abstract: This thesis describes a longitudinal dynamic analysis of a large, twin-fuselage aircraft that is connected solely by the main wing with two tails unattached by a horizontal stabilizer. The goal of the analysis is to predict the aircraft’s behavior in various flight conditions. Starting with simple force diagrams of the longitudinal directions, six equations of motion are derived: three equations defining the left fuselage’s motion and three equations defining the right fuselage’s motion. The derivation uses a state-vector approach. Linearization of the system utilizes a Taylor series expansion about different trim points to analyze the aircraft for small disturbances about the equilibrium. The state transition matrix shows that there is a coupling effect from the reactionary moments caused by the two empennages through the connection of the main wing. By analyzing the system in multiple flight conditions: take-off, climb, cruise, and post-separation of payload, a general flight envelope can be developed which will give insight as to how the aircraft will behave and the overall controllability of the aircraft. The four flight conditions are tested with published Boeing 747 data confirmed from multiple sources. All four flight conditions contain unstable phugoid modes that imply instability increases with decreasing torsional spring stiffness of the wing or as the structural damping drops below 4%. / Dissertation/Thesis / Masters Thesis Aerospace Engineering 2017

abstract: Materials with unprecedented properties are necessary to make dramatic changes in current and future aerospace platforms. Hybrid materials and composites are increasingly being used in aircraft and spacecraft frames; however, future platforms will require an optimal design of novel materials that enable operation in a variety of environments and produce known/predicted damage mechanisms. Nanocomposites and nanoengineered composites with CNTs have the potential to make significant improvements in strength, stiffness, fracture toughness, flame retardancy and resistance to corrosion. Therefore, these materials have generated tremendous scientific and technical interest over the past decade and various architectures are being explored for applications to light-weight airframe structures. However, the success of such materials with significantly improved performance metrics requires careful control of the parameters during synthesis and processing. Their implementation is also limited due to the lack of complete understanding of the effects the nanoparticles impart to the bulk properties of composites. It is common for computational methods to be applied to explain phenomena measured or observed experimentally. Frequently, a given phenomenon or material property is only considered to be fully understood when the associated physics has been identified through accompanying calculations or simulations. The computationally and experimentally integrated research presented in this dissertation provides improved understanding of the mechanical behavior and response including damage and failure in CNT nanocomposites, enhancing confidence in their applications. The computations at the atomistic level helps to understand the underlying mechanochemistry and allow a systematic investigation of the complex CNT architectures and the material performance across a wide range of parameters. Simulation of the bond breakage phenomena and development of the interface to continuum scale damage captures the effects of applied loading and damage precursor and provides insight into the safety of nanoengineered composites under service loads. The validated modeling methodology is expected to be a step in the direction of computationally-assisted design and certification of novel materials, thus liberating the pace of their implementation in future applications. / Dissertation/Thesis / Doctoral Dissertation Aerospace Engineering 2018

abstract: This thesis uses an aircraft aerodynamic model and propulsion data, which represents a configuration similar to the Airbus A320, to perform trade studies to understand the weight and configuration effects of “out-of-trim” flight during takeoff, cruise, initial approach, and balked landing. It is found that flying an aircraft slightly above the angle of attack or pitch angle required for a trimmed, stabilized flight will cause the aircraft to lose speed rapidly. This effect is most noticeable for lighter aircraft and when one engine is rendered inoperative. In the event of an engine failure, if the pilot does not pitch the nose of the aircraft down quickly, speed losses are significant and potentially lead to stalling the aircraft. Even when the risk of stalling the aircraft is small, the implications on aircraft climb performance, obstacle clearance, and acceleration distances can still become problematic if the aircraft is not flown properly. When the aircraft is slightly above the trimmed angle of attack, the response is shown to closely follow the classical phugoid response where the aircraft will trade speed and altitude in an oscillatory manner. However, when the pitch angle is slightly above the trimmed condition, the aircraft does not show this phugoid pattern but instead just loses speed until it reaches a new stabilized trajectory, never having speed and altitude oscillate. In this event, the way a pilot should respond to both events is different and may cause confusion in the cockpit. / Dissertation/Thesis / Masters Thesis Aerospace Engineering 2018

abstract: The focus of this study is on evaluating the perceived service quality of a passenger using Self Service Technologies (SST) based service delivery systems at airports. Previously, studies have been conducted to evaluate the benefits of these service delivery systems for the service providers and in theory, the benefits the passengers or customers may receive from using these SSTs. However, not much research has been done comparing the benefits passengers perceive from the SSTs and how the same compares with the benefits perceived by passengers while using a conventional service-employee based service delivery system, for example, manned check-in desks at airports. The data for the study was collected by surveying passengers using the scale questionnaire designed by Lin and Hsieh in 2011, named SSTQUAL (Self Service Technologies Quality), to evaluate service quality delivered by SST based service delivery systems in terms of perceived functionality, enjoyment, design-assurance-convenience, security/privacy and customization. These different dimensions were compared among passengers who utilized Self Service Kiosks (SSKs) and passengers who used check-in-desks to check their luggage in. The data derived from the responses was analyzed using Multivariate Analysis of Variance (MANOVA) to compare the between-subject effects of the dimensions as well as the overall multivariate significance in the difference between the service quality perceived between the two check-in methods. It was found that though the cumulative perceived service quality was not influenced by the method of check-in, individual service quality dimensions like Enjoyment, Design, Convenience and Assurance were influenced by the check-in method. Positive correlation was also established between the method of check-in and customer behavioral intentions of recommending and using the respective airline’s service again as well as going through the process of using the respective airline’s SST again. Keywords: Self-Service Technologies, SSTQUAL, service-quality parameters, self check-in kiosks, manned check-in desks, technological readiness, customer behavioral intentions, MANOVA. / Dissertation/Thesis / Masters Thesis Technology 2018

<p> In recent times, there has been a shift in focus from component level to system level analysis and an increasing effort to understand and design resilience into the system. Several efforts have been carried out in creating metrics to analyse resilience. Understanding and implementing system resilience in complex System of Systems will help us in building safer and resilient systems.</p><p> System Importance Measures (SIMs) was formulated to analyse System of System resilience and help in designing a resilient SoS. Here, we operationalize these System Importance Measures for designing a resilient SoS. We first look at the existing methodology to improve the visual representation of system resilience and its usability. We demonstrate this using our first case study with a Naval warfare SoS.</p><p> We incorporate probability into the SIM formulation. We expand the existing SIMs to quantify the effects of disruptions and mitigation likelihoods. We built a second case study based on Air transportation networks and demonstrated our expanded metrics in both the case studies.</p><p> SIM based analysis of SoS resilience provides us with two different analysis of resilience, with and without probability. Having an outlook on how the resilience changes with a probability of disruptions can aid the designer making informed choices on design changes and help in creating a resilient SoS.</p><p>

<p> The altitude range between 120 and 300 km is relatively unexplored with regard to space weather, atmospheric models, climate observations, the global electric circuit, remote sensing, and intelligence gathering. This altitude range is not conducive to to in situ measurements due to the high magnitudes of drag that are experienced by satellites at these altitudes. The concept of air-breathing propulsion systems have been proposed to counteract drag. These propulsion systems produce thrust through electrostatic propulsion by ionizing the background neutral atmospheric particles. The atmospheric neutral particles that are the cause of drag at these altitudes are used as the fuel source for these air-breathing thrusters. Systems have been conceptually designed for larger satellites, but in this work we show that is possible for CubeSats to employ similar systems. CubeSats are a relatively new technology that have allowed low cost satellites to be built by a variety of entities including universities and private companies at low cost and with rapid development cycles. Due to current restrictions, CubeSats are not allowed to carry propellant. This limits CubeSats from maneuvering, formation flying, orbit raising, drag make-up, and deorbiting. However, this has not prevented the study and design of propulsion systems for CubeSats, with the anticipation of the propellant restrictions being lifted. </p><p> In this research, a concept for an air-breathing ion thruster is designed for the use in 3U, 6U, 12U, and 27U Cubesats. The design is created to be modular to this system, and each component is discussed separately. An analysis is conducted to determine the best inlet shape for capturing atmospheric particles. This analysis is conducted using a 3D Monte Carlo simulator. The ionization of atmospheric particles is investigated, and issues with ionization of the particles given the design of the system are discussed. Based on the expected inlet capture efficiency and ionization efficiency, the thrust capabilities of the system are projected for the various CubeSat standard sizes in LEO altitudes (80 km to 600 km). Analysis of the thrust based on CubeSat size, voltage, solar activity, and ionization efficiency is also conducted herein. This work shows that it is possible to build air-breathing propulsion systems for CubeSats with thrust exceeding the local drag in LEO altitudes.</p><p>

<p> Currently, railgun force modeling either uses the simple &ldquo;railgun force equation&rdquo; or finite element methods. It is proposed here that a middle ground exists that does not require the solution of partial differential equations, is more readily implemented than finite element methods, and is more accurate than the traditional force equation. To develop this method, it is necessary to examine the core railgun factors: power supply mechanisms, the distribution of current in the rails and in the projectile which slides between them (called the armature), the magnetic field created by the current flowing through these rails, the inductance gradient (a key factor in simplifying railgun analysis, referred to as L'), the resultant Lorentz force, and the heating which accompanies this action. Common power supply technologies are investigated, and the shape of their current pulses are modeled. The main causes of current concentration are described, and a rudimentary method for computing current distribution in solid rails and a rectangular armature is shown to have promising accuracy with respect to outside finite element results. The magnetic field is modeled with two methods using the Biot-Savart law, and generally good agreement is obtained with respect to finite element methods (5.8% error on average). To get this agreement, a factor of 2 is added to the original formulation after seeing a reliable offset with FEM results. Three inductance gradient calculations are assessed, and though all agree with FEM results, the Kerrisk method and a regression analysis method developed by Murugan et al. (referred to as the LRM here) perform the best. Six railgun force computation methods are investigated, including the traditional railgun force equation, an equation produced by Waindok and Piekielny, and four methods inspired by the work of Xu et al. Overall, good agreement between the models and outside data is found, but each model&rsquo;s accuracy varies significantly between comparisons. Lastly, an approximation of the temperature profile in railgun rails originally presented by McCorkle and Bahder is replicated. In total, this work describes railgun technology and moderately complex railgun modeling methods, but is inconclusive about the presence of a middle-ground modeling method.</p><p>

abstract: Standard procedures to estimate en-route aircraft performance rely upon the “standard atmosphere”. Real-world conditions are then represented as deviations from the standard atmosphere. Both flight manuals and aircraft designers make heavy use of the “deviation method” to account for geographical and temperature differences in atmospheric conditions. This method is often done statically, choosing a single deviation based on temperature and a single wind speed for the duration of an entire mission. Real-world atmospheric conditions have an incredible amount of variation throughout any given flight route, however. Changes in geographic location can present many changes within the atmosphere; they include differences in air temperature, humidity, wind speeds, wind directions, air densities, and more. Historically, these changes have not been accounted for in standard mission performance models. However, they present major possible impacts on real missions. This thesis addresses this issue by developing a lateral and vertical mission simulation method that uses real-world and up-to-date atmospheric conditions to determine the effect of changing atmospheric conditions on en-route performance and economy. The custom toolset was used in combination with a series of trades over a series of five days and a representation of each season to show the variation that occurs on a single route over the course of daily and seasonal periods. Both qualitative and quantitative effects from this perspective were recorded for the Airbus A320 and a student designed regional jet, the Aeris, to determine the effect of atmospheric variation on standard commercial transport and hypothetical high-altitude capable commercial transport. The variance presented by changing atmospheric conditions is massive and has large implications on future aircraft operations and design. Due to large geographical and temporal variation in the wind speeds and directions, it is recommended that aircraft operators use daily measurements of atmospheric conditions to determine optimal flight paths and altitudes. Further investigation is recommended in terms of the effect of changing atmosphere for design, however from initial investigations it appears that a statistical method works well for incorporating the large variance added by real-world conditions. / Dissertation/Thesis / Masters Thesis Aerospace Engineering 2019

The leading edge slat of a high-lift system is known to be a large contributor to the overall radiated acoustic field from an aircraft during the approach phase of the flight path. This is due to the unsteady flow field generated in the slat-cove and near the leading edge of the main element. In an effort to understand the characteristics of the flow-induced source mechanisms, a suite of experimental measurements has been performed on a two-dimensional multi-element airfoil, namely, the MD-30P30N. Particle image velocimetry provide mean flow field and turbulence statistics to illustrate the differences associated with a change in angle of attack. Phase-averaged quantities prove shear layer instabilities to be linked to narrowband peaks found in the acoustic spectrum. Unsteady surface pressure are also acquired, displaying strong narrowband peaks and large spanwise coherence at low angles of attack, whereas the spectrum becomes predominately broadband at high angles. Nonlinear frequency interaction is found to occur at low angles of attack, while being negligible at high angles. To localize and quantify the noise sources, phased microphone array measurements are per- formed on the two dimensional high-lift configuration. A Kevlar wall test section is utilized to allow the mean aerodynamic flow field to approach distributions similar to a free-air configuration, while still capable of measuring the far field acoustic signature. However, the inclusion of elastic porous sidewalls alters both aerodynamic and acoustic characteristics. Such effects are considered and accounted for. Integrated spectra from Delay and Sum and DAMAS beamforming effectively suppress background facility noise and additional noise generated at the tunnel wall/airfoil junction. Finally, temporally-resolved estimates of a low-dimensional representation of the velocity vector fields are obtained through the use of proper orthogonal decomposition and spectral linear stochastic estimation. An estimate of the pressure field is then extracted by Poissons equation. From this, Curles analogy projects the time-resolved pressure forces on the airfoil surface to further establish the connection between the dominating unsteady flow structures and the propagated noise. / A Dissertation submitted to the Department of Mechanical Engineering in partial fulfillment of the requirements for the degree of Doctor of Philosophy. / Spring Semester 2017. / March 30, 2017. / 30P30N, Aeroacoustics, High-Lift, Kevlar, Slat Noise, Wind Tunnel / Includes bibliographical references. / Louis Cattafesta, Professor Directing Dissertation; Mark Sussman, University Representative; Farrukh Alvi, Committee Member; Chengying Xu, Committee Member; Meelan Choudhari, Committee Member.

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