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Articles 2401 - 2430 of 5700
Full-Text Articles in Engineering
Unintended Consequences: Potential Downsides Of The Air Force's Conversion To Biofuels, Mark N. Goltz, Charles A. Bleckmann, Charles M. Mackay, Khai Vuong, Jerrod P. Mccomb
Unintended Consequences: Potential Downsides Of The Air Force's Conversion To Biofuels, Mark N. Goltz, Charles A. Bleckmann, Charles M. Mackay, Khai Vuong, Jerrod P. Mccomb
Faculty Publications
The desire to reduce US dependence on foreign energy, ongoing environmental concerns, and the rising cost of petroleum have sparked significant development of greener alternative and renewable energy sources such as alcohol-based biofuels. To address these issues, the Department of Defense DOD has moved to diminish its reliance on petroleum for fueling aircraft and ground equipment. The US Air Force, in alignment with DOD objectives, has initiated several goals for reducing its use of energy: (1) decrease the use of petroleum-based fuel by 2 percent annually for the vehicle fleet, (2) increase the use of alternative fuel in motor vehicles …
A Taskable Space Vehicle: Realizing Cost Savings By Combining Orbital And Suborbital Flight, Thomas Co, Jonathan T. Black
A Taskable Space Vehicle: Realizing Cost Savings By Combining Orbital And Suborbital Flight, Thomas Co, Jonathan T. Black
Faculty Publications
The use of space gives the United States distinct advantages in any battlefield environment, but the high cost of space operations increasingly jeopardizes those advantages. Although the United States pioneered much of the current space technology, declining budgets for space research, development, and operations leave our legacy systems vulnerable to adversaries around the world. Other nations formerly incapable of space exploitation are quickly learning to counter US space technologies at surprisingly low costs. In order to reduce the expense of deploying and maintaining a robust space capability, the Department of Defense (DOD) must change the status quo in space operations …
Achieving The Air Force’S Energy Vision, Frederick G. Harmon, Richard D. Branam, Doral E. Sandlin
Achieving The Air Force’S Energy Vision, Frederick G. Harmon, Richard D. Branam, Doral E. Sandlin
Faculty Publications
The US Air Force is the largest consumer of energy in the federal government, spending 9 billion in 2008 to fuel aircraft and ground vehicles as well as provide energy to installations.1 In that same year, the Air Force s fuel bill of 7 billion amounted to more than half of the US government s total fuel cost.2 Because of the critical and central role that energy plays in completion of the Air Force’s mission, the secretary of the Air Force has developed an Air Force energy plan supported by three pillars Reduce Demand, Increase Supply, and Culture …
X-Hale: Designing The Atmospheric Surveillance Platforms Of The Future, Christopher M. Shearer
X-Hale: Designing The Atmospheric Surveillance Platforms Of The Future, Christopher M. Shearer
Faculty Publications
Imagine the benefits that battlefield commanders or intelligence analysts could derive from an airborne surveillance platform that would carry a 500-pound payload, operate above the range of small arms fire, remain on station for weeks or even years, cost much less than a satellite, and relocate around the globe to a new region of interest within a couple of weeks. Realizing this concept, known as a high-altitude, long-endurance HALE aircraft, is a 10-to-15-year goal of researchers at the Air Force Institute of Technology AFIT. In order to reach this goal, those researchers are following a developmental path similar to the …
Using Nanotechnology To Detect Nerve Agents, Mark N. Goltz, Dong-Shik Kim, Leeann Racz
Using Nanotechnology To Detect Nerve Agents, Mark N. Goltz, Dong-Shik Kim, Leeann Racz
Faculty Publications
Nanotechnology has opened a wide range of opportunities having potential impacts in areas as diverse as medicine and consumer products. In collaboration with researchers at the University of Toledo UT, Air Force Institute of Technology AFIT scientists are exploring the possibility of using a nanoscale organic matrix to detect organophosphate OP nerve agents. Current techniques for detecting OP compounds are expensive and time consuming. Developing a nanoscale organic matrix sensor would allow for direct, real-time sensing under field conditions. This article describes the science behind such a sensor and its possible applications. High-performance sensors are needed to protect Soldiers and …
Aerospike Rockets For Increased Space Launch Capability, Carl R. Hartsfield, Richard D. Branam, Joshua N. Hall, Joseph R. Simmons Iii
Aerospike Rockets For Increased Space Launch Capability, Carl R. Hartsfield, Richard D. Branam, Joshua N. Hall, Joseph R. Simmons Iii
Faculty Publications
The US Department of Defense (DOD) increasingly depends on space assets for everyday operations. Precision navigation; communications; and intelligence, surveillance, and reconnaissance satellites are highly leveraged space assets. The launch vehicles that place these satellites in orbit are a major limitation of current space systems. If higher-performing launch vehicles were available, many satellites could accommodate additional capabilities, whether in terms of more sensor channels, types of payloads, electrical power, or propellant for orbital maneuvering and station keeping.
E-10a Mc2a Systems Engineering Case Study, Air Force Center For Systems Engineering, William Albery
E-10a Mc2a Systems Engineering Case Study, Air Force Center For Systems Engineering, William Albery
AFIT Documents
No abstract provided.
Photogrammetric Measurement Of Recession Rates Of Low Temperature Ablators Subjected To High Speed Flow, David W. Callaway
Photogrammetric Measurement Of Recession Rates Of Low Temperature Ablators Subjected To High Speed Flow, David W. Callaway
Theses and Dissertations
This research advances a technique to simulate high temperature/high speed effects in a high speed/low temperature environment and to capture recession of the test article in three-dimensions. A method of fabricating dry ice test articles was developed, and the AFIT Mach 3 pressure-vacuum wind tunnel was used in combination with the dry ice test articles to collect three-dimensional ablation data for models of different shapes at stagnation pressures ranging from approximately 0.4 atm to 3 atm and stagnation temperatures equivalent to room temperature. High speed Schlieren photography was used for visualization, and the three dimensional shape change was quantified with …
Simulations For The Test Flight Of An Experimental Hale Aircraft, Brooke E. Kaszynski
Simulations For The Test Flight Of An Experimental Hale Aircraft, Brooke E. Kaszynski
Theses and Dissertations
Recent events, such as the crash of NASA's Helios aircraft during a test flight, show that more must be known about the nonlinear control of HALE aircraft. Shearer, Cesnik and their co-workers have developed a code that is a practical solution to the coupled nonlinear aeroelasticity and flight dynamics of very flexible aircraft called the University of Michigan's Nonlinear Aeroelastic Simulation Toolbox (UM/NAST). They are also in the process of developing a model HALE aircraft called X-HALE which will be used to validate this code experimentally. This research performs flight simulations with UM/NAST so as to make predictions about X-HALE's …
Study Of Varying Boundary Layer Height On Turret Flow Structures, Renato Jelic
Study Of Varying Boundary Layer Height On Turret Flow Structures, Renato Jelic
Theses and Dissertations
The Air Force Institute of Technology and the Air Force Research Labs are investigating flows over turrets which are commonly encountered in directed energy integrations with air vehicles. In this work, the computational study was performed using the NASA developed time-marching finite volume code OVERFLOW 2.2 to analyze the effect of boundary layer height on symmetrical and non-symmetrical turret geometries. The effects of aerodynamics yield to the aberration of the laser beam through two methods, aero-optical and aero-mechanical jitter. The analysis of the flow features, pressure fluctuations, density fluctuations, and forces and moments on the various geometries was conducted to …
Host-Based Systemic Network Obfuscation System For Windows, Kevin E. Huber
Host-Based Systemic Network Obfuscation System For Windows, Kevin E. Huber
Theses and Dissertations
Network traffic identifies the operating system and services of the host that created the traffic. Current obfuscation programs focus solely on the Transport and Internet layer protocols of the TCP/IP model. Few obfuscation programs were developed to run on a Windows operating system to provide host-based obfuscation. Systemic Network Obfuscation System (SNOS) was developed to provide a thorough obfuscation process for network traffic on the Windows operating system. SNOS modifies the protocols found at all layers of the TCP/IP model to effectively obfuscate the Windows operating system and services running on the host.
Coverage Of Continuous Regions In Euclidean Space Using Homogeneous Resources With Application To The Allocation Of The Phased Array Radar Systems, Kassandra M. Merritt
Coverage Of Continuous Regions In Euclidean Space Using Homogeneous Resources With Application To The Allocation Of The Phased Array Radar Systems, Kassandra M. Merritt
Theses and Dissertations
Air surveillance of United States territory is an essential Department of Defense function. In the event of an incoming aerial attack on North America, the DoD, Department of Homeland Security, and Federal Aviation Administration surveillance capabilities are critical to discovering and tracking the threat so that it can be eliminated. Many of the currently used surveillance radar will reach the end of their design life within ten to twenty years. By replacing the current radar network with a single integrated network of Multifunction Phased Array Radar (MPAR) units, surveillance capabilities can be enhanced and life cycle cost can be reduced. …
A Relay-Rover Differential Game, Youngdong Choi
A Relay-Rover Differential Game, Youngdong Choi
Theses and Dissertations
Guidance laws are developed to optimally position a relay Micro-UAV (MAV) to provide an operator at the base with real-time Intelligence, Surveillance, and Reconnaissance (ISR) by relaying communication and video signals when the rover MAV performing the ISR mission is out of radio contact range with the base. The ISR system is comprised of two MAVs, the Relay and the Rover, and a Base. The Relay strives to minimize the radio frequency (RF) power required for maintaining communications, while the Rover performs the ISR mission, which may maximize the required RF power. The optimal control of the Relay MAV entails …
Design And Characterization Of A Space Based Chromotomographic Hyperspectral Imaging Experiment, Jason D. Niederhauser
Design And Characterization Of A Space Based Chromotomographic Hyperspectral Imaging Experiment, Jason D. Niederhauser
Theses and Dissertations
This research focuses upon the design, analysis and characterization of several systems related to a spacebased chromotomographic experiment (CTEx), a hyperspectral imager, currently in development at the Air Force Institute of Technology. Three interrelated subject-areas were developed. The initial focal point was a generic, system-level mechanical layout and integration analysis of the space-based instrument. The scope of this work was intended to baseline the space-based system design in order to allow for further trade-space refinement and requirements development. Second, development of an iteration upon the ground-based version of CTEx was accomplished in an effort to support higher-fidelity field data-collection. This …
Process For Refining And Validating A Finite Element Model Of An Experimental High-Altitude, Long-Endurance (Hale) Aircraft, Nicholas A. Sinnokrak
Process For Refining And Validating A Finite Element Model Of An Experimental High-Altitude, Long-Endurance (Hale) Aircraft, Nicholas A. Sinnokrak
Theses and Dissertations
The work presented here focuses on finite element (FE) modeling of X-HALE, a test aircraft designed and built by the University of Michigan, in conjunction with the Air Force Institute of Technology (AFIT) and Air Force Research Laboratory (AFRL). This scaled vehicle is representative of high-altitude, long-endurance (HALE) aircraft and was designed to provide controlled aeroelastic and flight data. FE models of portions of the X-HALE wing structure were created and analysis results were compared against two separate laboratory static bending tests conducted on X-HALE wing sections. The process documented here should improve future efforts to refine FE models of …
Operational Characteristics Of A Rotating Detonation Engine Using Hydrogen And Air, Rachel M. Russo
Operational Characteristics Of A Rotating Detonation Engine Using Hydrogen And Air, Rachel M. Russo
Theses and Dissertations
Rotating detonation engines (RDE) are pressure gain combustion engines that have the potential for greater efficiency than traditional, constant pressure, deflagration engines. RDEs are smaller and mechanically simpler than pulsed detonation engines. A small diameter (3 in) engine was successfully run on hydrogen and air. Most of the tests were conducted using air with a slightly lower diluents percentage (77% nitrogen as opposed to 79% nitrogen). These tests provided the foundation for determining the operational space (mass flow rate and equivalence ratio) of the rotating detonation engine. From the tests conducted with the lower diluents air, the appropriate run conditions …
Carbon Nanotube Field Emission Arrays, Benjamin L. Crossley
Carbon Nanotube Field Emission Arrays, Benjamin L. Crossley
Theses and Dissertations
This effort exploits the unique physical and electrical characteristics of carbon nanotubes (CNTs) for field emission applications. Carbon nanotube field emission devices are designed, fabricated, and tested. Two reliable CNT synthesis methods, microwave plasma enhanced chemical vapor deposition (MPE-CVD) and thermal chemical vapor deposition (T-CVD), are developed. The physical properties of the resulting CNTs are analyzed using Raman spectroscopy and Scanning electron microscopy (SEM) and then tested for field emission performance. The T-CVD grown CNTs are shown to have fewer growth defects, but suffer from less process control making integration into devices difficult without further process development. Field emission testing …
Optical Flow-Based Odometry For Underground Tunnel Exploration, Terra Kier
Optical Flow-Based Odometry For Underground Tunnel Exploration, Terra Kier
Theses and Dissertations
As military operations in degraded or GPS-denied environments continue to increase in frequency and importance, there is an increased necessity to be able to determine precision location within these environments. Furthermore, authorities are finding a record number of tunnels along the U.S.-Mexico border; therefore, underground tunnel characterization is becoming a high priority for U.S. Homeland Security as well. This thesis investigates the performance of a new image registration technique based on a two camera optical- flow configuration using phase correlation techniques. These techniques differ from other image based navigation methods but present a viable alternative increasing autonomy and answering the …
Performance Analysis And Optimization Of The Winnow Secret Key Reconciliation Protocol, Kevin C. Lustic
Performance Analysis And Optimization Of The Winnow Secret Key Reconciliation Protocol, Kevin C. Lustic
Theses and Dissertations
Currently, private communications in public and government sectors rely on methods of cryptographic key distribution that will likely be rendered obsolete the moment a full-scale quantum computer is realized, or efficient classical methods of factoring are discovered. There are alternative methods for distributing secret key material in a post-quantum era. One example of a system capable of securely distributing cryptographic key material, known as Quantum Key Distribution (QKD), is secure against quantum factorization techniques as its security rests on generally accepted laws of quantum physics. QKD protocols typically include a phase called Error Reconciliation, a clear-text classical-channel discussion between legitimate …
Characterizing Cyclostationary Features Of Digital Modulated Signals With Empirical Measurements Using Spectral Correlation Function, Mujun Song
Theses and Dissertations
Signal detection is widely used in many applications. Some examples include Cognitive Radio (CR) and military intelligence. CRs use signal detection to sense spectral occupancy. Without guaranteed signal detection, a CR cannot reliably perform its role. Similarly, signal detection is the first step for garnering an opponent's information. Wireless signal detection can be performed using many different techniques. Some of the most popular include matched filters, energy detectors (which use measurements such as the Power Spectral Density (PSD) of the signal), and Cyclostationary Feature Detectors (CFD). Among these techniques, CFD can be viewed as a compromise technique, in that it …
Face Recognition Via Ensemble Sift Matching Of Uncorrelated Hyperspectral Bands And Spectral Pcts, Mohd Fairul Mohd-Zaid
Face Recognition Via Ensemble Sift Matching Of Uncorrelated Hyperspectral Bands And Spectral Pcts, Mohd Fairul Mohd-Zaid
Theses and Dissertations
Face recognition is not a new area of study, but facial recognition using through hyperspectral images is a somewhat new concept which is still in its infancy. Although the conventional method of face recognition using Red-Green-Blue (RGB) or grayscale images has been advanced over the last twenty years, these methods are still shown to have weak performance whenever there are variations or changes in lighting, pose, or temporal aspect of the subjects. A hyperspectral representation of an image captures more information that is available within a scene than a RGB image therefore it is beneficial to study the performance of …
Risks Associated With Federal Construction Projects, Krishna R. Surajbally
Risks Associated With Federal Construction Projects, Krishna R. Surajbally
Theses and Dissertations
The rise in terrorism, corporate espionage, cyber attacks, and federal fiscal constraints play an important role in the federal construction process. The risks associated with these occurrences are studied to aid in the risk management of the military construction process. This paper presents the status of research into these areas to identify how methods, policies, applications, and information obtained from case studies can be used by stakeholders to manage risk in the United States Air Force construction process. The author reviewed research on risk associated with four essential components of the military construction process – Critical Infrastructure, Information Technology, Contracts, …
Enterprise Requirements And Acquisition Model, David A. Leach, Chad T. Searle
Enterprise Requirements And Acquisition Model, David A. Leach, Chad T. Searle
Theses and Dissertations
In support of senior leadership emphasis on improving early systems engineering and analysis, the Enterprise Requirements and Acquisition Model (ERAM) is a quantitative discrete-event process simulation model that accounts for activities from the identification of a desired space capability early in the JCIDS process through Milestone C of the acquisition system resulting in a probabilistic schedule distribution for a given concept. This model of the DoD's space capability development process will provide valuable decision making information for Concept Characterization and Technical Descriptions referenced during Analysis of Alternatives. The research focused on identifying activities, assigning historical triangular distributions and probabilities at …
Solar Warning Architecture For Manned Missions To Mars, James S. Bohren, John K. Howard
Solar Warning Architecture For Manned Missions To Mars, James S. Bohren, John K. Howard
Theses and Dissertations
Solar radiation storms represent a dire threat to manned interplanetary space travel. Earth's current solar forecasting architecture is Earth-focused and insufficient to provide timely warnings to a manned mission to Mars, therefore a "best value" solar warning architecture must be identified. A total of 14 solar warning architectures were developed by varying 5 solar sensor locations, 2 processing locations, and 2 communications strategies. Using Satellite Tool Kit, performance of the candidate architectures in terms of Warning Time and Solar Coverage was quantified during a Mars mission scenario based on NASA's Design Reference Architecture 5.0. Cost of each candidate architecture was …
Spacecraft Demand Tasking And Skip Entry Responsive Maneuvers, Robert A. Bettinger
Spacecraft Demand Tasking And Skip Entry Responsive Maneuvers, Robert A. Bettinger
Theses and Dissertations
The purpose of this research was to parametrically investigate the viability of skip entry maneuvers as an alternative to vacuum-only maneuvers, and to identify whether skip entry maneuvers can extend spacecraft mission lifetime by limiting propellant expenditure through the exploitation of the aerodynamic interaction between the upper atmosphere and an example entry vehicle and remote-sensing orbital platform. Employing the X-37B Orbital Test Vehicle (OTV) and a notional satellite design as the example entry vehicles, the entry profile dynamics of a skip entry maneuver were characterized with varying trajectory initial conditions such as entry altitude, entry flight-path angle, and vehicle aerodynamics. …
Wolf Ant, Gilbert L. Peterson, Christopher M. Mayer, Kevin Cousin
Wolf Ant, Gilbert L. Peterson, Christopher M. Mayer, Kevin Cousin
Faculty Publications
Ant colony optimization (ACO) algorithms can generate quality solutions to combinatorial optimization problems. However, like many stochastic algorithms, the quality of solutions worsen as problem sizes grow. In an effort to increase performance, we added the variable step size off-policy hill-climbing algorithm called PDWoLF (Policy Dynamics Win or Learn Fast) to several ant colony algorithms: Ant System, Ant Colony System, Elitist-Ant System, Rank-based Ant System, and Max-Min Ant System. Easily integrated into each ACO algorithm, the PDWoLF component maintains a set of policies separate from the ant colony's pheromone. Similar to pheromone but with different update rules, the PDWoLF policies …
Ir Nonlinear Absorption Leading To Laser-Induced Damage In Ge & Gasb, Torrey J. Wagner, Matthew J. Bohn, Ronald A. Coutu Jr., L. P. Gonzales, J. M. Murray, K. L. Schepler, S. Guha
Ir Nonlinear Absorption Leading To Laser-Induced Damage In Ge & Gasb, Torrey J. Wagner, Matthew J. Bohn, Ronald A. Coutu Jr., L. P. Gonzales, J. M. Murray, K. L. Schepler, S. Guha
Faculty Publications
Using a simultaneous fitting technique to extract nonlinear absorption coefficients from data at two pulse widths, we measure two-photon and free-carrier absorption coefficients for Ge and GaSb at 2.05 and 2.5 μm for the first time. Results agreed well with published theory. Single-shot damage thresholds were also measured at 2.5 μm and agreed well with modeled thresholds using experimentally determined parameters including nonlinear absorption coefficients and temperature dependent linear absorption. The damage threshold for a single-layer Al2O3 anti-reflective coating on Ge was 55% or 35% lower than the uncoated threshold for ps or ns pulses, respectively. Wavelength-dependant …
Complementary Metal-Oxide Semiconductor-Compatible Detector Materials With Enhanced 1550 Nm Responsivity Via Sn-Doping Of Ge/Si(100), Richard T. Beeler, Jay Mathews, Mee-Yi Ryu, Yung-Kee Yeo, Jose Menendez, John Kouvetakis
Complementary Metal-Oxide Semiconductor-Compatible Detector Materials With Enhanced 1550 Nm Responsivity Via Sn-Doping Of Ge/Si(100), Richard T. Beeler, Jay Mathews, Mee-Yi Ryu, Yung-Kee Yeo, Jose Menendez, John Kouvetakis
Faculty Publications
Previously developed methods used to grow Ge1−ySny alloys on Si are extended to Sn concentrations in the 1019−1020 cm−3 range. These concentrations are shown to be sufficient to engineer large increases in the responsivity of detectors operating at 1550 nm. The dopant levels of Sn are incorporated at temperatures in the 370–390 °C range, yielding atomically smooth layers devoid of threading defects at high growth rates of 15–30 nm/min. These conditions are far more compatible with complementary metal-oxide semiconductor processing than the high growth and processing temperatures required to achieve the same …
Led Device Having Improved Light Output, Ronald S. Cok, Michael E. Miller
Led Device Having Improved Light Output, Ronald S. Cok, Michael E. Miller
AFIT Patents
A thin-film, white-light-emitting diode device includes a reflective, conductive thin-film structure and a semi-transparent, conductive thin-film structure. One or more thin-film layers are formed between the reflective and semi-transparent conductive thin-film structures to form two or more commonly-controlled microcavity structures. The thin-film layers emit white light in response to current provided by the conductive thin-film structure. Each of the two or more commonly-controlled microcavity structures has a different resonant frequency within one or more optical cavities and emits light with a smaller spectral range than the spectral range of the white-light-emitting thin-film layer(s). A combination of light emitted from the …
A-10 Thunderbolt Ii (Warthog) Systems Engineering Case Study, Air Force Center For Systems Engineering, David R. Jacques, Dennis D. Strouble
A-10 Thunderbolt Ii (Warthog) Systems Engineering Case Study, Air Force Center For Systems Engineering, David R. Jacques, Dennis D. Strouble
AFIT Documents
No abstract provided.