Aerospace Engineering Commons^™

Direct Position Control Of Dielectric Barrier Discharge Filaments, Matthew C. Paliwoda, Joshua L. Rovey, Mitchell Wainwright

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Controllable patterns of plasma filaments are being explored for reconfigurable metamaterial applications. When operated in a filamentary mode, volume dielectric barrier discharges are known to produce patterns of self-organizing plasma filaments. In this work the presence and intensity of a single filament at a fixed location is controlled by an isolated and independently electrically adjusted needle electrode. Time-averaged normalized light intensity, current, and voltage are measured while varying the voltage of the needle through a self-biasing resistance. For a 7.5 kV, 3.2 kHz DBD, the needle-controlled filament discharges similar to adjacent filaments at low potentials but stops discharging at a …

Observation Of Late-Time Ablation In Electric Solid Propellant Pulsed Microthrusters, Matthew S. Glascock, Joshua L. Rovey, Shae Williams, Jason Thrasher

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Electric solid propellants are an interesting potential option for propulsion because they are ignited by an applied electric current. The electric nature of these materials leads to the capability for use in pulsed electric propulsion devices. In this work, the ablation process of an electric solid propellant during pulsed micro thruster operation is investigated using a triple Langmuir probe, thrust stand and high-speed video camera. Results include quantitative time-of-flight, ablation mass per pulse and impulse-per-pulse measurements. Additionally, qualitative images from the high-speed video are temporally correlated to these measurements. Analyses indicate 45±11% of the ablated mass per pulse is expelled …

Mass Spectrometry Of Selected Ionic Liquids In Capillary Electrospray At Nanoliter Volumetric Flow Rates, Shawn W. Miller, Benjamin D. Prince, Raymond J. Bemish, Joshua L. Rovey

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Capillary-based electrospray thrusters allow user-enabled control of the volumetric flow rate of the propellant. This control, coupled with mass spectrometry techniques spanning a large mass-to-charge range, enables elucidation of the composition of the electrospray beam and through further analyses, a better understanding of the physics occurring at the liquid/vacuum interface. In this work, mass spectra of selected ionic liquids electro sprayed from a capillary emitter are measured, using time-of-flight mass spectrometry, over a wide range of volumetric flow rates. The time-of-flight mass spectrometer enables simultaneous acquisition over a mass-to-charge range of 20 amu/q to ~500,000 amu/q in a single pulse …

Comparison Of Robust And Probabilistic Lmi-Based Design Of Adaptive Flight Controllers With Uncertain Input Dynamics, Mario Luca Fravolini, Tansel Yucelen, Benjamin Gruenwald, Merve Dogan, Marcello R. Napolitano

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Adaptive control-based schemes have been implemented to date in a variety of different ap-plications. However, the ability to obtain a predictable transient closed-loop performance in adaptive systems is still a challenging problem from a verification and validation point of view. To face this problem we have recently introduced an analysis and design framework for adaptive control systems in the presence of bounded uncertainty and bounded adaptive control (the boundedness can be enforced, for instance, by a parameter projection mechanism) showing that the transitory performance of a MRAC system can be expressed, analyzed, and optimized via a convex optimization formulation based …

Silicon-Wall Interfacial Free Energy Via Thermodynamics Integration, Wan Shou, Heng Pan

Mechanical and Aerospace Engineering Faculty Research & Creative Works

We compute the interfacial free energy of a silicon system in contact with flat and structured walls by molecular dynamics simulation. The thermodynamics integration method, previously applied to Lennard-Jones potentials [R. Benjamin and J. Horbach, J. Chem. Phys. 137, 044707 (2012)], has been extended and implemented in Tersoff potentials with two-body and three-body interactions taken into consideration. The thermodynamic integration scheme includes two steps. In the first step, the bulk Tersoff system is reversibly transformed to a state where it interacts with a structureless flat wall, and in a second step, the flat structureless wall is reversibly transformed into an …

Design Optimization Of Sandwich Core, Mohammad Tauhiduzzaman

Open Access Theses & Dissertations

Ultralight sandwich structures comprising of low-density core with stiff facings have attracted significant research interest for their considerable weight saving applications. The aircraft industries are focusing on decreasing the structural mass to lower the manufacturing and operating costs. Design analysis of the sandwich cores using finite element analysis has been developed as a promising concept to feature sandwich structures with maximum strength, stiffness, and reduced weight. To obtain multifunctional behavior of sandwich panels, a profound investigation of geometrical and mechanical properties in the transverse plane is required because it is very susceptible to any kind loadings. Structural optimization is one …

Design Of A 500 Lbf Liquid Oxygen And Liquid Methane Rocket Engine For Suborbital Flight, Jesus Eduardo Trillo

Open Access Theses & Dissertations

Liquid methane (LCH4)is the most promising rocket fuel for our journey to Mars and other space entities. Compared to liquid hydrogen, the most common cryogenic fuel used today, methane is denser and can be stored at a more manageable temperature; leading to more affordable tanks and a lighter system. The most important advantage is it can be produced from local sources using in-situ resource utilization (ISRU) technology. This will allow the production of the fuel needed to come back to earth on the surface of Mars, or the space entity being explored,making the overall mission more cost effective by enabling …

Computational Modeling Of A 60kw Oxy-Methane Direct Power Extraction Combustor, Omar Daniel Vidana

Open Access Theses & Dissertations

ANSYS Fluent was used to optimize components of a direct power extraction combustor. This includes the fuel injector, nozzle, and cooling units. Changes in the injector's inlet location impacted pressure and velocity distribution. An angle of 115 degrees with respect to the x-axis was found to increase distribution efficiency. Temperature and velocity data from the combustor and nozzle were calculated using NASA CEA and Fluent. Magnitudes of temperature and velocity for CEA and Fluent matched within 9% and 4%, respectively. For the cooling system it is expected that cavitation will not occur since the saturation temperature of water is not …

Structural Health Monitoring Of Composite Overwrapped Pressure Vessels, Luca Letizia

Honors Undergraduate Theses

This work is focusing to study the structural behavior of Composite Overwrapped Pressure Vessels (COPVs). These COPVs are found in many engineering applications. In the aerospace field, they are installed onto spaceships and aid the reorientation of the spacecraft in very far and airless, therefore frictionless, orbits to save energy and fuel. The intent of this research is to analyze the difference in performance of both perfectly intact and purposely damaged tanks. Understanding both the source and location of a structural fault will help NASA engineers predict the performance of COPVs subject to similar conditions, which could prevent failures of …

Smart Material Actuation And Morphing For Unmanned Aircraft Systems, Caio H. Da Silva Lima

Honors Undergraduate Theses

The intent of this thesis is to outline the design, analysis, and characterization of an axially compressed piezocomposite actuator and, in particular, to determine the correlation and accuracy of two models used to predict deflection of an axially compressed piezocomposite bimorph. Restrictions in material properties lead to vehicle inefficiencies caused by the discontinuous geometry of deflected control surfaces in unmanned aircraft systems. This performance disadvantage in discrete control surfaces is caused in part by the sharp edges that are formed when the surface is pivoted. Flow continuity over the body of a vehicle is important in minimizing the effects of …

An Experimental Investigation Of Heat Transfer For Arrays Of Impingement Jets Onto The Featured Surfaces With Cylindrical And Elliptical Raised Surfaces, Marc A. Medina

Honors Undergraduate Theses

This study focuses on multi-jet impingement for gas turbine geometries in which the objective is to understand the influence of the roughness elements on a target surface to the heat transfer. Current work has proven that implementing roughness elements for multi-jet impingement target surfaces has increased heat transfer ranging anywhere from 10-30%. This study has chosen to investigate three different roughness elements, elliptical in cross-section, to compare to smooth surface geometries for multi-jet impingement. An experimental was taken for this study to extend the current knowledge of multi-jet impingement geometries and to further understand the heat transfer performance. A temperature …

Conjugate Heat Transfer Analysis Of Combined Regenerative And Discrete Film Cooling In A Rocket Nozzle, Charlotte M. Pearce

Honors Undergraduate Theses

Conjugate heat transfer analysis has been carried out on an 89kN thrust chamber in order to evaluate whether combined discrete film cooling and regenerative cooling in a rocket nozzle is feasible. Several cooling configurations were tested against a baseline design of regenerative cooling only. New designs include combined cooling channels with one row of discrete film cooling holes near the throat of the nozzle, and turbulated cooling channels combined with a row of discrete film cooling holes. Blowing ratio and channel mass flow rate were both varied for each design. The effectiveness of each configuration was measured via the maximum …

Characterization Of Dispersion And Residual Stress In Nanoparticle Reinforced Hybrid Carbon Fiber Composites, Alex Selimov

Honors Undergraduate Theses

Hybrid carbon fiber reinforced composites are a new breed of materials that are currently being explored and characterized for next generation aerospace applications. Through the introduction of secondary reinforcements, such as alumina nanoparticles, hybrid properties including improved mechanical properties and stress sensing capabilities can be achieved. In order to maximize these properties, it is necessary to achieve a homogeneous dispersion of particulate filler. Utilizing the photoluminescent properties of alumina, it is possible to compare local levels of particle concentration through emission intensities as a way to determine the effectiveness of the tested manufacturing parameters in increasing material homogeneity. Parameters of …

Geometric Consideration Of Nanostructures For Energy Storage Systems, Jonghyun Park, Jie Li, Wei Lu, Ann Marie Sastry

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Battery performance and its fade are determined by various aspects such as the transport of ions and electrons through heterogeneous internal structures; kinetic reactions at the interfaces; and the corresponding interplay between mechanical, chemical, and thermal responses. The fundamental factor determining this complex multiscale and multiphysical nature of a battery is the geometry of active materials. In this work, we systematically consider the tradeoffs among a selection of limiting geometries of media designed to store ions or other species via a diffusion process. Specifically, we begin the investigation by considering diffusion in spheres, rods, and plates at the particle level, …

Ionic And Electronic Conductivities Of Atomic Layer Deposition Thin Film Coated Lithium Ion Battery Cathode Particles, Rajankumar L. Patel, Jonghyun Park, Xinhua Liang

Mechanical and Aerospace Engineering Faculty Research & Creative Works

It is imperative to ascertain the ionic and electronic components of the total conductivity of an electrochemically active material. A blocking technique, called the “Hebb-Wagner method”, is normally used to explain the two components (ionic and electronic) of a mixed conductor, in combination with the complex ac impedance method and dc polarization measurements. CeO₂ atomic layer deposition (ALD)-coated and uncoated, LiMn₂O₄ (LMO) and LiMn_1.5Ni_0.5O₄ (LMNO) powders were pressed into pellets and then painted with silver to act as a blocking electrode. The electronic conductivities were derived from the currents obtained using …

Cryogenic Processing Of Al 7050-T7451 Alloy For Improved Surface Integrity, Bo Huang

Theses and Dissertations--Mechanical and Aerospace Engineering

Al 7050-T7451 alloy with good combinations of strength, stress corrosion cracking resistance and toughness, is used broadly in the aerospace/aviation industry for fatigue-critical airframe structural components. However, it is also considered as a highly anisotropic alloy as the crack growth behavior along the short transverse direction is very different from the one in the long transverse direction, due to the inhomogeneous microstructure with the elongated grains distributed in the work material used in the sheet/plate applications. Further processes on these materials are needed to improve its mechanical and material properties and broaden its applications.

The material with ultra-fine or nano …

Comparisons Of Ablator Experimental Performance To Response Modeling And Effects Of Water Phase Transition In Porous Tps Materials, David L. Smith

Theses and Dissertations--Mechanical and Aerospace Engineering

The Mars Science Laboratory Entry Descent and Landing Instrumentation (MEDLI) project performed extensive arc jet tests for development, qualification, and calibration of instrumented heat shield plugs. These plugs each contained several thermocouples for recording near-surface and in-depth temperature response of the Phenolic Impregnated Carbon Ablator (PICA) heat shield. The arc jet test results are entered into a comprehensive database so that broad trends across the test series can be compared. One method of analysis is to compare with ablator material response calculations and solve the in-depth heat conduction equations. Using the near-surface thermocouple measurements as a boundary condition in numerical …

High Temperature Shock Tube Ignition Studies Of Co2 Diluted Mixtures, Owen Pryor

Electronic Theses and Dissertations

Energy demand is expected to grow by 20% over the next 10 years. In order to account for this increase in energy consumption new and novel combustion techniques are required to mitigate the effects of pollution and fossil fuel dependency. Oxy-fuel combustion in supercritical carbon dioxide (sCO2) cycles can increase plant efficiencies up to 52% and reduce pollutants such as NOX and CO2 by 99%. Supercritical engine cycles have demonstrated electricity costs of $121/MWh, which is competitive in comparison to conventional coal ($95.60/MWh) and natural gas power plants ($128.4/MWe). This increase in efficiency is mainly driven by the near-liquid density …

Approximated Control Affine Dynamics Mode For An Agricultural Field Robot Considering Wheel Terrain Interaction, Pablo Menendez-Aponte

Electronic Theses and Dissertations

As populations and the demand for higher crop yields grow, so to does the need for efficient agricultural wheeled mobile robots. To achieve precise navigation through a field it is desirable that the control system is designed based on an accurate dynamic model. In this paper a control affine model for a custom designed skid-steer differential drive wheeled mobile robot is found. The Terramechanic wheel terrain interaction is adopted and modified to consider wheels with a torus geometry. Varying slip ratios and slip angles are considered in the terrain reaction forces, which is curve-fitted using a nonlinear least squares approach …

Kinematical Modelling And Its Analytical Inverse Kinematic Solution For The Handling Mechanism Of An Agricultural Robot, Sinem Gozde Defterli

Electronic Theses and Dissertations

Early detection of the crop diseases helps to prevent failure in the amount and the quality of the production. In agricultural robotics, the idea of a disease detection robot is a fresh and an innovative hot-button topic. The exclusion of the diseased parts from the strawberry plants for further analyses is one of the main tasks of a recently developed strawberry robot. To this purpose, the handling mechanism in the robot needs to achieve an accurate manipulation task to reach the target. Reaching, cutting and storing the diseased leaf are challenging and delicate processes during the procedure of the handling …