Engineering Commons^™

Grating Lobe Reduction In Aperiodic Linear Arrays Of Physically Large Antennas, William C. Barott, Paul G. Steffes

Publications

We present performance bounds obtained from the optimization of the sidelobe levels of aperiodic linear arrays. The antennas comprising these arrays are large compared to the distance between neighboring antennas, a case not addressed in previously published work. This optimization is performed in pattern-space and is applicable over a wide range of scan angles. We show that grating lobes can be suppressed even when the elemental antennas are several wavelengths in size, provided that the ratio of the antenna size to the average spacing between the antenna center-points does not exceed 80%.

Avoiding Overrun Accidents On Contaminated Runways, Nihad E. Daidzic

Aviation Department Publications

No abstract provided.

Project: F.U.N.B.O.E. (Follow-Up Nucleate Boiling On-Flight Experiment), Getaway Special Team 2009

Education and Outreach

No abstract provided.

Shock Effects On Delta Wing Vortex Breakdown, Lucy A. Schiavetta, Okko J. Boelens, Simone Crippa, Russell M. Cummings, Willy Fritz, Ken J. Badcock

Aerospace Engineering

It has been observed that delta wings placed in a transonic freestream can experience a sudden movement of the vortex breakdown location as the angle of incidence is increased. The chapter reports on the use Computational Fluid Dynamics (CFD) to examine this behaviour in detail. The study shows that a shock-vortex interaction is responsible. The balance of the vortex strength and axial flow, and the shock strength, is examined to provide an explanation of the sensitivity of the breakdown location. Limited experimental data is available to supplement the CFD results in certain key respects, and the ideal synergy between CFD …

Numerical Solutions For The Cawapi Configuration On Unstructured Grids At Usafa, United States, Scott A. Morton, David R. Mcdaniel, Russell M. Cummings

Aerospace Engineering

No abstract provided.

Numerical Solutions For The Vfe-2 Configuration On Unstructured Grids At Usafa, United States, Russell M. Cummings, Andreas Schϋtte

Aerospace Engineering

The numerical simulation of the flow for the VFE-2 configuration with rounded leading edges is presented. For the numerical simulation the Cobalt Code was used, which uses a cell-centered unstructured hybrid mesh approach. Several numerical results are presented for the steady RANS equations as well as for DES and DDES hybrid approaches. Within this paper the focus is related to the dual primary vortex flow topology, especially the sensitivity of the flow to angle of attack and Reynolds number effects. Reasonable results are obtained with both steady RANS and SA-DDES simulations. The results are compared and verified by experimental data, …

Lessons Learned From The Numerical Investigations On The Vfe-2 Configuration, Willy Fritz, Russell M. Cummings

Aerospace Engineering

The Second International Vortex Flow Experiment provided a variety of experimental data for a 65° delta wing with sharp and blunt/rounded leading edges. Flow measurements including forces and moments, surface pressures, Pressure Sensitive Paint measurements, and off-surface flow variables from Particle Image Velocimetry were made available for comparisons with computational simulations. A number of test cases were chosen for simulation by seven numerical groups, and a summary of their results is presented here. The ability of computational fluid dynamics to predict such flow features as the dual primary vortex system found on the blunt leading edge configuration and a shock/vortex …

Flightlines, Vol. 17, No. 1, Jeffrey A. Johnson

Flightlines Newsletter

No abstract provided.

Sixth Grade Lesson Plan: Heat Moves, Getaway Special Team 2009

Education and Outreach

No abstract provided.

Third Grade Lesson Plan: Where Does Heat Come From?, Getaway Special Team 2009

Education and Outreach

No abstract provided.

Reinforcement-Learning-Based Output-Feedback Control Of Nonstrict Nonlinear Discrete-Time Systems With Application To Engine Emission Control, Peter Shih, Brian C. Kaul, Jagannathan Sarangapani, J. A. Drallmeier

Electrical and Computer Engineering Faculty Research & Creative Works

A novel reinforcement-learning-based output adaptive neural network (NN) controller, which is also referred to as the adaptive-critic NN controller, is developed to deliver the desired tracking performance for a class of nonlinear discrete-time systems expressed in nonstrict feedback form in the presence of bounded and unknown disturbances. The adaptive-critic NN controller consists of an observer, a critic, and two action NNs. The observer estimates the states and output, and the two action NNs provide virtual and actual control inputs to the nonlinear discrete-time system. The critic approximates a certain strategic utility function, and the action NNs minimize the strategic utility …

Avoiding Aircraft Icing Accidents, Nihad E. Daidzic

Aviation Department Publications

No abstract provided.

Fifth Grade Lesson Plan: Solid, Liquid, And Gas, Getaway Special Team 2009

Education and Outreach

No abstract provided.

Cost-Benefit Analysis Of Error Reduction For Complex Systems, Robert A. Mcdonald

Aerospace Engineering

The cost-benefit tradeoff of analysis fidelity in complex systems analysis has been posed as an optimization problem providing quantitative guidance for investment in improving analysis. A nonlinear constrained optimizer to solve this problem has been integrated into an error tradeoff environment providing an intuitive tool for the decision maker to consider investment in fidelity at the same time as design decisions are considered. An example demonstrates the efficacy of the improved interface to enable fidelity improvement investment decisions.

Multidisciplinary Design Optimization Of An Extreme Aspect Ration Hale Uav, Bryan Morrisey, Robert A. Mcdonald

Aerospace Engineering

Development of High Altitude Long Endurance (HALE) aircraft systems is part of a vision for a low cost communications/surveillance capability. Applications of a multi payload aircraft operating for extended periods at stratospheric altitudes span military and civil genres and support battlefield operations, communications, atmospheric or agricultural monitoring, surveillance, and other disciplines that may currently require satellite-based infrastructure. The central goal of this research was the development of a multidisciplinary tool for analysis, design, and optimization of HALE UAVs, facilitating the study of a novel configuration concept. Applying design ideas stemming from a unique WWII-era project, a "pinned wing" HALE aircraft …

Heavy-Fueled Intermittent Ignition Engines: Technical Issues, Jeffrey Arthur Schneider, Timothy Wilson, Christopher Griffis, Peter Pierpont

Publications

This report contains an overview of the technology and engineering issues with nonturbine heavy-fueled engines for general aviation aircraft and Unmanned Aircraft Systems. In recent years, interest in these types of engines has grown, partly due to the cost, safety, and worldwide availability of gasoline fuels. Within 3 to 5 years, up to five engines will seek Federal Aviation Administration certification as heavy-fuel powerplants. Although there has been some progress, there is no universal standard for certification of these engines (under Title 14 Code of Federal Regulations (CFR) Part 33), or their installation into normal category fixed-wing aircraft or rotorcraft …

Unmanned Aircraft System Propulsion Systems Technology Survey, Christopher Griffis, Timothy Wilson, Jeffrey Schneider, Peter Pierpont

Publications

This technology survey is an investigation of various propulsion systems used in Unmanned Aircraft Systems (UAS). Discussed are existing and near-future propulsion mechanisms of UAS, such as reciprocating piston engines, Wankel rotary engines, gas turbine engines, rocket-powered systems, electric motors, and battery-based systems. Also discussed are systems that use proton exchange membrane fuel cells, photovoltaics, ultracapacitors, and propellers. Each system is described in reference to a larger conceptual framework, with instances and profiles of existing UAS employing the system being described. Advantages and disadvantages of each type of propulsion system are identified along with associated technical issues and their respective …

Phase Change Mechanisms During Femtosecond Laser Pulse Train Ablation Of Nickel Thin Films, Xin Li, Lan Jiang, Hai-Lung Tsai

Mechanical and Aerospace Engineering Faculty Research & Creative Works

The mechanisms of nickel thin films irradiated by femtosecond laser pulse trains are studied by a model using molecular dynamics simulations and two-temperature model. It is found that the pulse train technology can change energy transport and corresponding phase change processes. Compared with single pulse ablation at the same total fluence, the pulse trains lead to (1) lower ablation rate with more and smaller uniform nanoparticles, (2) higher film surface temperatures and longer thermalization time, (3) much lower electron thermal conductivity that can further control heat-affected zone, (4) significantly smaller film compressive stresses and tensile stresses which reduce microcracks, and …

Avoiding Veer-Off Accidents On Contaminated Runways, Nihad E. Daidzic

Aviation Department Publications

No abstract provided.

Evaluation Of Direct Diode Laser Deposited Stainless Steel 316l On 4340 Steel Substrate For Aircraft Landing Gear Application, Tian Fu, Todd E. Sparks, Frank W. Liou, Joseph William Newkirk, Zhiqiang Fan, Syamala Rani Pulugurtha, Jianzhong Ruan, Hsin-Nan Chou

Mechanical and Aerospace Engineering Faculty Research & Creative Works

300M steel is used extensively for aircraft landing gears because of its high strength, ductility and toughness. However, like other high-strength steels, 300M steel is vulnerable to corrosion fatigue and stress corrosion cracking, which can lead to catastrophic consequences in the landing gear. Stainless steels offer a combination of corrosion, wear, and fatigue properties. But for an aircraft landing gear application a higher surface hardness is required. A laser cladding process with fast heating and cooling rates can improve the surface hardness. AISI 4340 steel is used as a lower cost alternative to 300M due to its similar composition. In …

Developing Abrasion Test Standards For Evaluating Lunar Construction Materials, Ryan L. Kobrick, David M. Klaus, Kenneth W. Street

Publications

Operational issues encountered by Apollo astronauts relating to lunar dust were catalogued, including material abrasion that resulted in scratches and wear on spacesuit components, ultimately impacting visibility, joint mobility and pressure retention. Standard methods are being developed to measure abrasive wear on candidate construction materials to be used for spacesuits, spacecraft, and robotics. Calibration tests were conducted using a standard diamond stylus scratch tip on the common spacecraft structure aluminum, Al 6061-T6. Custom tips were fabricated from terrestrial counterparts of lunar minerals for scratching Al 6061-T6 and comparing to standard diamond scratches. Considerations are offered for how to apply standards …

Access Mars: Assessing Cave Capabilities Establishing Specific Solutions: Final Report, Abdul Mohsen Al Husseini, Luis Alvarez Sanchez, Konstantinos Antonakopoulos, Jeffrey (Johannes) Apeldoorn, Kenneth Lowell Ashford Jr., Kutay Deniz Atabay, Sara Langston, Et Al.

Publications

The human race has evolved, grown and expanded through the exploration of Earth. After initial steps on the Moon, our next challenge is to explore the solar system. Mars shows potential for both scientific discovery and future human settlement, and so is a prime candidate for the next leap of human exploration. Such a bold endeavor will be a driver for an unprecedented worldwide cooperative effort and the catalyst for a new era of international, intercultural and interdisciplinary human relations. Scientific and technological progress will also accelerate as mankind is ushered into a new era of space exploration.

Currently proposed …

Comparison Of Overset Grid And Grid Deformation Techniques Applied To 2-Dimensional Naca Airfoils, Charles M. Hoke, Robert K. Decker, Russell M. Cummings, David R. Mcdaniel, Scott A. Morton

Aerospace Engineering

This paper documents a comparison of overset grid and grid deformation schemes applied to flapped and non-flapped NACA airfoil configurations in order to determine the relative accuracy and computational efficiency of each method. This study is part of a larger effort to use computational fluid dynamics to perform moving control surface calculations. Three different cases, using both overset and deformed grids, are considered, including: a) lift and moment comparison of a quasi-steady, non-flapped 0012 airfoil, b) lift and moment comparison of a dynamically pitching non-flapped 0012 airfoil, and c) lift comparison of a dynamic pitching and oscillating flapped 0012 airfoil. …

Application Of Volterra Functions To X-31 Aircraft Model Motion, United States Air Force Academy, Russell M. Cummings

Aerospace Engineering

Recent advances towards an efficient computational method for accurately determining the stability and control characteristics of an aircraft are discussed and critiqued. The present approach with greatest promise is to reduce the number of high-fidelity CFD simulations by using Volterra functions Reduced Order Modeling. This type of reduced order model is a predictive model which has a unique training maneuver -a unit impulse. The advantage of such an approach is the fast prediction of the aerodynamic characteristics of an aircraft. This article presents the results of application of the Volterra functions ROM for prediction of linear movement of a 2D …

A New State Observer And Flight Control Of Highly Maneuverable Aircraft, S. N. Balakrishnan, Ming Xin

Mechanical and Aerospace Engineering Faculty Research & Creative Works

In this paper, a new nonlinear observer (θ-D observer) is proposed to estimate the feedback states for optimal control of a highly maneuverable aircraft. This observer is derived by constructing the dual of a recently developed nonlinear optimal control technique-known as the θ-D technique. The θ-D optimal control approach provides an approximate closed-form solution to the Hamilton-Jacobi-Bellman (HJB) equation. An optimal flight controller using this technique is designed for a highly maneuverable aircraft operating at high angle of attack where the θ-D observer is employed to estimate the states for feedback. The structure of this observer is similar to the …

Chilling Out In The Sim: The Need For Icing Training., Nihad E. Daidzic

Aviation Department Publications

No abstract provided.

A Microfabricated Segmented-Involute-Foil Regenerator For Enhancing Reliability And Performance Of Stirling Engines: Phase Iii Final Report For The Radioisotope Power Conversion Technology Nra Contract Nas3-03124, Mounir B. Ibrahim, David Gedeon, Gary Wood, Jeffrey Mclean

Mechanical Engineering Faculty Publications

Under Phase III of NASA Research Announcement contract NAS3-03124, a prototype nickel segmented-involute-foil regenerator was microfabricated and tested in a Sunpower Frequency-Test-Bed (FTB) Stirling convertor. The team for this effort consisted of Cleveland State University, Gedeon Associates, Sunpower Inc. and International Mezzo Technologies. Testing in the FTB convertor produced about the same efficiency as testing with the original random-fiber regenerator. But the high thermal conductivity of the prototype nickel regenerator was responsible for a significant performance degradation. An efficiency improvement (by a 1.04 factor, according to computer predictions) could have been achieved if the regenerator was made from a low-conductivity …

Are Wireless Sensors Feasible For Aircraft?, Thomas Yang, Jianhua Liu, Ilteris Demirkiran

Department of Electrical Engineering and Computer Science - Daytona Beach

Wireless communications is a preferred way of data transmission in many aerospace applications. Replacing some aircraft sensor wiring with wireless communications is a highly desirable but challenging transformation. The related sensors are referred to as aerospace wireless sensors (AWSs). This replacement can lower the weight of aircraft wiring, improve the overall safety of aircraft, simplify the design of aircraft structures, and lower the sensor installation and maintenance cost. The major concern for using AWSs is the potential negative effects on overall reliability and safety of aircraft. In this paper, the feasibility of using AWSs is discussed. In particular, the appropriate …

A Technology Survey Of Emergency Recovery And Flight Termination Systems For Uas, Richard Stansbury, Wesley Tanis, Timothy Wilson

Publications

For safe flight in the National Airspace System (NAS), either under the current interim rules or under anticipated longer-term regulatory guidelines facilitating unmanned aircraft system (UAS) access to the NAS, the UAS must incorporate technologies and flight procedures to ensure that neither people nor property in the air, on the ground, or on or in the water are endangered by the failure of an onboard component, by inappropriate unmanned aircraft (UA) response to pilot commands, or by inadvertent entry by the UA into prohibited airspace. The aircraft must be equipped with emergency recovery (ER) procedures and technologies that ensure that …

Flightlines, Vol. 16, No. 2, Jeffrey A. Johnson

Flightlines Newsletter

No abstract provided.