Aerospace Engineering Commons^™

Utilization Of Characteristic Modal Analysis For Antenna Design Needed For An Afit Satellite, Scott C. Podlogar

Theses and Dissertations

Antenna design is a pervasive, growing field for electrical engineers. As the number of new materials and techniques increase so too does the demand and requirements pushing forth new innovative ideas. Among these ideas is a leading edge analytic technique called Characteristic Modal Analysis (CMA) originally credited to Garbacz and Turpin. CMA works to break down the current distribution along a structure in a way that can offer great insights into how that structure operates as an antenna. This technique has great merits in post design analytics but it is rarely seen to be integrated into the design process. This …

Magnetic Anomaly Absolute Positioning For Hypersonic Aircraft, Alexander J. Mcneil

Theses and Dissertations

GPS has proven to be an extremely valuable asset for navigation, and timing. GPS has become the standard navigation system for all applications, but GPS has limitations. GPS is susceptible to jamming, spoofing, and in the case of hypersonic aircraft, is likely unavailable. When an aircraft is traveling at hypersonic speeds, there is a plasma sheath that surrounds the aircraft. This plasma sheath blocks electromagnetic waves, and is therefore responsible for a GPS blackout. GPS unavailability for hypersonic aircraft has prompted the research into the viability of alternate navigation systems for these aircraft. This paper seeks to explore the viability …

Estimating Atmospheric Turbulence Within A Short Exposure Frame Selection Algorithm, Aaron J. Deluca

Theses and Dissertations

Space is becoming an increasingly crowded domain. As it becomes more congested, the ability to accurately detect and track objects, both natural and man-made, becomes more and more important. Having an accurate space surveillance network allows us to protect our own space assets while also maintaining awareness of foreign space assets and threats to our satellites such as debris and small meteorites. This means that the ability to detect small, dim objects is key to being able to protect our space assets. This thesis will seek to expand on and improve certain existing space object detection techniques and algorithms.

A Proposed Mission Assurance Framework For University Cubesat Programs, Mitchell R. Thomas

Theses and Dissertations

The low cost, small form factor, and use of Commercial-Off-The-Shelf components make CubeSats an ideal platform for university use given their unique constraints. Since 2000, roughly 55% of CubeSats developed by universities fail to meet mission goals. Mission assurance, which is used to increase confidence in mission success, is based around traditional government programs, and does not provide an adequate road map for universities. Leaving them without specific guidance in tailoring mission assurance activities to operate within their constraints. This paper adapts these traditional practices to develop a baseline mission assurance framework for university CubeSat programs.

Coupled Orbit-Attitude Dynamics And Control Of A Cubesat Equipped With A Robotic Manipulator, Charles M. Carr

Theses and Dissertations

This research investigates the utility and expected performance of a robotic servicing CubeSat. The coupled orbit-attitude dynamics of a 6U CubeSat equipped with a four-link serial manipulator are derived. A proportional-integral-derivative controller is implemented to guide the robot through a series of orbital scenarios, including rendezvous and docking following ejection from a chief spacecraft, repositioning the end effector to a desired location, and tracing a desired path with the end effector. Various techniques involving path planning and inverse differential kinematics are leveraged. Simulation results are presented and performance metrics such as settling time, state errors, control use, and system robustness …

Aeroelasticity Of Six Degree-Of-Freedom Satellite Bus Configurations During Terminal Reentry, Jinhee F. Byun

Theses and Dissertations

With disposable equipment on board, the emphasis on structural strength and robust thermal protection system (TPS) pales for a conventional satellite in comparison to reentry capsules, which are specifically designed to withstand the intense aerothermodynamic effects experienced during reentry. In this research, six degree-of-freedom (6DOF) analyses of three distinct non-aerodynamic satellite bus configurations were performed with emphasis on the investigation of their terminal reentry characteristics, and thermal and deceleration loading on the satellite body. Aeroelastic effects on their respective solar panel structures were also analyzed focusing on characterizing bending stress at their attachment/deployment mechanism. It was found that the Terra …

Differential Game-Based Defensive Architecture Study Employing Ground-Based Interceptors, Stephen T. Zittrouer

Theses and Dissertations

A study of defensive architectures for combating hypersonic glide vehicles (HGVs) via interception with a ground-based interceptor (GBI) is presented. Pursuit-evasion differential games are formulated for numerical simulation of the interception engagements. A one-sided optimal control problem wherein the evader HGV is optimized and the pursuer GBI employs a suboptimal proportional navigation control strategy is solved. The solution space is characterized by varying the pursuer initial velocity advantage relative to the evader. A two-sided optimal control problem in which both players behave optimally is solved via the semi-direct collocation with nonlinear programming (semiDCNLP) method. The resulting state and control trajectories …

Pedagogical Approaches For Facilitating Engineering Leadership Development, Teresa J. Didiano, Annie E. Simpson, David J. Bayless

Mechanical and Aerospace Engineering Faculty Research & Creative Works

This article describes transformative, impactful pedagogical practices that engage students in the process of leadership development. We share practical examples of instructional strategies and facilitation techniques from curricular and co-curricular initiatives.

Experimental Study Of Turbulent Flow Heat Transfer And Pressure Loss Over Surfaces With Dense Micro-Depth Dimples Under Viscous Sublayer, Peng Zhang, Yu Rao, Phillip M. Ligrani

PRC-Affiliated Research

Presented are experimentally-measured heat transfer and pressure loss characteristics for dimpled surfaces, placed along one surface of a channel, with different ratios of dimple depth to channel height δ/H, and for Reynolds numbers ranging from 10,000 to 70,000. With the same relative dimple spacing to dimple print diameter, and the same ratio of dimple depth to dimple print diameter of δ/d = 0.20, experimental results for arrays of spherical indentation dimples with micro depths of δ = 0.6 and 1.0 mm (δ/H = 0.03 and 0.05) are compared with thermal characteristics for arrays of larger dimples with δ = 4.0 …

Effect Of Processing Parameters And Build Orientation On Microstructure And Performance Of Aisi Stainless Steel 304l Made With Selective Laser Melting Under Different Strain Rates, Tan Pan, Xinchang Zhang, Aaron Flood, Sreekar Karnati, Wei Li, Joseph William Newkirk, Frank W. Liou

Materials Science and Engineering Faculty Research & Creative Works

Selective laser melting (SLM) process allows greater geometry flexibility; therefore, it has become more widespread in its deployment in the industry for fabricating metal alloys. However, a material characterization study is needed in order to understand better the correlation between the process, microstructure, and performance. In the current study, the raw SLM fabricated AISI stainless steel 304 L was fabricated with different processing parameters and build orientations (horizontal, inclined, and vertical). The tensile behavior was evaluated under different strain rates (0.0001/s, 0.001/s, 0.01/s, and 0.1/s) and then compared to commercial cold-rolled and annealed counterparts. Grain structures, tensile strength, elongation-to-failure, strain …

Six-Bar Linkage Models Of A Recumbent Tricycle Mechanism To Increase Power Throughput In Fes Cycling, Nicholas A. Lanese, David H. Myszka, Anthony L. Bazler, Andrew P. Murray

Mechanical and Aerospace Engineering Faculty Publications

This paper presents the kinematic and static analysis of two mechanisms to improve power throughput for persons with tetra- or paraplegia pedaling a performance tricycle via FES. FES, or functional electrical stimulation, activates muscles by passing small electrical currents through the muscle creating a contraction. The use of FES can build muscle in patients, relieve soreness, and promote cardiovascular health. Compared to an able-bodied rider, a cyclist stimulated via FES produces an order of magnitude less power creating some notable pedaling difficulties especially pertaining to inactive zones. An inactive zone occurs when the leg position is unable to produce enough …

Developing Metrics For Nasa Earth Science Interdisciplinary Data Products And Services, Zhong Liu, Chung-Lin Shie, Anthony J. Ritrivi, Guang-Dih Lei, Gary T. Alcott, Mary Greene, James Acker, Jennifer C. Wei, David J. Meyer, Angela Li, Atheer F. Al-Jazrawi

Copyright, Fair Use, Scholarly Communication, etc.

Metrics are measures that are able to produce quantifiable information. There are many applications of metrics in Earth science data and services; for example, metrics are frequently used to track service performance and progress. In short, developing, collecting and analyzing metrics are essential activities to better support Earth science research, applications, and education.

As one of the largest repositories of Earth science data in the world, NASA’s Earth Science Data and Information System (ESDIS) Project supports twelve Distributed Active Archive Centers (DAACs). Standard metrics have been developed by the ESDIS Metrics System (EMS). These metrics are collected and analyzed routinely …

Flow And Heat Transfer Characteristics In A Pre-Swirl Rotor-Stator Cavity, Xiaoyu Yang, Zhong Ren, Jing Ren, Philip M. Ligrani

PRC-Affiliated Research

The present study investigates flow and heat transfer characteristics in a rotor-stator pre-swirl system. Considered are rotational Reynolds numbers ReФ ranging from 3.4 × 105 to 6.8 × 105, with jet Reynolds numbers Rew of approximately 8.8 × 104 to 3.81 × 105, and associated turbulent flow parameter λT = Cw/ReФ0.8 varying from 0 to 0.4. Experimentally-measured and numerically-predicted results illustrate the combined and separate influences of jet impingement and rotor entrainment, as they affect and govern flow and heat transfer characteristics within the cavity. These results show that the relative strength of the two effects varies with ReФ and …

Flow Structure And Surface Heat Transfer From Numerical Predictions For A Double Wall Effusion Plate With Impingement Jet Array Cooling, Hwabhin Kwon, Phillip M. Ligrani, Sneha Reddy Vanga, Heesung Park

PRC-Affiliated Research

To provide additional understanding of double wall cooling arrangements, especially local distributions of flow properties which are responsible for hot-side surface and cold-side surface heat transfer variations, investigated are numerically-simulated distributions of turbulent flow structural characteristics. Also considered are numerically-simulated surface heat transfer characteristics, including comparisons with experimentally-measured distributions. The numerical results are obtained using the ANSYS FLUENT Version 19.1 numerical code, with a k-ω SST turbulence model. The present arrangement includes a full-coverage effusion cooling plate, with coolant initially supplied by an impingement jet array. Considered are the effects of effusion blowing ratio, impingement jet Reynolds number, and streamwise …

Data On The Validation To Determine The Material Thermal Properties Estimation Via A One-Dimensional Transient Convection Model, Lauren B. Tomanek, Daniel S. Stutts

Mechanical and Aerospace Engineering Faculty Research & Creative Works

These data were acquired to estimate the parameters of a closed form solution of a one-dimensional transient convection heat diffusion PDE. The purpose was to demonstrate that the model could be used to determine the thermal conductivity. The system was tested for a wide range of thermal conductivity, 15-400 W/mK, in order to verify that the method was applicable for various materials. The data reported here refer to the study in the research articles, "Material Thermal Properties Estimation Via a One-Dimensional Transient Convection Model" [1] and "Influence of porosity on the thermal, electrical, and mechanical performance of selective laser melted …

Effects Of Particle Size Distribution With Efficient Packing On Powder Flowability And Selective Laser Melting Process, Zachary Young, Minglei Qu, Meelap Michael Coday, Qilin Guo, Seyed Mohammad H. Hojjatzadeh, Luis I. Escano, Kamel Fezzaa, Lianyi Chen

Mechanical and Aerospace Engineering Faculty Research & Creative Works

The powder bed-based additive manufacturing (AM) process contains uncertainties in the powder spreading process and powder bed quality, leading to problems in repeatability and quality of the additively manufactured parts. This work focuses on identifying the uncertainty induced by particle size distribution (PSD) on powder flowability and the laser melting process, using Ti6Al4V as a model material. The flowability test results show that the effect of PSDs on flowability is not linear, rather the PSDs near dense packing ratios cause significant reductions in flowability (indicated by the increase in the avalanche angle and break energy of the powders measured by …

Characterization, Design, And Optimization Of Dual-Purpose Wind Turbines And Frost Protection Fans, Ethan Narad

Master's Theses

This thesis report outlines the creation of a MATLAB tool to design reversible machines that can function as both wind turbines and as agricultural frost protection fans. Frost protection fans are used to prevent crop loss during radiative freeze events during which a temperature inversion is present. Such a dual-purpose machine fundamentally has the constraint that it must use symmetric airfoils, so a suite of tools for automatically designing an optimized wind turbine blade with symmetric airfoils using the Blade Element Momentum (BEM) theory approach is presented. The BEM code is then re-derived and adapted for use with a frost …

Robust Error Estimation Based On Factor-Graph Models For Non-Line-Of-Sight Localization, O. Arda Vanli, Clark N. Taylor

Faculty Publications

This paper presents a method to estimate the covariances of the inputs in a factor-graph formulation for localization under non-line-of-sight conditions. A general solution based on covariance estimation and M-estimators in linear regression problems, is presented that is shown to give unbiased estimators of multiple variances and are robust against outliers. An iteratively re-weighted least squares algorithm is proposed to jointly compute the proposed variance estimators and the state estimates for the nonlinear factor graph optimization. The efficacy of the method is illustrated in a simulation study using a robot localization problem under various process and measurement models and measurement …

Eye-Gaze-Controlled Hmds And Mfd For Military Aircraft, Lrd Murthy, Abhishek Mukhopadhyay, Somnath Arjun, Varshith Yelleti, Peter Thomas, Dilli Babu Mohan, Pradipta Biswas

Journal of Aviation Technology and Engineering

Eye-gaze-controlled interfaces allow the direct manipulation of a graphical user interface by looking at it. This technology has great potential in military aviation, in particular, operating different displays in situations where pilots’ hands are occupied with flying the aircraft. This paper reports studies on analyzing the accuracy of eye-gaze-controlled interfaces inside aircraft undertaking representative flying missions. We report that using eye-gaze-controlled interfaces, pilots can undertake representative pointing and selection tasks at less than two seconds on average in a transport aircraft. Further, we analyzed the accuracy of eye-gaze-tracking glasses under various G load factors and analyzed the failure modes. We …

Characterization Of Effective Diffusion Within Viscoelastic Fluids With Elastic Instabilities, Valerie Hietsch, Phillip Ligrani, Mengying Su

PRC-Affiliated Research

We considered effective diffusion, characterized by magnitudes of effective diffusion coefficients, in order to quantify mass transport due to the onset and development of elastic instabilities. Effective diffusion coefficient magnitudes were determined using different analytic approaches, as they were applied to tracked visualizations of fluorescein dye front variations, as circumferential advection was imposed upon a flow environment produced using a rotating Couette flow arrangement. Effective diffusion coefficient results were provided for a range of flow shear rates, which were produced using different Couette flow rotation speeds and two different flow environment fluid depths. To visualize the flow behavior within the …