Engineering Commons^™

Polyacrylonitrile Copolymers: Effects Of Molecular Weight, Polydispersity, Composition, And Sequencing On Thermal Ring-Closing Stabilization, Jeremy D. Moskowitz

Dissertations

Controlled polyacrylonitrile (PAN)-based carbon fiber precursors with defined molecular weights, polydispersities, compositions, and architectures have been prepared for their study on thermal ring-closing stabilization behavior. PAN and its copolymers of number average molecular weights exceeding 170,000 g/mol were successfully synthesized via low temperature reversible addition-fragmentation chain transfer (RAFT) polymerization. RAFT polymerizations of PAN-based precursors were compared to conventional free radical solution polymerizations with a focus on the effects of molecular weight and polydispersity on structural evolution and cyclization efficiency. When RAFT polymerization was extended to copolymers, it was found that RAFT copolymers achieved greater cyclization intensities and improved thermal stability …

The Impact Of Crystal Morphology On The Thermal Responses Of Ultrasonically-Excited Energetic Materials, J. K. Miller, J. O. Mares, I. E. Gunduz, Steven F. Son, Jeff Rhoads

Purdue Energetics Research Center Articles

The ability to detect explosive materials may be significantly enhanced with local increases in vapor pressure caused by an elevation of the materials'temperature. Recently, ultrasonic excitation has been shown to generate heat within plastic-bonded energetic materials. To investigate the impact of crystal morphology on this heating, samples of elastic binder are implanted with single ammonium perchlorate crystals of two distinct shape groups. Contact piezoelectric transducers are then used to excite the samples at ultrasonicfrequencies. The thermal responses of the crystals are recorded using infrared thermography, and the rate of heating is estimated. Surface temperature increases up to 15 °C …

Direct Adaptive Control For Stability And Command Augmentation System Of An Air-Breathing Hypersonic Vehicle, Ron Aditya

Doctoral Dissertations and Master's Theses

In this paper we explore a Direct Adaptive Control scheme for stabilizing a non-linear, physics based model of the longitudinal dynamics for an air breathing hypersonic vehicle. The model, derived from first principles, captures the complex interactions between the propulsion system, aerodynamics, and structural dynamics. The linearized aircraft dynamics show unstable and non-minimum phase behavior. It also shows a strong short period coupling with the fuselage-bending mode. The value added by direct adaptive control and the theoretical requirements for stable convergent operation is displayed. One of the main benefits of the Directive Adaptive Control is that it can be implemented …

Implementing A Linear Quadratic Spacecraft Attitude Control System, Daniel Kolosa

Masters Theses

This thesis implements a linear quadratic attitude control system for a low-thrust spacecraft. The goal is to maintain spacecraft alignment with a time-varying thrust vector needed for trajectory change maneuvers. A linear quadratic attitude control approach is used to maintain spacecraft pointing throughout flight. This attitude control strategy uses the thrust-acceleration input obtained from a linear quadratic optimal trajectory control model that simulates the trajectory of a spacecraft in orbit maneuvers. This attitude model simulates a CubeSat, a small satellite that is equipped with a low-thrust propulsion and attitude control system. An orbit raising and a plane change scenario is …

Aerodynamic Trade Study Of Compound Helicopter Concepts, Julian Roche

Doctoral Dissertations and Master's Theses

The relative performance attributes of compound helicopter concepts have been examined, including their potential for meeting the requirements of several challenging mission profiles. For each concept, which included lift and/or propulsive compounding, a suite of aerodynamic performance models was developed using energy methods. In the case of a lift-compounded concept, an aerodynamic model representing the force interaction effects of the main rotor wake with the wing was also developed. Models of a conventional helicopter and of a tiltrotor were implemented as well, and the results used as a datum for comparison. In each case, the predictive capabilities of the model …

An Investigation Of Cooling Configurations In Gas Turbine Engines Using Jet Impingement, Bhushan Upalkar

Doctoral Dissertations and Master's Theses

A numerical investigation for predicting the heat transfer effects of turbulence was conducted by making a scaled-up model of a section in a jet impingement channel. Different turbulence models were run and the results were compared to experimental data. Experimental comparisons were made for impingement channels between a baseline case, which is a rectangular array of jets of 20 rows and 3 jets per row, and different hole spacing configurations. The heat transfer was measured using Temperature Sensitive Paint. The turbulence model v²-f gave the most accurate prediction with an error of about 17% with the EB k-E, with an …

Low-Velocity Impact Analysis Of Composite Repair Patches Of Different Shapes, Sarvesh Baliga

Doctoral Dissertations and Master's Theses

The area under crack for various structures can be effectively repaired by the use of composite materials. Low velocity impact can cause barely visible damage to the interior structure of laminated composite. These impacts can cause delamination in composite materials. In this study, a Finite Element Analysis was conducted using Abaqus/Explicit and the results of the analysis were compared to the experimental data from literature. E-glass/epoxy composite laminate was subjected to a low velocity impact test. To study the effect of patch repair, a composite patch was applied on a cracked laminate and a low velocity impact was then conducted …

Experimental And Computational Investigation Of Ribbed Channels For Gas Turbine Thermal Management, Yash T. Mehta

Doctoral Dissertations and Master's Theses

This study focuses on the computational benchmarking as well as validation against experimental results of a rib roughed surface in an internal channel of a stationary turbine blade. STAR-CCM+ was utilized to replace a model from a published article, and to analyze the CFD conjugate heat transfer by determining the turbulence model that best matched the published experimental values. Using those computational conditions and CFD results, an in house experimental rig was validated by comparing convective heat transfer coefficients and pressure profiles. This cooling method, when compared to a smooth channel, enhances turbulent mixing my separating and reattaching the boundary …

Lagrangian Points And Jacobi Constants For A Class Of Asteroids, Tasneem Rashid

Doctoral Dissertations and Master's Theses

Asteroid Gravitational Potentials are difficult to model owing to their irregularity in shape. This thesis focuses on two approaches to model asteroid gravity fields, namely, multiple-body and spherical harmonics modeling. Computation of gravity potential serves as a first step to determine equilibrium points called Lagrangian points for a spacecraft orbiting as an asteroid. Further, Jacobi analysis is carried out to determine zero-velocity regions, i.e., inaccessible regions corresponding to the unstable Lagrangian points. Multiple sphere modeling was studied through analysis of so called Asteroid Restricted Three and Four Body Problems, providing insight into the method of modeling an asteroid as a …

Design, Fabrication, And Testing Of A Proprioceptive Electroadhesion Pad For Space Applications, Walter Saravia

Doctoral Dissertations and Master's Theses

The purpose of this study is to design, analyze, and fabricate an electroadhesion mechanism with the goal of providing controlled electrostatic adhesion to objects with little known surface finish, of varying curvature, and different materials. The main purpose of the mechanism is that of ensuring a soft docking, controlled in closed loop, for attachment to large pieces of orbital debris. Other envisaged purposes for the mechanism are sample collection and manipulation in free-fall and in-situ analysis of cohesive forces in regolith at small bodies, such as asteroids or comets. Electrostatic finite element analysis was performed on various electroadhesion pad designs …

Numerical Study Of Synthetic-Jet Actuation Effect On Airfoil Trailing Edge Noise, Marco Sansone

Doctoral Dissertations and Master's Theses

The current study conducts numerical simulations to assess the possibility of employing Synthetic Jet Actuators (SJAs) as active noise control devices for reduction of airfoil acoustic radiation. High-accuracy numerical efforts employ a sixth-order accurate Navier-Strokes solver implementing a low-pass filtering of poorly resolved high-frequency solution content to retain numerical accuracy and stability over the range of transitional flow regimes. In the adopted numerical procedure, the actuator is modeled without its resonator cavity through imposing a simple fluctuating-velocity boundary condition at the bottom orifice of the actuator. The orifice cavity with the properly defined boundary condition is embedded into the airfoil …

The Three-Dimensional Turbulent Boundary Layer On A Rotating Disk, Daniel Digre

Doctoral Dissertations and Master's Theses

Three-dimensional turbulent boundary layers (3DTBL) are seen quite commonly in nature as well as in the engineering applications. Despite this, very few high Reynolds number studies have been carried out on these boundary layers, particularly focusing on eddy structure, eddy scales and their interactions. The current study focused on developing, characterizing and evaluating an experimental framework to study high Reynolds number #3DTBL on a rotating disk with the long-term goal of carrying out high-fidelity measurements. The rotating disk flow is characterized by weak centrifugal pumping which sets up the cross flow that leads to turbulence. The tangential and radial velocities …

Computation Of Hypersonic Flows With Lateral Jets Using K-Ω Turbulence Model, Spatika Dasharati Iyengar

Doctoral Dissertations and Master's Theses

Thermal Protection systems (TPS) are used as shields in space vehicles which encounter high heat and temperatures at the reentry altitudes. Among them, the cooling techniques and the ablative coatings are most popular. However, they have their own weight limitations. In the recent decade, another classification of TPS called the Non-Ablative Thermal Protection systems (NaTPS) have gained significance. The spike-lateral jet method is an NaTPS concept proposed for drag and heat flux reduction in hypersonic nose cones. Numerical simulations are conducted to analyze the effectiveness of spike-lateral jet concept at re-entry altitudes. The spike attached to the hemispherical nose has …

Open Source Toolkit For Reentry Object Modeling, Christopher Lloyd Ostrom Ii

Master's Theses

Predicting the mass, position, and velocity of an object during its reentry are critical to satisfy NASA and ESA requirements. This thesis outlines a 3-D orbit and mass determination system for use on low earth orbit as applicable to general objects, of various material and size. The solution uses analytical models to calculate heat flux and aerodynamic drag, with some basic numerical models for simple orbit propagation and mass flow rate due to ablation. The system outlined in this thesis currently provides a framework for rough estimates of demise altitude and final mass, but also allows for many potential accuracy …

Divergent Plume Reduction Of A High-Efficiency Multistage Plasma Thruster, Christopher M. Barlog

Master's Theses

High Efficiency Multistage Plasma Thrusters (HEMPTs) are a relatively new form of electric propulsion that show promise for use on a variety of missions and have several advantages over their older EP competitors. One such advantage is their long predicted lifetime and minimal wall erosion due to a unique periodic permanent magnet system. A laboratory HEMPT was built and donated by JPL for testing at Cal Poly. Previous work was done to characterize the performance of this thruster and it was found to exhibit a large plume divergence, resulting in decreased thrust and specific impulse. This thesis explores the design …

Spacecraft Trajectory Optimization Suite (Stops): Optimization Of Multiple Gravity Assist Spacecraft Trajectories Using Modern Optimization Techniques, Timothy J. Fitzgerald

Master's Theses

In trajectory optimization, a common objective is to minimize propellant mass via multiple gravity assist maneuvers (MGAs). Some computer programs have been developed to analyze MGA trajectories. One of these programs, Parallel Global Multiobjective Optimization (PaGMO), uses an interesting technique known as the Island Model Paradigm. This work provides the community with a MATLAB optimizer, STOpS, that utilizes this same Island Model Paradigm with five different optimization algorithms. STOpS allows optimization of a weighted combination of many parameters. This work contains a study on optimization algorithm performance and how each algorithm is affected by its available settings.

STOpS successfully found …

Inductive Monitoring Systems: A Cubesat Ground-Based Prototype, Michelle Haddock

Master's Theses

Inductive Monitoring Systems (IMS) are the newest form of health monitoring available to the aerospace industry. IMS is a program that builds a knowledge base of nominal state vectors from a nominal data set using data mining techniques. The nominal knowledge base is then used to monitor new data vectors for off-nominal conditions within the system. IMS is designed to replace the current health monitoring process, referred to as model-based reasoning, by automating the process of classifying healthy states and anomaly detection. An IMS prototype was designed and implemented in MATLAB. A verification analysis then determined if the IMS program …

Lightweight Deployment Mechanism Of Solar Arrays For Use In Cubesats, John Wood Ellis

Undergraduate Honors Capstone Projects

Cube satellites, also referred to as CubeSats, were developed in the late twentieth century, and have since served as a cost-effective method of gathering out-of-this-world data. The development of these small-scale satellites have helped universities and small companies worldwide to perform important experiments, as well as gather critical data in order to provide for further space exploration. Cube satellites are designed to be self-sustaining, by using solar cells to capture impinging thermal energy and convert it to power to be consumed by the electronics housed within the satellite itself. In order to function properly, these cells are extended in an …

Software-And Hardware-In-The-Loop Verification Of Flight Dynamics Model And Flight Control Simulation Of A Fixed-Wing Unmanned Aerial Vehicle, Calvin Coopmans, Michal Podhradsk, Nathan V. Hoffer

Mechanical and Aerospace Engineering Faculty Publications

Unmanned aerial system (UAS) use is ever-increasing. In this paper, it is shown that even with low-cost hardware and open-source software, simple numerical testing practices (software- and hardware-in-the-loop) can prove the accuracy and usefulness of an aeronautical flight model, as well as provide valuable pre-flight testing of many situations typically only encountered in flight: high winds, hardware failure, etc. Software and hardware simulation results are compared with actual flight testing results to show that these modeling and testing techniques are accurate and provide a useful testing platform for a small unmanned aerial vehicle. Source code used in simulation is open …

Volatile Condensible Material Deposition In Leo Simulated Environment, Jinya Pu

Department of Electrical and Computer Engineering: Dissertations, Theses, and Student Research

Room Temperature Vulcanized (RTV) silicone and compounds are widely used in outer-space for bonding or potting spacecraft components. In geosynchronous equatorial orbit (GEO), the silicone may outgas species which can condense on optically sensitive surfaces and degrade their performance, therefore shortening the lifetime of spacecraft. In low-earth-orbit (LEO), the silicone rubber is subject to an energetic and corrosive environment. Atomic oxygen (AO) and ultraviolet radiation can cause abrasion and degradation of the silicone rubber, cause changes in existing condensed VCM films and affect the properties of VCM films condensing in this atmosphere. Experiments were performed to simulate GEO conditions. In …

Evaluation Of Non-Volatile Particulate Matter Emission Characteristics Of An Aircraft Auxiliary Power Unit With Varying Alternative Jet Fuel Blend Ratios, Prem Lobo, Simon Christie, Bhupendra Khandelwal, Simon G. Blakey, David W. Raper

Mechanical and Aerospace Engineering Faculty Research & Creative Works

The aviation industry is increasingly focused on the development of sustainable alternative fuels to augment and diversify fuel supplies while simultaneously reducing its environmental impact. The impact of airport operations on local air quality and aviation-related greenhouse gas emissions on a life cycle basis have been shown to be reduced with the use of alternative fuels. However, the evaluation of incremental variations in fuel composition of a single alternative fuel on the production of non-volatile particulate matter (nvPM) emissions has not been explored. This is critical to understanding the emission profile for aircraft engines burning alternative fuels and the impact …

Wideband Fluorescence-Based Thermometry By Neural Network Recognition: Photothermal Application With 10 Ns Time Resolution, Liwang Liu, Kuo Zhong, Troy Munro, Salvador Alvarado, Renaud Cote, Sebastiaan Creten, Eduard Fron, Heng Ban, Mark Van Der Auweraer, N. B. Roozen, Osamu Matsuda, Christ Glorieux

Mechanical and Aerospace Engineering Faculty Publications

Neural network recognition of features of the fluorescence spectrum of a thermosensitive probe is exploited in order to achieve fluorescence-based thermometry with an accuracy of 200 mK with 100 MHz bandwidth, and with high robustness against fluctuations of the probe laser intensity used. The concept is implemented on a rhodamine B dyed mixture of copper chloride and glycerol, and the temperature dependent fluorescence is investigated in the temperature range between 234 K and 311 K. The spatial dependence of the calibrated amplitude and phase of photothermally induced temperature oscillations along the axis of the excitation laser are determined at different …

Sub-Orbital Spaceflight – An Addition To Our Multi-Modal Transportation System, Scott Haeffelin

Space Traffic Management Conference

The number of commercial spaceflights will be increasing by orders of magnitude over the next several decades. The current volume of space traffic can be managed on a case-by-case basis and there is little impact to the National Airspace System (NAS). This will change as more spaceports become operational, commercial sub-orbital flight companies begin serving their customers and as the cost of these flights begin to decrease. Current regulatory paths seek to allow the flexibility in the regulations for this industry to flourish while also maintaining a high standard of safety. There are, however, many nearsighted and old fashioned assumptions …

Space Data Integrator (Sdi) And Space Program Integrated Data And Estimated Risk (Spider): Proof-Of-Concept Software Solution For Integrating Launch And Reentry Vehicles Into The National Airspace System (Nas), Devin D. Dickens

Space Traffic Management Conference

The Space Data Integrator (SDI) Project is the initial step to satisfy the Federal Aviation Administration (FAA) strategic initiative to integrate commercial space launch and reentry vehicles into the National Airspace System. The project addresses the needs for greater situational awareness and monitoring, and increased response capability during non-nominal and catastrophic incidents during space operations.

The initial phase of this project leverages current FAA systems, and provide an initial demonstration of capability that will provide for state data from a commercial reentry vehicle to be ingested into a the FAA Traffic Flow Management System, and displayed on Traffic Situation Displays. …

Lunar Icecube: Nextstep Lunar Cubesat Mission And Instrument Concept, Robert J. Twiggs

Robert "Bob" Twiggs STEM Education Collection

A PowerPoint presentation created by Professor Bob Twiggs associates titled "Lunar IceCube: NEXTSTEP Lunar Cubesat Mission and Instrument Concept" from November 12, 2015.

Ehawk: Uav - Remote Launch Of Unmanned Aerial Vehicles Kite Based System, Matthew R. Rossett

Theses and Dissertations

Unmanned aerial vehicles, also known as UAVs or drones, are becoming favorable assets in multiple fields. Along with this new technology comes new improvements, including the EHAWK: UAV system, a proposed system to increase the range of UAVs by providing an alternate method for launching. The EHAWK: UAV is a kite based system for launching UAVs. The system uses a kite which acts as a sky anchor or fixed point in the sky. A tether is attached from the kite to the ground. A shuttle device then attached to the tether line. That shuttle carries the UAV up the line …

Materials For Programmed, Functional Transformation In Transient Electronic Systems, Suk Won Hwang, Seung Kyun Kang, Xian Huang, Mark A. Brenckle, Fiorenzo G. Omenetto

Mechanical and Aerospace Engineering Faculty Research & Creative Works

(Graph Presented). Materials and device designs are presented for electronic systems that undergo functional transformation by a controlled time sequence in the dissolution of active materials and/or encapsulation layers. Demonstration examples include various biocompatible, multifunctional systems with autonomous behavior defined by materials selection and layout.

A Study Of Ion And Electron Responses To A Dc Electric Field In A Hydrocarbon Flame, Stewart Jacobs

Von Braun Symposium Student Posters

No abstract provided.

Effect Of Electrode Geometry And Location On Electrically-Modified Flames, Paulo R. Salvador

Von Braun Symposium Student Posters

No abstract provided.

Characterization Of Pressure And Gps Altitude Measurement Techniques To 60,000 Ft., Trey Mcferrin

Von Braun Symposium Student Posters

No abstract provided.