanical behavior of automotive glazing subjected to head impact loads. A continuum damage mechanics (CDM) based constitutive model is developed and implemented into an axisymmetric finite element model to study the failure and impact resistance of laminated automotive glazing subjected to simulated head impact. An anisotropic elastic damage tensor with a linear damage evolution law is chosen to model the failure of the …

Effect Of Operator Control Configuration On Unmanned Aerial System Trainability, John Neumann

Electronic Theses and Dissertations

Unmanned aerial systems (UAS) carry no pilot on board, yet they still require live operators to handle critical functions such as mission planning and execution. Humans also interpret the sensor information provided by these platforms. This applies to all classes of unmanned aerial vehicles (UAV's), including the smaller portable systems used for gathering real-time reconnaissance during military operations in urban terrain. The need to quickly and reliably train soldiers to control small UAS operations demands that the human-system interface be intuitive and easy to master. In this study, participants completed a series of tests of spatial ability and were then …

Reduction Of Vortex-Driven Oscillations In A Solid Rocket Motor Cold Flow Simulation Through Active Control, Jami Ward

Electronic Theses and Dissertations

Control of vortex-driven instabilities was demonstrated via a scaled-down, cold-flow simulation that modeled closed-end acoustics. When vortex shedding frequencies couple with the natural acoustic modes of a choked chamber, potentially damaging low-frequency instabilities may arise. Although passive solutions can be effective, an active control solution is preferable. An experiment was performed to demonstrate an active control scheme for the reduction of vortex-driven oscillations. A non-reacting experiment using a primary flow of air, where both the duct exit and inlet are choked, simulated the closed-end acoustics. Two plates, separated by 1.27 cm, produced the vortex shedding phenomenon at the chamber's first …

Evaluation Of Space Shuttle Tile Subnominal Bonds, Cooper Snapp

Electronic Theses and Dissertations

This study researched the history of Space Shuttle Reusable Surface Insulation which was designed and developed for use on the United States Orbiter fleet to protect from the high heating experienced during reentry through Earth's atmosphere. Specifically the tile system which is attached to the structure by the means of an RTV adhesive has experienced situations where the bonds are identified as subnominal. The history of these subnominal conditions is presented along with a recent identification of a subnominal bond between the Strain Isolation Pad and the tile substrate itself. Tests were run to identify the cause of these subnominal …

Robustness And Control Of A Magnetically Levitated Transportation System, Grzegorz Oleszczuk

Mechanical & Aerospace Engineering Theses & Dissertations

Electromagnetic suspension of Magnetic Levitation Vehicles (Maglev) has been studied for many years as an alternative to wheel-on rail transportation systems. In this work, design and implementation of control systems for a Maglev laboratory experiment and a Maglev vehicle under development at Old Dominion University are described. Both plants are modeled and simulated with consideration of issues associated with system non-linearity, structural flexibility and electromagnetic force modeling. Discussion concerning different control strategies, namely centralized and decentralized approaches are compared and contrasted in this work. Different types of electromagnetic non-linearities are considered and described to establish a convenient method for modeling …

Development Of A Nonlinear Estimator-Based Model Of Pilot Performance During Brownout Conditions, Karl Ulrich Schultz

Mechanical & Aerospace Engineering Theses & Dissertations

During conditions of visual occlusion, pilots are forced to rapidly adapt their scan to accommodate the new observable states via instruments rather than the visual environment. During this transition, the provision of aircraft state information via other than visual modalities improves pilot performance presumably through the increase in situational awareness provided immediately following the visual occlusion event.

The Tactile Situational Awareness System (TSAS) was developed to provide continuous position information to the pilot via tactile rather than visual means. However, as a low-resolution display, significant preprocessing of information is required to maximize utility of this new technology.

Development of a …

Variational Approach To The Volume Viscosity Of Fluids, Allan J. Zuckerwar, Robert L. Ash

Mechanical & Aerospace Engineering Faculty Publications

The variational principle of Hamilton is applied to develop an analytical formulation to describe the volume viscosity in fluids. The procedure described here differs from those used in the past in that a dissipative process is represented by the chemical affinity and progress variable (sometimes called "order parameter") of a reacting species. These state variables appear in the variational integral in two places: first, in the expression for the internal energy, and second, in a subsidiary condition accounting for the conservation of the reacting species. As a result of the variational procedure, two dissipative terms appear in the Navier-Stokes equation. …

An Internet Based Intelligent Argumentation System For Collaborative Engineering Design, Xiaoqing Frank Liu, Samir Raorane, Man Zheng, Ming-Chuan Leu

Computer Science Faculty Research & Creative Works

Modern product design is a very complicated process which involves groups of designers, manufacturers, suppliers, and customer representatives. Conflicts are unavoidable in collaboration among multiple stakeholders, who have different objectives, requirements, and priorities. Unfortunately, current web-based collaborative engineering design systems do not support collaborative conflict resolution. In this paper, we will develop an intelligent computational argumentation model to enable management of a large scale argumentation network, and resolution of conflicts based on argumentation from many participants. A web-based intelligent argumentation tool is developed as a part of a web-based collaborative engineering design system based on the above model to resolve …

A Non-Intrusive Polynomial Chaos Method For Uncertainty Propagation In Cfd Simulations, Serhat Hosder, R. Perez, Robert W. Walters

Mechanical and Aerospace Engineering Faculty Research & Creative Works

An inexpensive non-intrusive polynomial chaos (NIPC) method for the propagation of input uncertainty in CFD simulations is presented. The method is straightforward to implement for any stochastic fluid dynamics problem and computationally less expensive than sampling or quadrature based non-intrusive methods. To validate the present NIPC approach, the method has been applied to: (1) an inviscid oblique shock wave problem with geometric uncertainty, (2) an inviscid expansion wave problem with geometric uncertainty, and (3) a subsonic, two-dimensional, laminar boundary layer flow over a flat plate with an uncertain free-stream dynamic viscosity. For all test cases, the statistics (mean and the …

Effects Of Welding Current In Gas Metal Arc Welding, Junling Hu, Tai Lung Tsai

Mechanical and Aerospace Engineering Faculty Research & Creative Works

In gas metal arc welding (GMAW), current is one of the most important factors affecting the mode of metal transfer, weld pool dynamics and subsequently the weld quality. in this paper, the comprehensive model recently developed by the authors was used to study the effects of different current levels on the droplet formation, plasma generation, metal transfer, and weld pool dynamics in GMA welding. Two welding currents were studied, including one low current and one high current. at each current level, the transient temperature and velocity distributions of the arc plasma and the molten metal, and the shapes of the …