Aerospace Engineering Commons^™

Pressure And Flow Validation Of A Second Generation Gas Extraction Probe For A Hybrid Rocket Gas Extraction System, Constance Meadors, Andrew B. Wright

Journal of the Arkansas Academy of Science

A gas extraction system (GES) has been designed for use with the hybrid rocket facility at the University of Arkansas at Little Rock (UALR) for spectroscopic analysis of rocket plumes. While monitoring gas flow-rate and pressure, the GES extracts gases from the hybrid rocket plume and transports them to a mass spectrometer. This paper describes design and construction of a gas extraction probe (GEP) prototype capable of extracting gases directly from the plume. Gas dynamics equations were used to design two venturi-type GEP, converging and converging-diverging. The probe was tested with air to verify design assumptions. Flow rate through the …

Advances In Space Radiation Shielding Codes, John W. Wilson, Ram K. Tripathi, Garry D. Qualls, Francis A. Cucinotta, Richard E. Prael, John W. Norbury, John H. Heinbockel, John Tweed, Giovanni De Angelis

Mathematics & Statistics Faculty Publications

Early space radiation shield code development relied on Monte Carlo methods and made important contributions to the space program. Monte Carlo methods have resorted to restricted one-dimensional problems leading to imperfect representation of appropriate boundary conditions. Even so, intensive computational requirements resulted and shield evaluation was made near the end of the design process. Resolving shielding issues usually had a negative impact on the design. Improved spacecraft shield design requires early entry of radiation constraints into the design process to maximize performance and minimize costs. As a result, we have been investigating high-speed computational procedures to allow shield analysis from …

A New Optimal Nonlinear Control Method And Its Application To Missile Guidance Law Design, Ming Xin, S. N. Balakrishnan

Mechanical and Aerospace Engineering Faculty Research & Creative Works

In this paper, a new nonlinear control synthesis technique (q-D approximation) is discussed. By adding perturbations to the cost function this approach achieves a suboptimal solution to the Hamilton-Jacobi- Bellman (HJB) equation. By manipulating the perturbation terms both asymptotic stability and optimality properties are obtained. An application to the design of missile guidance law is presented and is compared with a similar technique (State Dependent Riccati Equation technique) used in problems of this class. © 2002 by the author(s).

State Dependent Riccati Equation Based Spacecraft Attitude Control, Ming Xin, S. N. Balakrishnan

Mechanical and Aerospace Engineering Faculty Research & Creative Works

We present a new optimal control approach to the robust spacecraft attitude control in the framework of State Dependent Riccati Equation (SDRE) technique. To treat this highly nonlinear control system, we formulate it as a nonlinear optimal regulator problem. SDRE technique was well applied to this class of attitude control problem. We also synthesize a neural network based extra controller to achieve the robustness in the presence of the parameter uncertainties. A general spacecraft attitude regulation problem was studied to show the effectiveness of SDRE approach and robust extra control design. © 2002. Published by the American Institute of Aeronautics …

A Functional Basis For Engineering Design: Reconciling And Evolving Previous Efforts, Julie Hirtz, Robert B. Stone, Daniel A. Mcadams, Simon Szykman, Kristin L. Wood

Mechanical and Aerospace Engineering Faculty Research & Creative Works

In engineering design, all products and artifacts have some intended reason behind their existence: the product or artifact function. Functional modeling provides an abstract, yet direct, method for understanding and representing an overall product or artifact function. Functional modeling also strategically guides design activities such as problem decomposition, physical modeling, product architecting, concept generation, and team organization. A formal function representation is needed to support functional modeling, and a standardized set of function-related terminology leads to repeatable and meaningful results from such a representation. We refer to this representation as a functional basis; in this paper, we seek to reconcile …

A New Filtering Technique For A Class Of Nonlinear Systems, Ming Xin, S. N. Balakrishnan

Mechanical and Aerospace Engineering Faculty Research & Creative Works

In this paper, a new nonlinear filtering technique (θ-D filter) is presented. This filter is derived by constructing the dual of a new nonlinear regulator control technique, θ-D approximation which involves approximate solution to the Hamilton-Jacobi-Bellman equation. The structure of this filter is similar to the state dependent riccati equation filter (SDREF). However, this method does not need time-consuming online computation of the algebraic Riccati equation at each sample time compared with the SDREF. By manipulating the perturbation terms both the asymptotic stability and optimality properties can be obtained. A simple pendulum problem is investigated to demonstrate the effectiveness of …

Experimental Implementation Of Adaptive-Critic Based Infinite Time Optimal Neurocontrol For A Heat Diffusion System, Prashant Prabhat, S. N. Balakrishnan, Dwight C. Look

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Recently the synthesis methodology for the infinite time optimal neuro-controllers for PDE systems in the framework of adaptive-critic design has been developed. In this paper, first we model an experimental setup representing one dimensional heat diffusion problems. Then we synthesize and implement an adaptive-critic based neuro-controller for online temperature profile control of the experimental setup.

Accuracy And Efficiency In Fem Modeling Of Turbofan Acoustic Radiation, Eivind Listerud, Walter Eversman

Mechanical and Aerospace Engineering Faculty Research & Creative Works

It is shown that there is an increase in efficiency of acoustic radiation finite element modeling with the incorporation of cubic rather than quadratic serendipity elements. Cubic serendipity elements produce a given level of accuracy for acoustic pressure using a coarser mesh than required using quadratic elements, thus decreasing the CPU time needed for accurate modeling. These elements have been applied to the near field inlet and aft acoustic radiation models for a turbofan engine with the result of considerable reduction in the dimensionality of the problem without sacrificing accuracy. Visual observations of the gain in computational efficiency is supported …

Cfd Simulations Of Critical Components In Fuel Filling Systems, R. Banerjee, X. Bai, D. Pugh, Kakkattukuzhy M. Isaac, D. Klein, J. Edson, W. Breig, L. Oliver

Mechanical and Aerospace Engineering Faculty Research & Creative Works

A comprehensive study is reported on the dynamics of critical components in the refueling process for passenger cars and light trucks. Nozzle, filler pipe, recirculation tube, tank, and canister are investigated. CFD simulations are conducted for flow rates of 4 liters/min (lpm) to 80 lpm for gasoline and up to 120 lpm for diesel fuel. Tank pressure, identified as a critical parameter controlling flow performance, is measured and utilized as a boundary condition. Flow simulation in a carbon canister, accomplished by treating the adsorbing carbon as a porous medium, indicates pressure drops which are in good agreement with published experimental …

Proper Orthogonal Decomposition Based Optimal Control Design Of Heat Equation With Discrete Actuators Using Neural Networks, Radhakant Padhi, S. N. Balakrishnan

Mechanical and Aerospace Engineering Faculty Research & Creative Works

A new method is presented for the optimal control design of one-dimensional heat equation with the actuators being concentrated at discrete points in the spatial domain. This systematic methodology incorporates the advanced concept of proper orthogonal decomposition for the model reduction of distributed parameter systems. After deigning a set of problem-oriented basis functions an analogous optimal control problem in the lumped domain is formulated. The optimal control problem is then solved in the time domain, in a state feedback sense, following the philosophy of adaptive critic neural networks. The control solution is then mapped back to the spatial domain using …

A Quantitative Similarity Metric For Design-By-Analogy, Daniel A. Mcadams, Kristin L. Wood

Mechanical and Aerospace Engineering Faculty Research & Creative Works

During the design and development of new products, design engineers use many techniques to generate and define new and "good" concepts. Inherent in this search for solutions is the conscious and unconscious reliance on prior experience and knowledge, or design-by-analogy. In this paper, a quantitative metric for design-by-analogy is developed. This metric is based on the functional similarity of products. By using this product-similarity metric, designers are able to formalize and quantify design-by-analogy techniques during concept and layout design. The methods, as developed in this paper, allow a designer with limited experience to develop sophisticated solutions that enhance the overall …

Forensic Investigation Of Failed Mast Arms Of Traffic Signal Supported Structures, Genda Chen, Michael G. Barker, D. Scott Mackenzie, Christopher W. Ramsay, Joe Alderson, Lokeswarappa R. Dharani, Jiaqing Yu

Civil, Architectural and Environmental Engineering Faculty Research & Creative Works

In Missouri, 11 traffic signal mast arms fractured at the arm-post weld connection in 7 years. To reduce this fatigue failure, the Missouri Department of Transportation developed a fatigue-resistant weld profile that increases the weld leg and reduces the slope of the weld at the toe. This study investigated causes of the failed arms, compared performance of new and old weld profiles, and suggested retrofitting measures for further investigation. The scope included a metallurgical investigation of one failed field mast arm, laboratory fatigue testing of five prototype mast arms (two new and three old profiles), and laboratory failure analysis of …

A New Method For Suboptimal Control Of A Class Of Nonlinear Systems, Ming Xin, S. N. Balakrishnan

Mechanical and Aerospace Engineering Faculty Research & Creative Works

In this paper, a new nonlinear control synthesis technique (θ - D approximation) is presented. This approach achieves suboptimal solutions to nonlinear optimal control problems in the sense that it solves the Hamilton-Jacobi-Bellman (HJB) equation approximately by adding perturbations to the cost function. By manipulating the perturbation terms both semi-globally asymptotic stability and suboptimality properties can be obtained. The convergence and stability proofs are given. This method overcomes the large control for large initial states problem that occurs in some other Taylor expansion based methods. It does not need time-consuming online computations like the state dependent Riccati equation (SDRE) technique. …

Effect Of Polymer-Surface Mobility On Adhesion In Poly(Methyl Methacrylate)-Tape System, Bhavesh C. Gandhi, Frank D. Blum, Lokeswarappa R. Dharani

Chemistry Faculty Research & Creative Works

The interaction between two polymer layers, especially adhesion between them, plays an important role in polymer processing and other applications. Detailed knowledge of the molecular structure and dynamics of polymer interfaces, and how they relate to macroscopic mechanical properties, should help designers construct more functional systems. Unfortunately, there have been few studies where both molecular and macroscopic studies have been performed on similar systems. In previous studies from our group, we have probed the dynamics of poly(methyl acrylate) (PMA) and thermal behavior of poly(methyl methacrylate) (PMMA) on silica. These studies helped us paint a picture for strongly bound molecules on …

Supersonic Combustion And Mixing Characteristics Of Hydrocarbon Fuels In Screamjet Engines, Ahmed A. Taha

Mechanical & Aerospace Engineering Theses & Dissertations

The combustion characteristics of gaseous propane in supersonic airflow using the rearward-facing step that is swept inward from both end sides is studied. The effect of sweeping the step on the flow field features of propane combustion is investigated.

The study of the supersonic combustion of ethylene is carried out using different combustor configurations, different main fuel equivalence ratios, and different pilot fuel equivalence ratios.

The swept step shows the ability to hold the propane flame in the supersonic air stream without extinction. It was found that the side sweeping of the combustor exhibits the high temperature and combustion products …

Finite Element Modal Formulation For Panel Flutter At Hypersonic Speeds And Elevated Temperatures, Guangfeng Cheng

Mechanical & Aerospace Engineering Theses & Dissertations

A finite element time domain modal formulation for analyzing flutter behavior of aircraft surface panels in hypersonic airflow has been developed and presented for the first time. Von Karman large deflection plate theory is used for description of the structural nonlinearity and third order piston theory is employed to account for the aerodynamic nonlinearity. The thermal loadings of uniformly distributed temperature and temperature gradients across the panel thickness are incorporated into the finite element formulation. By applying the modal reduction technique, the number of governing equations of motion is reduced dramatically so that the computational time of direct numerical integration …

Active And Adaptive Flow Control Of Twin-Tail Buffet And Applications, Zhi Yang

Mechanical & Aerospace Engineering Theses & Dissertations

Modern fighter aircraft with dual vertical tails are operated at high angles of attack. The vortex generated by leading edge extension (LEX) breaks down before reaching the two vertical tails. The wake of highly unsteady, turbulent flow causes unbalanced broadband aerodynamic loading on the tails and may produce severe buffet on the tails and lead to tail fatigue failure.

Flow suction along the vortex cores (FSVC) is investigated as an active control method for tail-buffet alleviation. Suction tubes have been tilted at different angles to study the control effectiveness of suction tubes orientation. Flow field response, aerodynamic loading and aeroelastic …

Stanford Experience And Programs In Micro, Nano And Pico Satellites, Robert J. Twiggs

Robert "Bob" Twiggs STEM Education Collection

A PowerPoint Presentation created by Professor Bob Twiggs titled "Stanford Experience and Programs in Micro, Nano and Pico Satellites" presented at the JPL Workshop on December 14, 2001.

Air Vehicle Path Planning, Jeffrey M. Hebert

Theses and Dissertations

This dissertation explores optimal path planning for air vehicles. An air vehicle exposed to illumination by a tracking radar is considered and the problem of determining an optimal planar trajectory connecting two prespecified points is addressed. An analytic solution yielding the trajectory minimizing the received radar energy reflected from the target is derived using the Calculus of Variations. Additionally, the related problem of an air vehicle tracked by a passive sensor is also solved. Using the insights gained from the single air vehicle radar exposure minimization problem, a hierarchical cooperative control law is formulated to determine the optimal trajectories that …

Reduced Order Modeling For High Speed Flows With Moving Shocks, David J. Lucia

Theses and Dissertations

The use of Proper Orthogonal Decomposition (POD) for reduced order modeling (ROM) of fluid problems is extended to high-speed compressible fluid flows. The challenge in using POD for high-speed flows is presented by the presence of moving discontinuities in the flow field. To overcome these difficulties, a domain decomposition approach is developed that isolates the region containing the moving shock wave for special treatment. The domain decomposition implementation produces internal boundaries between the various domain sections. The domains are linked using optimization-based solvers which employ constraints to ensure smoothness in overlapping portions of the internal boundary. This approach is applied …

Acoustic Emission For Periodic Inspection Of Composite Pressure Vessels, Bao Rasebolai Mosinyi

Master's Theses - Daytona Beach

Cost savings can be achieved in a wide range of applications by replacing the current procedure for hydrostatic recertification of high-pressure composite gas cylinders with acoustic emission (AE) nondestructive testing. Advantages of AE recertification over the current hydrostatic method include: (1) no water contamination, since pressurization of the cylinders is done with air as opposed to water; (2) the risk of damage is decreased since the test pressure is reduced from 166% of design pressure to 110% of operating pressure; (3) the ability of acoustic emission to detect and locate flaws increases safety; and (4) the in-situ method will reduce …

World Wide Web Resources For Materials Science, Serge Abrate

Mechanical and Aerospace Engineering Faculty Research & Creative Works

The internet makes technical information readily available in ways that were unthinkable a few years ago. This article shows how the World Wide Web (the web) can be used in a Materials Science class to enrich the educational process. Strategies for finding and evaluating information and are discussed. © 2002 Wiley Periodicals, Inc.

Stanford Experience And Programs In Micro, Nano And Pico Satellites, Robert J. Twiggs

Robert "Bob" Twiggs STEM Education Collection

A PowerPoint Presentation created by Professor Bob Twiggs titled "Stanford Experience and Programs In Micro, Nano and Pico Satellites" oresented at the International Space & Microsystems Workshop on November 27, 2001.

Innovation In Space: University Programs, Robert J. Twiggs

Robert "Bob" Twiggs STEM Education Collection

A PowerPoint Presentation created by Professor Bob Twiggs titled "Innovation in Space: University Programs" on November 15, 2001.

Distributed Fault Tolerance In Optimal Interpolative Nets, Daniel J. Simon

Electrical and Computer Engineering Faculty Publications

The recursive training algorithm for the optimal interpolative (OI) classification network is extended to include distributed fault tolerance. The conventional OI Net learning algorithm leads to network weights that are nonoptimally distributed (in the sense of fault tolerance). Fault tolerance is becoming an increasingly important factor in hardware implementations of neural networks. But fault tolerance is often taken for granted in neural networks rather than being explicitly accounted for in the architecture or learning algorithm. In addition, when fault tolerance is considered, it is often accounted for using an unrealistic fault model (e.g., neurons that are stuck on or off …

Modeling Axisymmetric Optical Precision Piezoelectric Membranes, James W. Rogers Jr.

Theses and Dissertations

The US Department of Defense (DOD), as well as the National Aeronautics and Astronautics Administration (NASA) and the Jet Propulsion Laboratory (JPL) are interested in developing and deploying precise, compliant, light-weight, space-based structures. More specifically, the Air Force’s core competencies ‘Aerospace Superiority’ and ‘Information Superiority’ demand ever-increasing depth and breadth of capability. Whether used for energy transmission or optical reconnaissance, current launch restraints limit rigid space-based optical reflector size. To support this requirement, the Air Force Research Laboratory (AFRL) is developing a large space-based optical membrane telescope. Inflatable reflectors can conceptually break this barrier, but controlling such a compliant structure …

Evolution Of The Cubesat Concept, Robert J. Twiggs

Robert "Bob" Twiggs STEM Education Collection

A PowerPoint Presentation created by Professor Bob Twiggs titled "Evolution of the CubeSat Concept" from October 28, 2001.

Highly Innovative And Rapid Turn-Around Space Test Program, Robert J. Twiggs

Robert "Bob" Twiggs STEM Education Collection

A PowerPoint Presentation created by Professor Bob Twiggs titled "Highly Innovative and Rapid Turn-around Space Test Program" from October 23, 2001.

“Walk” Evolution Of The Cubesat Concept, Robert J. Twiggs

Robert "Bob" Twiggs STEM Education Collection

A PowerPoint Presentation created by Professor Bob Twiggs titled "Walk: Evolution of the CubeSat Concept" and presented at the Western Region NASA Space Grant Consortium on October 19, 2001.

Introducing Cooperative Learning Through A Faculty Instructional Development Program, Nikos J. Mourtos, Emily L. Allen

Faculty Publications

Cooperative Learning was officially introduced in the College of Engineering at San Jose State University in 1995 with a two-day workshop. The Faculty Instructional Development Program in the college maintains interest in the subjsect and provides support for instructors who use Cooperative Learning, through workshops and informal discussions (Conversations on Teaching). This paper discusses the effectiveness of the program in introducing, promoting, and implementing Cooperative Learning among the faculty and students in the college of engineering. A variety of performance criteria have been used in this assessment, some faculty-centered and some student-centered. The results indicate that although a relatively small …