Aerospace Engineering Commons^™

Development And Testing Of A Multiple Filter Approach For Precise Dgps Positioning And Carrier-Phase Ambiguity Resolution, Paul E. Henderson

Theses and Dissertations

The most precise relative positioning obtained using differential GPS depends on accurately determining carrier-phase integer ambiguities. To achieve high precision, many current static and kinematic algorithms use a floating-point solution until enough information becomes available to fix the carrier-phase ambiguities accurately. A mew method is presented that uses a multiple model Kalman filter to resolve the carrier-phase integer ambiguities. This method starts with the floating-point results, yet smoothly and rapidly attains the precision of the correct fixed-integer solution, eliminating the need to decide when to switch from the floating to the fixed-integer solution. This method is based on a theoretically …

Quality Initiatives In The Air Force Development Of Reusable Launch Vehicles, Charles S. Galbreath

Theses and Dissertations

This thesis identifies useful tools and techniques available to aid the Air Force development of a reusable launch vehicle (RLV). These tools are identified by comparing traits found within the Lean Aerospace Initiative, Six Sigma and systems engineering. While identified specifically for the RLV effort, these tools and techniques will be of use to many development programs. Historical perspectives of both RLV development efforts within the Air Force and origins of modern quality teachings are provided to establish a common foundation of knowledge, upon which, further analysis can be conducted. This thesis, also, summarizes the current RLV effort within the …

Turbine Blade Surface Roughness Effects On Shear Drag And Heat Transfer, Jess W. Drab

Theses and Dissertations

This work used scaled samples of actual turbine blade surfaces to characterize correlations between turbine surface roughness, friction coefficient, and convective heat transfer rate-parameters which affect an engine's efficiency and the blade's lifespan. For erosion/deposits, friction coefficients up to 250 times higher and convective heat transfer coefficients of up to 150 times higher were found when compared to a flat plate baseline. Other roughness types (pitting and fuel deposits) yielded less dramatic results. These results did not follow existing friction coefficient-to-heat transfer coefficient correlations, such as the Reynolds analogy. While these analytical and empirical correlations hold for flat plates, they …

Vibration Suppression Of A Rotationally Periodic Structure Using An Adaptive/Ppf Control Law, Mark J. Keller

Theses and Dissertations

For a compressor disk, effective vibration suppression requires broadband control, and the elimination of inter-blade coupling forces. Previous researchers achieved this using an active/passive piezoelectric shunt network. Unfortunately, optimal tuning of the shunt requires prior knowledge of the coupling strength, which is not well defined. This thesis uses an adaptive parameter estimator to eliminate the inter-blade coupling forces. In addition, the passive shunt is replaced with an analogous positive position feedback method. The resulting control law was used on a simulated four and eight bladed system. While substantial reductions in system response were achieved for the Adaptive/PPF control technique, the …

Prediction Of Pilot Induced Oscillations (Pio) Due To Activator Rate Limiting Using The Open-Loop Onset Point (Olop) Criterion, Gregory P. Gilbreath

Theses and Dissertations

Rate limiting has been a causal or contributing factor for Pilot Induced Oscillations (PIO). As part of the joint Air Force Institute of Technology/Test Pilot School (AFIT/TPS) program, an examination of the Open-Loop Onset Point (OLOP) criterion, developed by DLR German Aerospace, was conducted to see if it could predict PIO due to rate limiting and to evaluate its potential as a design tool. The criterion was applied to three previous flight test programs involving rate limiting. Findings from this analysis led to the HAVE OLOP flight test which was flown on the NF-16D Variable Stability In-flight Simulator Test Aircraft …

Modification Of Position And Attitude Determination Of A Test Article Through Photogrammetry To Account For Structural Deformation, Sean A. Krolikowski

Theses and Dissertations

This study improved the current method of position and attitude determination to account for structural deformation of the wind tunnel test article due to aerodynamic loading. To account for deformation, parabolic bending and linear twisting coefficients were added into the Levenberg-Marquardt multi-parameter solver. By accounting for deformation, the accuracy of position and attitude determination was greatly improved. This study also takes a qualitative look at the optimum number of wind tunnel cameras and model targets. Optimal configuration was found to be around 50 targets and 2 cameras offset by 90 degrees.

Air Vehicle Optimal Trajectories For Radar Exposure Minimization, Michael C. Novy

Theses and Dissertations

This study addresses the problem of analyzing the single vehicle path planning problem for radar exposure minimization. The calculus of Variations and optimal control are applied to formulate the cost function and numerical algorithms are used to solve for the optimal paths. Cost sensitivity to path length is analyzed for flight against one radar; a second radar is then included in the formulation and the optimal path for flight between the radars is found for cases of equal and unequal radar power. The costs of the optimal path, direct path, and Voronoi diagram-generated paths are compared. Results indicate low sensitivity …

Concept Exploration Of An Australian Indigenous Space Launch Capability, Anthony J. Rogers

Theses and Dissertations

This thesis explores the possibility of establishing an Australian indigenous space launch capability through developing and examining an Australian space launch program model. The model is based around launch site location, vehicle design, program duration, and the percentage Australian indigenous input into the program. The model was optimised in an effort maximise the benefits of such a capability, namely political prestige, security and in country technological base, while minimising the program's overall cost.

Phugoid Damping Control, Nicolas J. Schindeler

Theses and Dissertations

A novel phugoid damping control design methodology is developed, based on the use of wind axes and a point-mass aircraft model. The state variables are air speed, flight path angle, and heading angle, the control variables are thrust setting, angle of attack, bank angle, and sideslip angle, and the command signals are airspeed, flight path angle, and heading angle or heading rate. All the variables and parameters are nondimensionalized. A multivariable set point controller is developed which consists of: (1) a trim calculation-based nonlinear feed-forward control computer; thus, given a commanded new trim state (air speed, flight path angle, and …

The Development Of A Finite Element Program To Model High Cycle Fatigue In Isotropic Plates, William C. Shipman

Theses and Dissertations

As part of a joint AFRL/DAGSI turbine blade research effort, a computer program has been developed that uses a von Karman large-deflection two-dimensional finite element approximation to determine stress levels and patterns in isotropic thin plates. The dynamic loading of various plates has been carried out in order to model a high cycle fatigue situation. The research considered the various effects of mode shapes, resident frequency, non-linear cyclic effect, endurance limits, and stress variations within a high cycle fatigue environment. Two main initiatives were taken. First, a transient analysis tool was developed that calculates stress and displacement patterns over a …

Computational Investigation Of Aeromechanical Hcf Effects In A Compressor Rotor, Andrew L. White

Theses and Dissertations

High-Cycle Fatigue is a major problem facing the gas turbine industry today. It has been investigated by many researchers, using many different methods. Due to its highly complex nature, designers still do not have adequate tools to accurately predict the onset of high-cycle fatigue. A three-dimensional Navier-Stokes program was used to perform a study of the unsteady aerodynamics on a compressor rotor. The effect of aerodynamic detuning on the forced response of a rotor blade was compared to a baseline tuned rotor case. Detuning consisted of a ten percent decrease in circumferential spacing between alternate pairs of blades. The high-cycle …

Proactive Rideshare Opportunity Brokering Services (Probs), Robert J. Twiggs, Brian Horais, Charles Byvik

Robert "Bob" Twiggs STEM Education Collection

A PowerPoint Presentation created by Professors Bob Twiggs, Brian Horais, and Charles Byvik titled "Proactive Rideshare Opportunity Brokering Services (PROBS) presented at the 2001 IEEE Aerospace Conference on February 26, 2001.

Spacecraft Program, Robert J. Twiggs

Robert "Bob" Twiggs STEM Education Collection

A PowerPoint Presentation created by Professor Bob Twiggs titled "Spacecraft Program" from January 8, 2001.

Antarctic 2000: An Expedition To Prepare For Mars Missions, Robert J. Twiggs

Robert "Bob" Twiggs STEM Education Collection

A PowerPoint Presentation created by Professor Bob Twiggs titled "Antarctic 2000: An Expedition to Prepare for Mars Missions" from January 7, 2001.

Low-Latitude Auroras: The Magnetic Storm Of 14–15 May 1921, S. M. Silverman, E. W. Cliver

United States Air Force: Publications

We review solar/geophysical data relating to the great magnetic storm of 14–15 May 1921, with emphasis on observations of the low-latitude visual aurora. From the reports we have gathered for this event, the lowest geomagnetic latitude of de6nite overhead aurora (coronal form) was 40° and the lowest geomagnetic latitude from which auroras were observed on the poleward horizon in the northern hemisphere was 30°. For comparison, corresponding overhead/low-latitude values of 48°/32° and 41°/20° were reported for the great auroras on 28–29 August and 1–2 September 1859, respectively. However, for the 1921 event, there is a report of aurora from Apia, …

Cd-Rom Nutrient Analysis Database Assists Self-Monitering Behavior Of Active Duty Air Force Personnel Receiving Nutrient Counseling For Weight Loss, Jane E. Heetderks-Cox, Betty B. Alford, Carolyn M. Bednar, Cynthia J. Heiss, Lisa A. Tauai, Kimberly K. Edgren

United States Air Force: Publications

This study observed the effect of using a computerized vs. a manual method of self-monitoring among Air Force personnel receiving nutrition counseling for weight loss.

U.S. Air Force Long-Range Strike Aircraft White Paper, United States Air Force

United States Air Force: Publications

As a result of DoD transformation plans and recent operational experience (Air War Over Serbia and Operation ENDURING FREEDOM) portions of the 1999 U.S. Air Force White Paper on Long Range Bombers have become outmoded. In October 2001, the Secretary of the Air Force directed an updated Long-range Strike Aircraft White Paper incorporating our new defense planning guidance. This document provides an update to the 1999 White Paper and reflects current decisions concerning bomber force structure and basing. While modification plans remain largely intact, the focus has been refined to support the Global Strike Task Force concept.

Lab Fattening And Non-Invasive Estimates Of Body Composition In Deer Mice, Edward T. Unangst, Michael J. Blair, Matthew W. Granger, David W. Hale

United States Air Force: Publications

Total body electrical conductivity measurements and lipid composition were determined for the deer mouse (Peromyscus maniculatus) to derive species specific calibration equations for use with EM-SCAN estimates of lean and fat tissue. For each individual, total body electrical conductivity was measured by EM-SCAN, and actual lipid content was determined by chemical extraction. Then, using estimated and actual lipid values, separate calibration equations were generated for freshly captured (lean) and laboratory maintained (fat) individuals, and a combined equation was derived for all individuals. These equations were variable in the accuracy of lipid estimates; the lowest relative error estimate (percent …

Market Assessment Of Forward-Looking Turbulence Sensing Systems, Paul Kauffmann, Andres Sousa-Poza

Engineering Management & Systems Engineering Faculty Publications

[Executive Summary] This study examined the feasibility of the next generation of forward sensing turbulence systems for the Part 121 market segment: Enhanced X band radar, LIDAR, and a product that combines these first two technologies. Highlights of the findings include:

• On an annual basis, Part 121 carriers experience at least 567.8 turbulence related injury events that result in 687 minor flight attendant injuries, 38.4 serious flight attendant injuries, 119.5 minor passenger injuries, and 17.1 serious passenger injuries.
• The expected cost of turbulence injuries to airlines is $164,286 for a serious flight attendant injury, $25,000 for a minor flight attendant …

Multi -Mission Attitude Determination System For Balloon Flight, Liping Mo

Doctoral Dissertations

MADS (Multi-mission Attitude Determination System) is a new software package used to determine the attitude of instruments on a high-altitude balloon employed for scientific experiments. There is no existing system for the automated determination of the attitude of instruments in balloon experiments, so we have developed MADS to do the data analysis for balloon experiments to find the location of astrophysical sources such as gamma-ray or x-ray sources.

The two areas that required most work were modeling star trackers and modeling the motion of the balloon. Star trackers are used on satellites, but are far too expensive and sophisticated to …

Collegiate Aviation Research And Education Solutions To Critical Safety Issues, Brent D. Bowen, Uno Aviation Institute

Faculty Books and Monographs

UNOAI Report 2001-5

This document contains four papers concerning collegiate aviation research and education solutions to critical safety issues. “Panel Proposal Titled Collegiate Aviation Research and Education Solutions to Critical Safety Issues for the Tim Forte Collegiate Aviation Safety Symposium” (Brent Bowen) presents proposals for panels on the following topics: geographic north versus magnetic north to provide enhanced national airspace system safety; weather safety training for general aviation pilots through computer flight simulation; identification of human behavior and aircraft maintenance safety issues; disaster preparedness, emergency response, and curriculum development; the collegiate aviation emergency response checklist; and systemic initiatives in aviation …

Amplitude Modulated Droplet Formation In High Precision Solder Droplet Printing, Qingbin Liu, M. Orme, Ming-Chuan Leu

Mechanical and Aerospace Engineering Faculty Research & Creative Works

There are many methods used at present to apply solder to wafers, ceramics, laminate and flex circuit boards, and other substrates. Among these, high-precision solder droplet printing technology, which is noncontact, data driven, flexible and environmentally friendly, is a key enabling technology. This technology selectively deposits solder droplets only where required, and therefore needs no mask or secondary resist removal, uses materials more efficiently and creates less waste than other methods. Currently, continuous droplet formation from capillary streams is mainly achieved by application of the well-known Rayleigh instability in which a sinusoidal disturbance is applied to the stream, resulting in …

Robust State Dependent Riccati Equation Based Guidance Laws, S. N. Balakrishnan, Ming Xin

Mechanical and Aerospace Engineering Faculty Research & Creative Works

A robust state dependent Riccati equation based guidance/control is investigated in this study. In order to have a better design tool in terms of required interceptor accelerations, the target intercept geometry is formulated in a set of polar coordinates. With this formulation, we formulate a cost function with state dependent weights. In this study, we investigate the effects of such cost functions on the levels of interceptor accelerations. We also synthesize a neural network based extra controller to achieve the robustness in the presence of the target acceleration. In this manner, we will not need target acceleration estimation explicitly in …

Cubesat: The Development And Launch Support Infrastructure For Eighteen Different Satellite Customers On One Launch, Robert J. Twiggs, Jordi Puig-Suari, Clark Turner

Robert "Bob" Twiggs STEM Education Collection

An article written by Professors Bob Twiggs, Jordi Puig-Suari, and Clark Turner titled "CubeSat:  The Development and Launch Support Infrastructure for Eighteen Different Satellite Customers on One Launch" and published in 2001.

Bioexplorer Bus‐Low Cost Approach, Robert J. Twiggs, Seiji Kuroki

Robert "Bob" Twiggs STEM Education Collection

An article titled "BioExplorer Bus‐Low Cost Approach" by Professor Bob Twiggs and Seiji Kuroki from 200.

Proactive Rideshare Opportunity Brokering Services (Probs) For Secondary Payloads, Robert J. Twiggs, Brian Horais, Chuck Byvik

Robert "Bob" Twiggs STEM Education Collection

An article written by Bob Twiggs, Brian Horias, and Byvik titled "Proactive Rideshare Opportunity Brokering Services (PROBS) for Secondary Payloads" and published in 2001.

Gulfstream Aerospace Aircraft Static Position Utility, Mark Eugene Ray

College of Graduate Studies: Theses & Dissertations (1964–2006)

My research project implements a Java based utility developed for commercial application by Gulfstream Aerospace employees and customers to determine static position data of Gulfstream aircraft. The static position data includes aircraft attitude, nose and main landing gear loads and aircraft ground clearance data.

The previous methods used to obtain this data were a family of spreadsheets. The spreadsheet solution has proven to be awkward and inaccessible for providing the required data. Therefore, Gulfstream Aerospace Management approved the design and implementation of a new aircraft static position utility.

The new utility is identified as the Gulfstream Aircraft Static Position (GASP) …

Fatigue Assessment Of Traffic Signal Mast Arms Based On Field Test Data Under Natural Wind Gusts, Genda Chen, Jingning Wu, Jiaqing Yu, Lokeswarappa R. Dharani, Michael G. Barker

Civil, Architectural and Environmental Engineering Faculty Research & Creative Works

In recent years, several states including Missouri, Wyoming, California, and Texas experienced fracture failures of traffic signal mast arms. Almost all the failures are associated with the propagation of defects or cracks. It is therefore imperative to evaluate existing mast arms using a simple yet accurate procedure. A statistical methodology is proposed to predict the fatigue life of signal mast arm structures on the basis of field-measured strain data. The annual occurrence of various stress levels is determined using the historical wind speed data in the vicinity of a mast arm structure and the strain readings of the structure under …

Finite Element Analysis And Active Control For Nonlinear Flutter Of Composite Panels Under Yawed Supersonic Flow, Khaled Abdel-Motagaly

Mechanical & Aerospace Engineering Theses & Dissertations

A coupled structural-electrical modal finite element formulation for composite panels with integrated piezoelectric sensors and actuators is presented for nonlinear panel flutter suppression under yawed supersonic flow. The first-order shear deformation theory for laminated composite plates, the von Karman nonlinear strain-displacement relations for large deflection response, the linear piezoelectricity constitutive relations, and the first-order piston theory of aerodynamics are employed. Nonlinear equations of motion are derived using the three-node triangular MIN3 plate element. Additional electrical degrees of freedom are introduced to model piezoelectric sensors and actuators. The system equations of motion are transformed and reduced to a set of nonlinear …

An Integrated Risk Analysis Methodology In A Multidisciplinary Design Environment, Katrina R. Hampton

Engineering Management & Systems Engineering Theses & Dissertations

Design of complex, one-of-a-kind systems, such as space transportation systems, is characterized by high uncertainty and, consequently, high risk. It is necessary to account for these uncertainties in the design process to produce systems that are more reliable. Systems designed by including uncertainties and managing them, as well, are more robust and less prone to poor operations as a result of parameter variability.

The quantification, analysis and mitigation of uncertainties are challenging tasks as many systems lack historical data. In such an environment, risk or uncertainty quantification becomes subjective because input data is based on professional judgment. Additionally, there are …