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Articles 1 - 30 of 52
Full-Text Articles in Engineering
Spacex: Breaking The Barrier To The Space Launch Vehicle Industry, Matthew M. Liskowcyz
Spacex: Breaking The Barrier To The Space Launch Vehicle Industry, Matthew M. Liskowcyz
Theses and Dissertations
The Space Launch Vehicle (SLV) industry has been around for a long time, but few companies have managed to enter this industry. SpaceX was founded only 10 years ago, but it has managed to become a leader in the U.S. industry and a dominant player worldwide. The purpose of this thesis research is to discover what it took for SpaceX to break into this tightly controlled industry. A qualitative analysis was performed to compare SpaceX to companies that overcame the barriers of entry for their respective industries. SpaceX, like FedEx, could implement a unique technique to the industry and find …
Space Qualification Testing Of A Deployable Shape Memory Alloy Cubesat Antenna, Carl L. Kobza
Space Qualification Testing Of A Deployable Shape Memory Alloy Cubesat Antenna, Carl L. Kobza
Theses and Dissertations
Increasingly capable CubeSat missions require antenna with improved Radio Frequency performance over the traditional CubeSat antennas. Deployable quadrifilar helical antennas (QHA) enable an acceptable stowing volume and deploy to provide increased gain and bandwidth over traditional patch and dipole antennas. Extensive ground testing is required to ensure the antenna is space qualified and to characterize the antenna deployment in the space environment. AFIT requires a QHA to perform a future CubeSat geolocation mission and contracted Helical Communication Technologies (HCT) to design and manufacture a Shape Memory Alloy (SMA) L-band deployable QHA. Vibration, thermal vacuum, laser vibrometer, and Voltage Standing Wave …
Adaptive Estimation And Heuristic Optimization Of Nonlinear Spacecraft Attitude Dynamics, Joshuah A. Hess
Adaptive Estimation And Heuristic Optimization Of Nonlinear Spacecraft Attitude Dynamics, Joshuah A. Hess
Theses and Dissertations
For spacecraft conducting on-orbit operations, changes to the structure of the spacecraft are not uncommon. These planned or unanticipated changes in inertia properties couple with the spacecraft's attitude dynamics and typically require estimation. For systems with time-varying inertia parameters, multiple model adaptive estimation (MMAE) routines can be utilized for parameter and state estimates. MMAE algorithms involve constructing a bank of recursive estimators, each assuming a different hypothesis for the systems dynamics. This research has three distinct, but related, contributions to satellite attitude dynamics and estimation. In the first part of this research, MMAE routines employing parallel banks of unscented attitude …
Improving Real-World Performance Of Vision Aided Navigation In A Flight Environment, Donald T. Venable
Improving Real-World Performance Of Vision Aided Navigation In A Flight Environment, Donald T. Venable
Theses and Dissertations
The motivation of this research is to fuse information from an airborne imaging sensor with information extracted from satellite imagery in order to provide accurate position when GPS is unavailable for an extended duration. A corpus of existing geo-referenced satellite imagery is used to create a key point database. A novel algorithm for recovering coarse pose using by comparing key points extracted from the airborne imagery to the reference database is developed. This coarse position is used to bootstrap a local-area geo-registration algorithm, which provides GPS-level position estimates. This research derives optimizations for existing local-area methods for operation in flight …
Mechanical Properties And Fatigue Behavior Of Unitized Composite Airframe Structures At Elevated Temperature, Mohamed Noomen
Mechanical Properties And Fatigue Behavior Of Unitized Composite Airframe Structures At Elevated Temperature, Mohamed Noomen
Theses and Dissertations
The tension-tension fatigue behavior of a newly developed unitized composite material system was investigated. The unitized composite consisted of a polymer matrix composite (PMC) co-cured with a ceramic matrix composite (CMC). The PMC portion consisted of an NRPE high-temperature polyimide matrix reinforced with carbon fibers woven in an eight harness satin weave (8HSW). The CMC layer is a single-ply non-crimp 3D orthogonal weave composite consisting of ceramic matrix reinforced with glass fibers. In order to assess the performance and suitability of this composite for use in aerospace components designed to contain high-temperature environments, mechanical tests were performed under temperature conditions …
Orbit Determination Using Vinti's Solution, Steven P. Wright
Orbit Determination Using Vinti's Solution, Steven P. Wright
Theses and Dissertations
Orbital altitudes congested with spacecraft and debris combined with recent collisions have all but negated the Big Sky Theory. As the sheer number of orbital objects to track grows unbounded so does interest in prediction methods that are rapid and minimally computational. Claimed as the \other solvable solution, the recently completed solution too orbital motion about the earth, based on Vinti's method and including the major effects of the equatorial bulge, opens up the prospect of much more accurate analytical models for space situational awareness. A preliminary examination of this solution is presented. A numerical state transition matrix is found …
The Scaling Of Loss Pathways And Heat Transfer In Small Scale Internal Combustion Engines, Joseph K. Ausserer
The Scaling Of Loss Pathways And Heat Transfer In Small Scale Internal Combustion Engines, Joseph K. Ausserer
Theses and Dissertations
Prior literature indicates fuel conversion efficiency and normalized power deteriorate increasingly rapidly with decreasing displacement, but does not fully reveal the driving losses. The literature also suggested that increasing losses relax the required fuel anti-knock index (AKI), but offered conflicting conclusions on the performance impact. This comprehensive experimental study of three, 28 cm3 to 85 cm3 displacement, commercial-off-the-shelf (COTS), two-stroke ICEs identified short-circuiting as having the most deleterious impact on COTS engine performance in this size range. Heat transfer losses were comparable to larger engines for displaced volumes greater than 10 cm3. An engine friction model was developed that uses …
Optimal Control Of An Uninhabited Loyal Wingman, Clay J. Humphreys
Optimal Control Of An Uninhabited Loyal Wingman, Clay J. Humphreys
Theses and Dissertations
As researchers strive to achieve autonomy in systems, many believe the goal is not that machines should attain full autonomy, but rather to obtain the right level of autonomy for an appropriate man-machine interaction. A common phrase for this interaction is manned-unmanned teaming (MUM-T), a subset of which, for unmanned aerial vehicles, is the concept of the loyal wingman. This work demonstrates the use of optimal control and stochastic estimation techniques as an autonomous near real-time dynamic route planner for the DoD concept of the loyal wingman. First, the optimal control problem is formulated for a static threat environment and …
Cavity Geometric Features And Entrainment Characterization Resulting From A Ballistically Induced Hydrodynamic Ram Event, Andrew J. Lingenfelter
Cavity Geometric Features And Entrainment Characterization Resulting From A Ballistically Induced Hydrodynamic Ram Event, Andrew J. Lingenfelter
Theses and Dissertations
Hydrodynamic Ram can cause damage to industrial and aircraft systems. The resulting transient spray increases the probability of fire. To better understand the driving mechanisms behind transient spray, internal, and external measurements of the cavity geometry, and entrained flow field were accomplished. Research determined cavity contraction and separation are pre-cursors to the initiation of the transient spray phases. The entrained flow measurement required development of a new and novel technique using a continuous wave laser and atomized water particles. The peak mass flow correlated well with cavity geometric features, such as cavity contraction. Using the mass flow, cavity diameter at …
Test And Verification Of A Cubesat Attitude Determination And Control System In Variable Magnetic Fields, Eric A. Bassett
Test And Verification Of A Cubesat Attitude Determination And Control System In Variable Magnetic Fields, Eric A. Bassett
Theses and Dissertations
The Center for Space Research and Assurance (CSRA) at the Air Force Institute of Technology (AFIT) continues to explore CubeSat initiatives for solving many current space security issues. Regardless of the mission requirements, the success of the Cube- Sat on orbit frequently depends on the Attitude Determination and Control System (ADCS) functioning correctly. Previous research at AFIT has demonstrated single axis control on a spherical air bearing test bed incorporated within a Helmholtz cage utilizing artificially strong magnetic fields for better signal to noise ratios which are not experienced on orbit. This research explores the process of redesigning, testing, and …
Design, Manufacturing, And Testing Of A Small Through-Flow Wave For Use Within The Brayton Cycle, Micahel J. Mcclearn
Design, Manufacturing, And Testing Of A Small Through-Flow Wave For Use Within The Brayton Cycle, Micahel J. Mcclearn
Theses and Dissertations
With the ever growing popularity of drones and other unmanned aerial vehicles for military, commercial, and private usage, there is a desire to improve performance in terms of range, altitude, and flight speed. Current technology uses either electric motors or internal combustion engines: both piston and jet engine types. These sorts of engines undergo significant efficiency degradation as their size decreases. While some efficiency may be recovered via intensive design studies, the cycles are approaching the limit to their operating physics. A possible solution to this is to change the operating physics to something more immune to scaling losses; a …
Design And Experimentation Of A Premixed Rotating Detonation Engine, Ionio Q. Andrus
Design And Experimentation Of A Premixed Rotating Detonation Engine, Ionio Q. Andrus
Theses and Dissertations
Desire for a more efficient air breathing engine has shifted research attention to the Rotating Detonation Engine (RDE). Detonation is a more efficient combustion process than deflagration and provides a pressure gain. The RDE detonation cycle occurs in a compact volume to produce a high specific impulse engine. Computational fluid dynamic (CFD) models have predicted higher specific impulse and detonation wave speeds than has been seen in experimental RDE. The CFD models frequently assume premixed reactants and ignore inlet geometries to facilitate rapid computation. An experimental premixed RDE was sought to test if the premixed assumption in CFD was the …
Meeting The Dod’S Tactical Weather Needs Using Cubesats, Shayna K. Mckenney
Meeting The Dod’S Tactical Weather Needs Using Cubesats, Shayna K. Mckenney
Theses and Dissertations
This thesis investigates a CubeSat design that uses Commercial-Off-The-Shelf (COTS) components to capture, store, process, and downlink collected terrestrial weather data at resolutions near stat-of-the-art. The weather phenomena to be detected and transmitted in a timely manner are cloud formations, wind profiles, ocean currents, sea state, lightning, temperature profiles, and precipitation. It is hypothesized and shown that the proposed design will provide an improvement on the current U.S. tactical weather collection satellites because of the anticipated increased reliability and lowered cost to build and maintain the proposed CubeSat constellation. The methodology employed a multi-phase approach through the collective research of …
Investigation Of Thermal Scaling Effects For A Turbine Blade Leading Edge And Pressure Side Model, Ryan A. Lynch
Investigation Of Thermal Scaling Effects For A Turbine Blade Leading Edge And Pressure Side Model, Ryan A. Lynch
Theses and Dissertations
Recent experiments have attempted to quantify the overall cooling effectiveness at elevated temperature conditions. The Film Cooling Rig (FCR) at the Air Force Institute of Technology has been modified to better match the configuration of a similar large scale, low temperature rig at the Air Force Research Laboratory. This has enabled comparison and trend identification of how various properties scale from the low to high temperature condition. Various internal cooling and hole geometry configurations were investigated over a range of temperatures while utilizing the thermal scaling capability of Inconel 718. Film cooling trends and measures of overall effectiveness were matched, …
Visual-Ins Using A Human Operator And Converted Measurements, Turner J. Montgomery
Visual-Ins Using A Human Operator And Converted Measurements, Turner J. Montgomery
Theses and Dissertations
A method human operated INS aiding is explored in which the pilot identifies and tracks a ground feature of unknown position over a short measurement epoch using an E/O sensor. One then refers to Visual-INS. In contrast to current research trends, a human operator is entrusted with visually tracking the ground feature. In addition, a less conventional measurement linearization technique is applied to generate “converted” measurements. A linear regression algorithm is then applied to the converted measurements providing an estimate of the INS horizontal velocity error and accelerometer biases. At the completion of the measurement epoch, the INS is corrected …
Real-Time Implementation Of Vision-Aided Monocular Navigation For Small Fixed-Wing Unmanned Aerial Systems, Timothy I. Machin
Real-Time Implementation Of Vision-Aided Monocular Navigation For Small Fixed-Wing Unmanned Aerial Systems, Timothy I. Machin
Theses and Dissertations
The goal of this project was to develop and implement algorithms to demonstrate real-time positioning of a UAV using a monocular camera combined with previously collected orthorectified imagery. Unlike previous tests, this project did not utilize a full inertial navigation system (INS) for attitude, but instead had to rely on the attitude obtained by inexpensive commercial off-the-shelf (COTS) autopilots. The system consisted of primarily COTS components and open-source software, and was own over Camp Atterbury, IN for a sequence of flight tests in Fall 2015. The system obtained valid solutions over much of the flight path, identifying features in the …
Geolocation Of Rf Emitters Using A Low-Cost Uav-Based Approach, Michael A. Magers
Geolocation Of Rf Emitters Using A Low-Cost Uav-Based Approach, Michael A. Magers
Theses and Dissertations
The proliferation of unmanned aerial vehicles (UAVs) in both military and civilian settings has prompted great interest in finding new and innovative ways to utilize these tools. One such application is to locate ground-based radio emitters from a UAV platform. The goal of this research is to study the feasibility of a low-cost (on the order of $1000) UAV geolocation platform. To accomplish this goal, a series of both real-world flight testing and computer simulated scenarios were conducted. Simulations for different sensor uncertainties and approach path scenarios such as loiter and button hook patterns were investigated. Results showed that a …
Analysis Of A Near Real-Time Optimal Attitude Control For Satellite Simulators, Ryan M. Patrick
Analysis Of A Near Real-Time Optimal Attitude Control For Satellite Simulators, Ryan M. Patrick
Theses and Dissertations
Dynamic optimization of spacecraft attitude reorientation maneuvers can result in significant savings in attitude determination and control system size, mass, and power. Optimal control theory is generally applied using an open loop trajectory which is vulnerable to disturbances. A closed loop implementation of optimal control has been difficult to achieve due to the computational requirements needed to quickly compute solutions to the optimal control problem. This research focuses on evaluating a near real-time optimal control (RTOC) system for large angle slew maneuvers on the Air Force Institute of Technology's spacecraft simulator called SimSat. A near RTOC algorithm computes optimal control …
Electro-Mechanical Characterization Of Carbon Nanotube Sheets In Simulated Space Environments: The Dawn Of “Carbon Spacecraft”, Jacob W. Singleton
Electro-Mechanical Characterization Of Carbon Nanotube Sheets In Simulated Space Environments: The Dawn Of “Carbon Spacecraft”, Jacob W. Singleton
Theses and Dissertations
Carbon nanotube (CNT) materials are exciting candidates for spacecraft by virtue of their unprecedented specific mechanical and electrical properties. Analysis in this thesis identifies 14 types of CNT-sheets with distinct variables, and discovers the mechanisms controlling macroscopic properties. Specimen variables include acid treatment, polymer coatings, production method, and combinations. Mechanical testing includes tensile-tests and investigation with scanning electron microscopy and energy-dispersive x-ray spectroscopy. Physical properties testing include electromagnetic interference (EMI) shielding effectiveness (SE) and electrical conductivity. This research also highlights the resilience of CNT-sheets to atomic oxygen and thermal fatigue qualifying them for performance in space. EP CNT-sheets have decreased …
Toward Automated Aerial Refueling: Relative Navigation With Structure From Motion, Kevin W. Colson
Toward Automated Aerial Refueling: Relative Navigation With Structure From Motion, Kevin W. Colson
Theses and Dissertations
The USAF's use of UAS has expanded from reconnaissance to hunter/killer missions. As the UAS mission further expands into aerial combat, better performance and larger payloads will have a negative correlation with range and loiter times. Additionally, the Air Force Future Operating Concept calls for \formations of uninhabited refueling aircraft...[that] enable refueling operations partway inside threat areas." However, a lack of accurate relative positioning information prevents the ability to safely maintain close formation flight and contact between a tanker and a UAS. The inclusion of cutting edge vision systems on present refueling platforms may provide the information necessary to support …
Improved Performance By The Tie-Gcm With The Inclusion Of Helium As A Major Species, Fredrick R. Schmidt
Improved Performance By The Tie-Gcm With The Inclusion Of Helium As A Major Species, Fredrick R. Schmidt
Theses and Dissertations
When considering the neutral constituents in the upper thermosphere and exosphere, helium needs to be accounted for as a major species. As detailed by Emmert [2015], most first-principle models do not consider helium a major species when solving for diffusion and collisions within the atmosphere. First-principle, physics-based models hold a distinct advantage of seasonal variations and spatial resolution over empirical models which leads to a more realistic depiction of the atmosphere. The National Center for Atmospheric Research’s (NCAR) self-consistent, physics-based Thermosphere-Ionosphere-Electrodynamic General Circulation Model (TIE-GCM) has been updated to take into account this neutral constituent in its calculations. The major …
Evaluation Of Verification Approaches Applied To A Nonlinear Control System, Kerianne H. Gross
Evaluation Of Verification Approaches Applied To A Nonlinear Control System, Kerianne H. Gross
Theses and Dissertations
As the demand for increasingly complex and autonomous systems grows, designers may consider computational and artificial intelligence methods for more advanced, re- active control. While the performance gained by such increasingly intelligent systems may be superior to traditional control techniques, the lack of transparency in the systems and opportunity for emergent behavior limits their application in the field. New verification and validation methods must be developed to ensure the output of such controllers do not put the system or any people interacting with it in danger. This challenge was highlighted by the former Air Force Chief Scientist in his 2010 …
Multi-Cubesat Deployment Strategies: How Different Satellite Deployment Schemes Affect Satellite Separation And Detection For Various Types Of Constellations And Missions, Scott A. Biehl Jr.
Multi-Cubesat Deployment Strategies: How Different Satellite Deployment Schemes Affect Satellite Separation And Detection For Various Types Of Constellations And Missions, Scott A. Biehl Jr.
Theses and Dissertations
As economics drive an increased demand for small satellites and, consequently, an increase in the number of satellites deployed per launch, different deployment schemes and their effects on satellite dynamics must be well understood. While there are advantages to deploying multiple satellites at once, users may have trouble with tracking, identifying, and communicating with their satellites. This investigation examines the deployment of eight 3U CubeSats, and the resulting relative motion within a constellation. Both the distance between any two satellites within a constellation and the volume of a polygon encompassing a constellation are used to analyze the satellite dynamics within …
Liquid Fuel Film Cooling: A Cfd Analysis With Hydrocarbon Fuel, Jacob D. Bills
Liquid Fuel Film Cooling: A Cfd Analysis With Hydrocarbon Fuel, Jacob D. Bills
Theses and Dissertations
Cooling of liquid rocket engine combustion chambers and nozzles is a critical component to liquid rocket engine design. A common method of cooling is liquid fuel film cooling. Liquid fuel is injected along the surface of the wall to act as a barrier against the core combustion gases. A numerical model is developed for simulating liquid fuel _lm cooling in a rocket engine using a hydrocarbon fuel. The model incorporates turbulent multiphase ow with species transport within the commercial ANSYS® Fluent CFD software. Conjugate heat transfer is simulated through walls containing embedded cooling channels. A novel User Defined Function is …
Formation Flight Of Earth Satellites On Low-Eccentricity Kam Tori, Christopher T. Craft
Formation Flight Of Earth Satellites On Low-Eccentricity Kam Tori, Christopher T. Craft
Theses and Dissertations
The problem of Earth satellite constellation and formation flight is investigated in the context of Kolmogorov-Arnold-Moser (KAM) theory. KAM tori are constructed utilizing Wiesel’s Low-Eccentricity Earth Satellite Theory, allowing numerical representation of the perturbed tori describing Earth orbits acted upon by geopotential perturbations as sets of Fourier series. A maneuvering strategy using the local linearization of the KAM tangent space is developed and applied, demonstrating the ability to maneuver onto and within desired torus surfaces. Constellation and formation design and maintenance on KAM tori are discussed, along with stability and maneuver error concerns. It is shown that placement of satellites …
Localized Plasma Measurement During Instability Modes In A Hall Thruster, David A. Cunningham
Localized Plasma Measurement During Instability Modes In A Hall Thruster, David A. Cunningham
Theses and Dissertations
Hall thrusters are a key technology for current and future unmanned satellites, striking a balance between thrust and fuel economy suitable for many mission profiles of interest. Despite their extensive flight heritage and a large body of research, many phenomena occurring in the plasma discharge of Hall thrusters are not well understood. A combination of intrusive and non-intrusive measurement techniques were used to investigate the properties of the exhaust plume of two Hall thrusters and correlate optical characteristics of oscillating modes with the plasma potential and azimuthal current distribution during those modes. A strong trend was found associating the optical …
Conceptual Design, Structural Analysis, And Design Space Exploration Of A Vacuum Lighter Than Air Vehicle, Brian C. Cranston
Conceptual Design, Structural Analysis, And Design Space Exploration Of A Vacuum Lighter Than Air Vehicle, Brian C. Cranston
Theses and Dissertations
The research detailed in this study investigates an internal vacuum as well as its optimal structural design, utilizing currently available materials, as an alternative to traditional gases to create and sustain buoyancy in lighter than air vehicles. To date, the consideration of a vacuum lighter than air vehicle has been limited to three sources of literature, the earliest of which dates back to 1663. This study will initially summarize and review this literature. We will then combine finite element analysis, dimensional analysis, design of experiments, and response surface methodology studies to explore the feasibility, and the functional design of a …
Key Detection Rate Modeling And Analysis For Satellite-Based Quantum Key Distribution, Jonathan C. Denton
Key Detection Rate Modeling And Analysis For Satellite-Based Quantum Key Distribution, Jonathan C. Denton
Theses and Dissertations
A satellite QKD model was developed and validated, that allows a user to determine the optimum wavelength for use in a satellite-based QKD link considering the location of ground sites, selected orbit and hardware performance. This thesis explains how the model was developed, validated and presents results from a simulated year-long study of satellite-based quantum key distribution. It was found that diffractive losses and atmospheric losses define a fundamental trade space that drives both orbit and wavelength selection. The optimal orbit is one which generates the highest detection rates while providing equal pass elevation angles and durations to multiple ground …
Orbital Resonances In The Vinti Solution, Laura M. Duffy
Orbital Resonances In The Vinti Solution, Laura M. Duffy
Theses and Dissertations
The Vinti Solution offers a more accurate model than the two-body problem as an orbital propagator. Unfortunately, the Vinti solution contains small divisors near orbital resonances in the perturbative terms of the Hamiltonian, which lead to inaccurate orbital predictions. One approach to avoid the small divisors is to apply transformation theory. The methodology of this research is to identify the perturbative terms of the Vinti Solution, perform a coordinate transformation, and derive the new equations of motion for the Vinti system near orbital resonances. The analysis in this research focuses on the 2:1 resonance, which includes the Global Positioning System. …
Spectroscopic Measurement Of Gas Temperature In Small Internal Combustion Engines, Matthew J. Deutsch
Spectroscopic Measurement Of Gas Temperature In Small Internal Combustion Engines, Matthew J. Deutsch
Theses and Dissertations
The Small Engine Research Bench (SERB) was used previously to measure spatially and temporally averaged heat flux, as well as local, instantaneous heat flux at several external locations, for a series of small engines (1 - 10 kW). This investigation obtained time averaged crank angle resolved measurements of the in-cylinder gas temperature using Fourier transform infrared (FTIR) absorption thermometry. The results, coupled with heat flux measurements, will enable the validation or refinement of existing thermal energy loss models.