Master of Science in Aerospace Engineering

Series

Master of Science in Aerospace Engineering

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https://hdl.handle.net/1853/73271

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Degree Series

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Organizational Unit

Daniel Guggenheim School of Aerospace Engineering

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Now showing 1 - 10 of 295

Conceptual Effectiveness-Based Hypersonic Evaluation (CEBREN)

(Georgia Institute of Technology, 2022-05-03) Van Der Linden, James C. A.

For decades, the United States has largely been uncontested in its quest to advance its national interests in every domain – to protect the American people, promote prosperity, preserve peace, and advance American influence. To maintain technological superiority, the National Security Strategy calls upon the military to field new capabilities that clearly overmatch US adversaries in lethality. Furthermore, the US military has identified hypersonics as an area of interest to stay competitive on the global stage. Hypersonics have been around for over 70 years ranging from the X-20 to the Space Shuttle; however, these projects were products of the traditional design-build-test methodology which often never saw flight. This design-build-test methodology is unable to meet the demands of technological growth and complexity and often drives up costs and overruns. Thus, there is a need to develop a new methodology for assessing hypersonic weapon capability rapidly to support interactive decision making for conceptual development. Hypersonic conceptual design distinguishes itself from traditional aircraft design because the disciplines that must be considered are highly coupled and tightly integrated which drastically increases design risk due to sources of uncertainty. Additionally, it is difficult for engineers to evaluate revolutionary designs because the historical data necessary to perform initial analysis likely is unavailable. Due to this uncertainty, conceptual design is critical because the decisions made have profound ramifications throughout the entire process. To address this uncertainty, physical experiments are required to provide the highest quality of data; however, they are extremely limited in scope and expensive. Hence, there is a need to make well informed decisions at the conceptual design level when designing novel hypersonic vehicles. Due to the coupling of disciplines within hypersonic conceptual design, a Multidisciplinary Design Analysis and Optimization (MDAO) environment was used to design novel hypersonic vehicles. To aid in evaluating these alternatives, agent-based modelling was used to study the effectiveness of the vehicles through operational analysis (OA). By integrating an MDAO environment with an OA framework, novel hypersonic vehicles were constructed, and their capabilities assessed through a process known as effectiveness-based design (EDB). Within EBD, the design objective is shifted from performance metrics (e.g., weight, range, etc.) to effectiveness metrics (e.g. targets killed, survival, etc.) which allows decision makers to consider and understand the implications of design-space-limiting decisions earlier in the process. This shifts away from over-defining requirements before exploring potential best solutions to the problem. Thus, the purpose of this thesis presents a new methodology to address the need of designing and rapidly assessing hypersonic capability to better inform the decision maker through the integration of OA within an MDAO environment thereby closing the loop by coupling the effectiveness to vehicle design parameters.
Investigating Lean Blowout of an Alternative Jet Fuel in a Gas Turbine Combustor

(Georgia Institute of Technology, 2022-01-05) Narayanan, Vijay

In the global effort to reduce the climate impact of combustion emissions, sustainable aviation fuels offer the ease and reliability of conventional petroleum-derived jet fuels without the significant pollutant effects. Ongoing research efforts include experimental testing of alternative jet fuels to identify fuel candidates that produce less pollutant combustion products and are cheaper and environmentally cleaner to source than conventional jet fuels. Fuel lean combustion already reduces the emissions of jet engines and increases fuel efficiency, but lean blowout (LBO) can occur at reduced throttle and minimum power scenarios such as descent. Lean blowout (LBO) has been identified as a critical figure of merit to ensure the stability of alternative jet fuels in the place of conventional fuels. This work aimed to further understand the LBO phenomenon, leveraging computational studies of the alternative fuel designated C-5 by the National Jet Fuel Combustion Program (NJFCP). The fuel sensitivity of LBO has been established by the NJFCP’s participants recently. In this thesis, the chemical kinetics for C-5 is first verified using zerodimensional (0-D) and one-dimensional (1-D) studies and then this is followed by three dimensional (3D) large-eddy simulations (LES). In LES to observe LBO, a direct-step and gradual equivalence ratio reduction were separately employed to assess fuel sensitivity of LBO against available experimental data. The time histories of pressure, temperature, and composition were analyzed for precursor signatures of LBO both inside and outside the flame. Localized extinction, a reduction in the vortex breakdown bubble size and magnitude, and a reduction in the exhaust velocity were all observed to occur during the LBO event.
A Methodology to Capture the Acoustic Properties of Small Unmanned Aerial System Noise Using a Novel Frequency Weighting

(Georgia Institute of Technology, 2021-08-03) Gabrielian, Ana Bella

As the advent of Urban Air Mobility (UAM) draws near, the obstacles to such vehicles and operations grow larger. One of these obstacles is the noise created through the operation of these air vehicles. Noise is a public concern as excessive exposure has been shown to contribute to lack of sleep, lack of cognitive abilities in children, and decline in overall cardiac health. There is extensive noise policy for traditional aircraft; however, no noise policy exists for vehicles in the category of UAM. In this thesis, the understanding of small Unmanned Aerial System (sUAS) noise is detailed by investigating the competence of current metrics to describe the annoyance that is created by such vehicles. With regulatory entities such as the Federal Aviation Administration (FAA) forecasting the viability of last mile delivery by sUASs by 2030, it is imperative that acoustical understanding is developed in parallel with this emerging technology. As a part of a NASA research effort, the Design Environment for Novel Vertical Lift Vehicles (DELIVER), a psychoacoustic test on sUASs was conducted to measure human annoyance toward these vehicles in comparison to current delivery vehicles. The study had two main findings: at the same decibel level, test subjects found sUASs more annoying than they did delivery vehicles and the correlation between annoyance and decibel level using four different noise metrics was relatively low. In a preliminary comparison of spectral content between a helicopter and one of the sUASs in this study, it is shown that the sUAS’s spectral content has more tones in the region of frequencies in which humans are especially sensitive. To account for human sensitivity to these tones, the hypothesis is posed: A new frequency weighting, which allows Sound Exposure Level to better correlate with human annoyance caused by an sUAS noise event, will create a larger SEL contour area that is more indicative of sUAS noise. In the first phase of the approach, this hypothesis was tested by creating a design of experiments of different frequency weightings to find a new weighting with a higher correlation coefficient. The resulting frequency weighting (the X-weighting) increased the R2 value from 0.784 to 0.853. In the second phase, Sound Exposure Level contours were created using the new frequency weighting and current frequency weightings in ANOPP2. The SEL 65 dB contour experienced a 79%, 18%, and 78% increase in width, length and area respectively between then X- and the A-weighting for one of the sUASs investigated. This methodology grants stakeholders such as regulators and original equipment manufacturers a process to assess frequency weightings and their efficacy in capturing human annoyance; in doing so, this could enable all sUAS stakeholders to create a common “language” with which to discuss the noise created by these vehicles effectively.
A METHODOLOGY FOR CONDUCTING DESIGN TRADES FOR A SMALL SATELLITE LAUNCH VEHICLE WITH HYBRID ROCKET PROPULSION

(Georgia Institute of Technology, 2021-07-28) Caglar, Havva Irem

The commercial space industry has recently seen a paradigm shift related to the launch of a small satellite into Low Earth Orbit. In the past, a small satellite was launched as a secondary payload with a medium or heavy launch vehicle where the primary payload placed a constraint on the orbit and schedule. Today, a dedicated launch of a small launch vehicle is the main operational concept to launch a small payload. Many Smallsat Launch Vehicles (SLV) have been under development by the commercial space industry to improve these launch services in recent years. Despite these efforts, the specific prices per launch are still high, and reducing these prices further remains a challenge. One promising technology candidate to reduce costs for SLV is hybrid rocket propulsion which has matured recently with some cost and safety advantages. Although hybrid rocket propulsion faces a number of challenges, including a low regression rate and combustion instabilities, academia and commercial companies have invested significant resources in developing this technology. With this motivation, this thesis has focused on the conceptual design of SLV with hybrid rocket propulsion. Moreover, a cost reduction strategy currently used by the commercial space industry was observed to be the development of a unique engine and using multiple of them in a launch vehicle. Following this trend, the vehicle concept investigated in this thesis was an expendable ground-launched vehicle with some architectural variables such as the number of stages and the number of hybrid motors in each stage. The design trade-off studies of such a small multistage launch vehicle with multiple hybrid motors in each stage require very long times especially when traditional point design approaches are used. As the number of design variables increase, the design space exploration becomes even more challenging. To provide a solution to this problem, a methodology for rapid conceptual design of such a vehicle was presented in this thesis. A physics-based conceptual design approach was followed in this study since SLV are relatively new concepts without much historical performance data. To conduct a multidisciplinary analysis, a physics-based, integrated modeling and simulation environment was constructed with four core disciplines: trajectory analysis, aerodynamics, propulsion, and weight. Aerodynamics and propulsion analysis were conducted using a first-principles approach, which was based on fundamental theories. A 3 Degree of Freedom (DOF) industrial, transparent, physics-based trajectory analysis software was used in this study based on availability. However, any other trajectory analysis software that a system designer is familiar with can be used in its place. In other words, the methodology developed in this thesis would remain unchanged if another trajectory analysis software were used. The weight discipline was represented at a high level by using Propellant Mass Fraction (PMF) design variable. A multidisciplinary modeling and simulation environment for launch vehicles may be computationally expensive depending on the fidelity levels of each discipline. Moreover, trajectory optimization is included in a launch vehicle design process conventionally which may be also computationally expensive depending on the optimization method. This expense poses a difficulty in performing a trade-off study for hundreds of vehicle design alternatives within the constraints of the schedule in the conceptual design phase. Because of this, trajectory optimization was removed from the design process to speed up the process by selecting a constant controller design. The methodology developed in this thesis consisted of two sequential steps. In the first step, a surrogate modeling approach was followed to replace the Modeling and Simulation (M&S) environment. A DOE method and a surrogate modeling method suitable to this problem were searched in this part. To cover the design space, a hybrid DOE consisting of a Fast Flexible Filling DOE and a three-level Full Factorial DOE was chosen. Artificial Neural Networks method was selected to fit approximation models because of the type of design variables (both continuous and discrete variables) and nonlinearity of the problem. The first experiment was conducted to test this hypothesis. As a result, it was demonstrated that this approach can provide accurate surrogate models for any desired response. In the second step, the specific mechanical energy-based design trade-off method was developed using some statistical methods. This method estimates the lower bound of the vehicles’ actual specific mechanical energy where the vehicles can be rapidly designed by using surrogate models. This lower bound was predicted with the help of the prediction interval of the specific mechanical energy’s model fit error. To fit the surrogate models, the necessary data were gathered by running the DOE in the integrated M&S environment while imposing some terminal conditions on the altitude of the vehicles analyzed in this environment. Specifically, the surrogate models of specific mechanical energy and flight path angle were used to design the vehicles rapidly. The second experiment was conducted to test this hypothesis. As a result, the actual specific mechanical energies computed via trajectory optimization were found to be consistent with the predictions. Overall, it was demonstrated that the proposed method enables a system designer to rapidly design some feasible vehicles, which can then proceed to the next design phase for further comparison, analysis, and design.
A Methodology for Demand Assessment and Integrated Schedule Design and Fleet Assignment Applied to Thin-Haul Scheduled Operations

(Georgia Institute of Technology, 2021-07-07) Da Silva Oliveira, Thayna

The thin-haul market is characterized by short-range routes with low demand, occasionally served by commuter airlines. Historically, commuter operators have not been able to maintain profitable operations in this market, migrating to longer and more profitable routes throughout the years. As a result, many small cities have lost their air service and airports have become underutilized. Aiming to change this scenario, many studies have focused on the development of vehicle technologies to promote thin-haul scheduled operations and the assessment of potential demand. This thesis investigates thin-haul operations from the airline's point of view, aiming to understand how flight operations optimization can aid commuter operators to improve profitability and, ultimately, to restore the air service to small communities. Despite the low individual demand of each thin-haul route, an opportunity for profitability may exist if the origin-destination pairs are effectively served. This can be achieved if the airline makes the right schedule decisions, i.e., strategically defines when and where to fly, as well as the assignment of the aircraft with the right capacity to the right flight leg. These problems are part of the schedule planning process and are known in the literature as schedule design and fleet assignment (SD&FA). However, the lack of historical data and baseline schedule for thin-haul operations imposes challenges for demand estimation and SD&FA applications. Therefore, the contribution of this thesis is in the development of a methodology for demand assessment and integrated SD&FA applied to thin-haul operations that can overcome the aforementioned challenges. This is achieved by investigating thin-haul demand based on the competition with alternative modes of transport and by coupling the current SD&FA techniques with the concept of hourly demand distribution. The proposed methodology is implemented in a framework that allows different operational scenarios to be evaluated based on the operations metrics of effectiveness, which includes the airline profit, the potential thin-haul demand served, and the passenger time savings. Such framework enables stakeholders to understand the key elements that lead to profitable thin-haul operations, the extent to which the air service can be expanded, and the potential benefits for passengers and cities. The experiments conducted in this thesis demonstrated that the methodology can successfully perform SD&FA applied to thin-haul operations and determine the true market share, i.e., the potential demand that can be profitably served by an air carrier. Additional case studies highlighted that more efficient operations can be achieved if airlines adopt a mix of point-to-point and connecting flights, and that hub location and aircraft attributes can significantly impact the effectiveness of the operations.
USING A HANDS-ON ROBOTICS PROJECT TO AFFECT SKILL DEVELOPMENT IN A CONTROL ANALYSIS COURSE

(Georgia Institute of Technology, 2021-05-05) Inghilleri, Niccolo

This study aims to assess the impact on skill development of a hands-on experimentation and learning device within the undergraduate aerospace control analysis curriculum at Georgia Institute of Technology. The Transportable Rotorcraft Electronics Control System (TRECS) take-home lab kit was used as a hands-on learning treatment on 37.5% (n=24) of the Fall 2020 Control Analysis course taught by Chance McColl. The other students (n=40) in the course were taken as a control group. A Likert scale skill evaluation survey was performed to determine which skills are developed while using the TRECS. The response distributions and an accompanying Mann Whitney U-test can be found in the results section. On the topic of optimal control algorithms, which are extensively covered in the course lecture material and applied in the TRECS project, Users and Nonusers reported significantly (p=0.10) increased response and Users were found to have significantly (p=0.10) improved beyond Nonusers. Response distributions for topics including PID control, embedded software, and other electronics were not found to change significantly throughout the course, despite the application of the TRECS treatment or the presence of the topic in the course curriculum. The other goal of this research was to propose an improved study which addresses the limitations to this dataset such as small sample sizes, self-reports, sole focus on development of course-specific subject matter and selection bias from the lack of random assignment of the treatment. The recommendations for a future study are aimed to improve trustworthiness, increase transferability, and incorporate multiple verification elements including the development of a new skill assessment that could evaluate students’ application-level understanding of course concepts.
Additive Manufacturing of Compliant Mechanisms for Deployable Aerospace Structures

(Georgia Institute of Technology, 2021-04-27) Gebara, Christine

In the past 10 years, complex deployable structures have become common on JPL CubeSats (e.g. RainCube, MARCO, ISARA) and large-scale spacecraft (e.g. SMAP, SWOT, NISAR, Starshade). As new, ambitious missions are pursued, there is an increased need for more mass and volume efficient deployments (higher packing density). Over the same timeframe, additive manufacturing (AM) has enabled the fabrication of new forms of flight hardware including the PIXL instrument structure, the Moxie instrument, and the RainCube antenna structure. However, AM of compliant mechanisms has not been leveraged to design deployable space structures. AM of compliant mechanisms within deployable structures (e.g. antennas, solar panels, booms), could drastically lower part counts, create novel structural tuning methods, and design previously impossible geometries. Utilizing AM would therefore lead to deployable spacecraft elements with higher mass and volume efficiencies. AM of compliant mechanisms (4D printing) is an active research area. The ability to print these mechanisms in polymers has been demonstrated. However, metal 4D-printing is still a maturing technology for aerospace applications. One area of interest is additive manufacturing of flexure hinges for flat reflectarray antennas, radiators, and solar panels. Another application is the ability to print structurally embedded spring elements that are geometrically tuned for a specific deployable structure. This could result in numerous benefits. Primarily, embedding compliant mechanisms directly where they are used would simplify deployment dynamics, thus also simplifying the characterization and control of the deployment. Second, printing structurally embedded compliant elements could enable systems that are otherwise impossible to assemble or manufacture. For example, the ability to print a structurally embedded torsional spring within the hinge mechanisms for a SWOT-type deployable mast could ease manufacturing problems, decrease part count, decrease mechanism shimming, and improve reliability.
LES of Turbulent Premixed Flame Kernel Formation and Development

(Georgia Institute of Technology, 2020-12-17) Lambert, Alexander

Spark ignition of flammable mixtures is highly sensitive to early and local conditions. Kernel formation and subsequent flame development are largely governed by turbulent conditions and interactions with igniter geometry. In order to investigate this phenomenon, the use of Large Eddy Simulation (LES) is examined for (1) modelling spherical turbulent flame development, and (2) simulating spark ignition in a channel with either laminar or turbulent inflow. A comparison between LES spherical flame simulation is made to FSD-LES results as well as experimental measurements from previous studies. For spark ignition experiments, we characterize the temporal evolution of the ignition process, and demonstrate the dependence on early velocity fluctuations and local conditions.
An acoustical based approach to conceptual design of non-traditional rotorcraft configurations

(Georgia Institute of Technology, 2020-07-31) Huelsman, Sara

As interstate and highway traffic increases, commute times become drastically large. Such large commute times create fatigue and take away from productive hours at work, or joyful hours at home. The idea of urban air mobility becomes increasingly more attractive and viable as technology improves. These more advanced rotor concepts have opened up the design space in order to satisfy a very different mission profile. Nontraditional rotor concepts can provide performance benefits within a new use of the design. Noise becomes an increasing concern since the mission profile allows these vehicles flying much closer to communities. This research investigates three configurations of rotorcraft: coaxial rotors, ducted rotors, and ducted coaxial rotors, to provide insight on how design configuration changes the acoustics of these vehicles. The methodology developed is a parametric environment to provide detail on influential parameters for a model to be created for use within the conceptual design stage. This provides designers a process for capturing acoustic changes early on in the design process, while these new vehicles are still being developed.
Hypersonic shape parameterization using class – shape transformation with stagnation point heat flux

(Georgia Institute of Technology, 2019-05-01) Fan, Justin

In recent years, hypersonics is undergoing a major resurgence that is primarily driven by domestic and foreign militaries to have an advanced and unchallenged weapon system. China and Russia have tested hypersonic systems, and the United States is pushing to match and exceed adversarial capabilities. While the concept of hypersonic vehicles is not a recently conceived concept, it has experienced turbulent progress throughout the decades. Hypersonic vehicles are inherently complex vehicles to design due to intricate couplings between design disciplines: aerodynamics, aerodynamic heating, trajectory, structures, and controls. As computational analysis tools in these disciplines have progressed, the geometries and vehicles must progress as well. For aerodynamic purposes, hypersonic vehicles often contain sharp leading-edges to achieve high lift-to-drag properties. However, the use of sharp leading edges at hypersonic velocities also results in severe aerodynamic heating. The severe aerodynamic heating can lead to the destruction of materials and the entire vehicle, as was the case in the Space Shuttle Challenger accident. The aerodynamic heating, specifically the stagnation point heat flux, has been found to be directly related to the leading-edge radius of a given shape. The purpose of this thesis is to implement the shape parameterization method known as the class-shape transformation (CST) method with stagnation point heat flux. The CST method is a proven method in research where geometries can be optimized in aerodynamics to obtain maximum lift-to-drag ratio (L/D). Instead of taking a shape and having to perform time-consuming analyses to determine the leading-edge heat flux, an initial geometry can be determined with approximate hypersonic operating conditions. The objective of this research is to 1) leverage a parametric shaping modeling method to generate geometries that 2) incorporates an aspect of hypersonic aerodynamic heating effects on the geometry and 3) optimize the new geometry for maximum aerodynamic efficiency.