Aerospace Engineering Commons^™

Osculating Relative Orbit Elements Resulting From Chief Eccentricity And J2 Perturbing Forces, Joshuah A. Hess

Theses and Dissertations

Relative orbit elements (ROEs) based on a circular chief satellite orbit are erroneous when applied to a perturbed,non-circular reference orbit. In those situations, the ROEs will encounter geometric instability and drift. To counter this, a set of time-variant ROEs have been derived to describe the relative orbit for both the unperturbed, elliptical chief, and the perturbed, circular chief. A highly coupled relationship is found that describes the relative trajectory to higher accuracy when compared to numerical integration. To show the applicability of the ROEs to formation design, methods to initialize a stationary relative orbit are detailed and an algorithm for …

Revolutionizing Space Propulsion Through The Characterization Of Iodine As Fuel For Hall-Effect Thrusters, Adam C. Hillier

Theses and Dissertations

The demand for increased performance in space propulsion systems is higher than ever as missions are becoming more advanced. As the global supply of xenon depletes, missions demanding high thrust will require alternatives. The research presented here examines iodine as an alternate propellant. The propellant was successfully operated through a BHT-200 thruster in the T6 vacuum facility at Busek Co. Inc. A feed system for the iodine was developed for controlled thruster operation at varying conditions. An inverted pendulum was used to take thrust measurements. Thrust to power ratio, anode efficiency, and specific impulse were calculated. Iodine performance is compared …

Heat Transfer Experiments On A Pulse Detonation Driven Combustor, Nicholas C. Longo

Theses and Dissertations

Heat transfer experiments were conducted using a heat exchanger behind a pulse detonation combustor and a Garrett automotive turbocharger at the Air Force Research Lab (AFRL). The equivalence ratio and purge fraction were held at 1.0 and 0.9, respectively, while the frequency of operation was varied from 10 to 12 Hz in 1 Hz movements, and the fill fraction was varied from 0.5 to 0.8 in 0.1 increments. Temperature measurements were calculated using an energy balance allowing for the calculation of heat exchanger inlet enthalpy. The heat exchanger inlet enthalpy was estimated to be the exit enthalpy of the turbocharger …

Detonation Propagation Through Ducts In A Pulsed Detonation Engine, Jeffrey M. Nielsen

Theses and Dissertations

Development of a continuously operating pulsed detonation engine (PDE) without a high energy ignition system or a deflagration-to- detonation transition (DDT) device will increase engine efficiency, reduce cost, improve performance, and reduce weight. This report is a study of configurations that allow a consistent and predictable transition of a detonation from one detonation tube to second tube. The intent was, via visualization of detonation propagation through a cross-over tube, to develop a cross-over passage leading to minimization of energy losses and effective and repeatable tube-to-tube initiation. Detonation tube cross-over width, cross-over geometry and fuels were varied to determine their effect …

Two Dimensional Positioning And Heading Solution For Flying Vehicles Using A Line-Scanning Laser Radar (Ladar), Brady T. Christel

Theses and Dissertations

Emerging technology in small autonomous flying vehicles requires the systems to have a precise navigation solution in order to perform tasks. In many critical environments, such as indoors, GPS is unavailable necessitating the development of supplemental aiding sensors to determine precise position. This research investigates the use of a line scanning laser radar (LADAR) as a standalone two dimensional position and heading navigation solution and sets up the device for augmentation into existing navigation systems. A fast histogram correlation method is developed to operate in real-time on board the vehicle providing position and heading updates at a rate of 10 …

Image Dependent Relative Formation Navigation For Autonomous Aerial Refueling, James M. Howard

Theses and Dissertations

This research tests the feasibility, accuracy, and reliability of a predictive rendering and holistic comparison algorithm with use of an optical sensor to provide relative distance and position behind a lead or tanker aircraft. Using an accurate model of a tanker, an algorithm renders image(s) for comparison with actual collected images by a camera installed on the receiver aircraft. Based on this comparison, information used to create the rendered image(s) is used to provide the relative navigation solution required for autonomous air refueling. Given enough predicted images and processing time, this approach should reliably find an accurate solution. Building on …

Polarimetric Enhancements To Electro-Optical Aided Navigation Techniques, Jeremiah D. Johnson

Theses and Dissertations

Navigation in indoor and urban environments by small unmanned systems is a topic of interest for the Air Force. The Advanced Navigation Technology Center at the Air Force Institute of Technology is continually looking for novel approaches to navigation in GPS deprived environments. Inertial sensors have been coupled with image aided concepts, such as feature tracking, with good results. However, feature density in areas with large, flat, smooth surfaces tends to be low. Polarimetric sensors have been used for surface reconstruction, surface characterization and outdoor navigation. This thesis combines aspects of some of these algorithms along with a realistic, micro-facet …

Signals Of Opportunity Navigation Using Wi-Fi Signals, Wilfred E. Noel

Theses and Dissertations

Since GPS is generally limited to areas with clear sky view, additional methods of navigation are currently being explored. This thesis explores navigation using Signals of Opportunity(SoOP). The signals chosen for evaluation in this thesis are the common Internet IEEE 802.11a/g signals, or Wi-Fi. This thesis presents SoOP navigation based on cross-correlations of received data from multiple Wi-Fi stations. It shows the effectiveness of the methods using collected Wi-Fi signals in a real-world environment. By using simple statistical representations of collected data in large groups, or windows, cross-correlation calculations can produce timing offsets between simulated stations. The timing offsets, or …

Vision Aided Inertial Navigation System Augmented With A Coded Aperture, Jamie R. Morrison

Theses and Dissertations

Navigation through an indoor environment is a formidable challenge for an autonomous micro air vehicle. One solution is a vision aided inertial navigation system using depth-from-defocus to determine heading and depth to features in the scene. Depth-from-defocus uses a focal blur pattern to estimate depth. As depth increases, the observable change in the focal blur is generally reduced. Consequently, as the depth of a feature to be measured increases, the measurement performance decreases. The Fresnel zone plate, used as an aperture, introduces multiple focal planes. Interference between the multiple focal planes produce changes in the aperture that extend the depth …

Small Internal Combustion Engine Testing For A Hybrid-Electric Remotely-Piloted Aircraft, Isseyas H. Mengistu

Theses and Dissertations

Efficient operation of a hybrid-electric propulsion system (HEPS) powering a small remotely-piloted aircraft (RPA) requires that a controller have accurate and detailed engine and electric motor performance data. Many small internal combustion engines (ICEs) currently used on various small RPA were designed for use by the recreational hobbyist radio-control (R/C) aircraft market. Often, the manufacturers of these engines do not make accurate and reliable detailed engine performance data available for their engines. A dynamometer testing stand was assembled to test various small ICEs. These engines were tested with automotive unleaded gasoline (the manufacturer's recommended fuel) using the dynamometer setup. Torque, …

Sizing Analysis For Aircraft Utilizing Hybrid-Electronic Propulsion Systems, Matthew D. Rippl

Theses and Dissertations

A submerged inlet investigation, using flow control in the form of discrete blowing, examined proximity and jet directionality to improve compressor face uniformity. The flow control locations were at the head of the ramp and part way down the ramp, providing four configurations under examination. Laser Doppler velocimetry (LDV)measurements at the throat determined the effect of the flow control based on the statistical velocity measurements. Blowing at closer proximity to the throat and targeting the largest velocity deficit region provided the best results. The airspeed and inlet velocity simulated takeoff and landing conditions; velocities ranged from Mach 0.1-0.3 at the …

Conceptual Design Tool To Analyze Electrochemically-Powered Micro Air Vehicles, Douglas J. Pederson

Theses and Dissertations

A multi-fidelity conceptual design tool was developed to assess electrochemically-powered micro air vehicles(MAVs). The tool utilizes four areas of contributing analyses (CAs): aerodynamics, propulsion, power management, and power sources to determine the endurance duration of a given mission. The low-fidelity aerodynamic CA consisted of drag polar calculations and the high-level CA used a vortex theory code called Athena Vortex Lattice (AVL). The propulsion CA employed QPROP and a MATLAB code that used experimental propeller data and motor constants to predict propeller-motor combination performance for the low- and high-fidelity tracks, respectively. The power management CA determined the percentage of required power …

Flapping Wing Micro Air Vehicle Wing Manufacture And Force Testing, Nathanael J. Sladek

Theses and Dissertations

Numerous wing manufacturing techniques have been developed by various universities for research on Flapping Wing Micro Air Vehicles. Minimal attention though is given to repeatability of wing aerodynamics and dynamic response, which is crucial to avoid asymmetric flapping. Thus the focus of this research becomes twofold. First, repeatable wing manufacturing techniques are developed to ensure flapping wings have similar aerodynamic and dynamic characteristics. For this purpose, four wing designs were selected to not only test the aerodynamics of the different designs, but to also validate manufacturing techniques. The various wing designs are assessed using two methods: dynamic and aerodynamic data. …

High Frequency Direction Finding Using Structurally Integrated Antennas On A Large Airborne Platform, Clair F. Corbin

Theses and Dissertations

Estimating the angle of arrival (AOA) of a high frequency (HF) signal, 2-32 MHz, is challenging, especially if the antenna array is installed on a platform with dimensions on the order of one wavelength. Accurate AOA estimates are necessary for search and rescue operations and geolocating RF emitters of interest. This research examines the performance of a direction finding (DF) system using structurally integrated (SI) antennas installed on an airborne platform which allows the aircraft structure to become the receiving element. Two simulated DF systems are analyzed at 4 and 11 MHz. The relationship between the number of SI antennas …

Coupling Vanishing Point Tracking With Inertial Navigation To Estimate Attitude In A Structured Environment, Dayvid Prahl

Theses and Dissertations

This research aims to obtain accurate and stable estimates of a vehicle's attitude by coupling consumer-grade inertial and optical sensors. This goal is pursued by first modeling both inertial and optical sensors and then developing a technique for identifying vanishing points in perspective images of a structured environment. The inertial and optical processes are then coupled to enable each one to aid the other. The vanishing point measurements are combined with the inertial data in an extended Kalman filter to produce overall attitude estimates. This technique is experimentally demonstrated in an indoor corridor setting using a motion profile designed to …

Analysis Of Flow Migration In An Ultra-Compact Combustor, Brian T. Bohan

Theses and Dissertations

One of the major efforts for turbine engine research is to improve the thrust to weight of the system. One novel concept for accomplishing this is the use of an Ultra-Compact Combustor (UCC). The UCC attempts to shorten the overall combustion length (thereby reducing weight) by performing the combustion in the circumferential direction along the outside diameter of the core flowpath. One of the major benefits of this design is enhanced combustion due to the establishment of a high-g field in the circumferential cavity. AFIT and the Air Force Research Laboratory (AFRL) have been teamed for several years in understanding …

Repeatable Manufacture Of Wings For Flapping Wing Micro Air Vehicles Using Microelectromechanical System (Mems) Fabrication Techniques, David S. Dawson

Theses and Dissertations

While there have been great advances in the area of Flapping Wing Micro Air Vehicles (FWMAV), prototype parts have been constructed with the objective of scientific discovery and basic research. There has been little effort to make parts that could be consistently and repeatedly manufactured. Until recently, there has been little, if any, focus on methods that could be used and verified by subsequent researchers. It is herein proposed that Microelectromechanical System fabrication methods will provide a fast, cheap, and highly repeatable manufacturing method for the FWMAV wings. The wings manufactured to demonstrate this process, bio-inspired by the Manduca Sexta, …

Fixed-Wing Aircraft Combat Survivability Analysis For Operation Enduring Freedom And Operation Iraqi Freedom, Christopher L. Jerome

Theses and Dissertations

The primary tenet of the aircraft survivability discipline is threat definition. In order to deliver relevant capabilities and protection to the warfighter it is imperative; therefore, to provide timely, accurate, and actionable threat data to the survivability community. In an attempt to identify the evolution of aircraft threats in today's combat environment, an analysis of fixed-wing aircraft battle damage was conducted. This analysis reports battle damage incidents from OPERATIONS ENDURING FREEDOM (OEF) and IRAQI FREEDOM(OIF). Additionally, reported damage incidents were then validated by crosschecking aircraft maintenance records from this period to eliminate non-hostile fire data points. This revolutionary approach uncovered …

Notch Sensitivity Of Fatigue Behavior Of A Hi-Nicalon/Sic Ceramic Composite With An Oxidation Inhibited Matrix At 1200°C In Air And In Steam, Garrett M. Kurtz

Theses and Dissertations

The effects of holes on the fatigue behavior of an advanced Silicon Carbide/Silicon Carbide (SiC/SiC) ceramic matrix composite (CMC) was investigated at 1200°C in laboratory air and in steam environment. The composite consisted of an oxidation inhibited HyprSiC matrix reinforced with laminated Hi-Nicalon fibers woven in an eight-harness-satin weave (8HSW). Fiber preforms were coated with pyrolytic carbon (PyC) fiber coating with boron carbide overlay and were then densified with HyprSiC matrix via chemical vapor infiltration (CVI). Effects if center hole on tensile stress-strain behavior and tensile properties were evaluated at 1200°C. To assess the effect of holes on fatigue performance, …

Design Of Attitude Control Actuators For A Simulated Spacecraft, Christopher G. Mcchesney

Theses and Dissertations

The Air Force Institute of Technology's attitude dynamics simulator, SimSat, is used for hardware-in-the-loop validation of new satellite control algorithms. To provide the capability to test algorithms for control moment gyroscopes, SimSat needed a control moment gyroscope array. The goal of this research was to design, construct, test, and validate a control moment gyroscope array for SimSat. The array was required to interface with SimSat's existing structure, power supply, and electronics. The array was also required to meet maneuver specifications and disturbance rejection specifications. First, the array was designed with initial sizing estimates based on requirements and vehicle size. Next, …

Optimized Dual Expander Aerospike Rocket, Joshua N. Hall

Theses and Dissertations

Research at the Air Force Institute of Technology (AFIT) focused on designing a cryogenic dual-expander aerospike nozzle (DEAN) upper stage rocket engine to produce 50,000 pounds-force (222.4 kilo-Newtons) vacuum thrust, 464 seconds of vacuum specific impulse and a thrust-to-weight ratio of 106.5. The use of dual expander cycles improves engine reliability, maximizes efficiency, and eliminates some catastrophic failure modes. An upper stage engine with an aerospike nozzle is shorter and lighter than an equivalent performing conventional bell nozzle upper stage engine. Previous research focused on first developing a feasible closed DEAN design model and secondly expanding the model to support …

Starting Cansat – Where To Now?, Robert J. Twiggs

Robert "Bob" Twiggs STEM Education Collection

A PowerPoint presentation created by Professor Bob Twiggs titled "Starting CanSat – Where to Now?" from March 8, 2011.

Test Case Series 1 (Overview Of Intercalibration Results: A Model Comparison), Thermal Performance Database Team

Ablation Workshop: Code Comparison

Presentation Overview:

• Comparison of model results
• All comparisons (plots) are percent difference from FIAT reference model

Overview Of Roughness And Blowing Effects In Flows Over Ablating Surfaces, Adam Amar, Charles Powars

Ablation Workshop

The scope of this session includes ablation effects on surface roughness and surface roughness effects on ablation. Ablation involves blowing, and so we address blowing including combined roughness and blowing effects. The two distinct types of ablating material surface roughness are defined with examples: 1) roughness related to the material inhomogeneity, and 2) roughness induced by turbulent flow that appears to be unrelated to material inhomogeneties.

Existing approaches for modeling ablative material surface roughness and blowing effects are overviewed. These range from empirical “augmentation factor” correlations to high-fidelity simulations of flow-surface interactions using modern CFD techniques. For models requiring input …

Gsi Modeling Overview: Requirements For Macroscopic Gas/Surface Interaction Coupling To Cfd Codes, Matthew Maclean, Jochen Marschall

Ablation Workshop

An overview is presented of a generalized finite-rate surface chemistry model that has been developed for gas/surface interaction coupling to the Data-Parallel Line-Relaxation (DPLR) code. Species from the gaseous environment are allowed to interact with species adsorbed onto one or more phase of a surface and with one or more phases of a bulk thermal protection system through an arbitrary number of finite-rate reactions. The reactions may include types such as adsorption, desorption, Eley-Rideal recombination, Langmuir-Hinschelwood recombination, partial or total dissociative adsorption, oxidation, reduction, sublimation, or condensation where forward and reverse rates are constrained by thermodynamics. A simple pyrolysis model …

High Enthalpy Ablation Testing At Dlr Cologne, Bunkard Esser, A. Gülhan, U. Koch

Ablation Workshop

Testing thermal protection capabilities of ablative materials is one of the main working areas of DLR’s arc heated facilities LBK in Cologne. Work on this particular topic has been intensified about five years ago with the following major focus points:

• Significant improvement of the facilities testing capabilities with respect to cold wall heat flux rates and stagnation pressure.
• Ablation testing in Martian atmosphere.
• Influence of dust particle erosion on ablation.

Nitric Oxide Plif Measurements In The Hypersonic Materials Environmental Test System (Hymets), Paul M. Danehy

Ablation Workshop

A nonintrusive laser-based measurement system has been applied for the first time in the HYMETS (Hypersonic Materials Environmental Test System) 400 kW arc-heated wind tunnel at NASA Langley Research Center. Planar laser-induced fluorescence of naturally occurring nitric oxide (NO) has been used to obtain instantaneous flow visualization images, and to make both radial and axial velocity measurements. Results are presented at selected facility run conditions, including some in simulated Earth atmosphere (75% nitrogen, 20% oxygen, 5% argon) and others in simulated Martian atmosphere (71% carbon dioxide, 24% nitrogen, 5% argon), for bulk enthalpies ranging from 6.5 MJ/kg to 18.4 MJ/kg. …

Experimental Data Need For High-Fidelity Material-Response Models, Jean R. Lachaud, Ioana Cozmuta, Nagi N. Mansour

Ablation Workshop

Several high-fidelity material-response models are being developed by the hypersonic community. These models require, in addition to the input parameters traditionally used in the state-of-the-art material-response codes, data not currently available - at least in the open literature. The presentations in the session will describe both state-of-the-art experimental techniques and innovative methods in support of model development and data acquisition for high-fidelity models.

Test Case Series 1, Jean R. Lachaud, Alexandre Martin, Ioana Cozmuta, Bernard Laub

Ablation Workshop: Code Comparison

A simple one-dimensional test case is defined for the purpose of inter-code comparison. This year the focus is set on in-depth physics and chemistry. Material properties, boundary conditions, and output format are provided.

Integration Of Aeroservoelastic Properties Into The Nasa Dryden F/A-18 Simulator Using Flight Data From The Active Aeroelastic Wing Program, Alexander Wong Chin

Master's Theses

Aircraft structures have varying stiffness levels making them flexible. Consequently, this elastic property becomes increasingly important at high speeds affecting the flight dynamics of the aircraft.  In high speed aircraft such as the F/A-18, elastic structural properties must be accounted for to ensure confidence in predicted flight dynamics in order to avoid adverse aeroelastic phenomena throughout flight.

Data from the F/A-18 Active Aeroelastic Wing (AAW) program was used to create aeroservoelastic (ASE) models at varying flight conditions. The discretized ASE models were integrated into the NASA Dryden F/A-18 simulator in parallel with the traditional 6-DOF (degrees-of-freedom) flight dynamics calculations to …