Virginia Space Grant Consortium
Student Research Conference – April 18, 2011
Omni Hotel, Newport News, Virginia

Graduate Research Fellows
Oral Presentations – Ball Room Ds
? 

Applied Science

A CAPACITANCE-BASED WHISKER-LIKE FLUID MOTION SENSOR
Jonathan Stocking, University of Virginia

The ability to navigate a fluid environment using only hydrodynamic information without visual or acoustic cues represents a technical challenge with broad utility for numerous commercial, military, and scientific purposes. Here we report the successful design, numerical modeling, fabrication, and experimental characterization of a novel, capacitance-based whisker-like artificial sensor for measuring fluid motion speed and direction.  Inspired by seal vibrissae, our design features a rigid artificial whisker mounted on a novel cone-in-cone parallel-plate capacitor base, separated into four distinct quadrants, and covered by a polydimethylsiloxane (PDMS) membrane.  The PDMS membrane creates the necessary damping and restoring forces, and the base divisions enable us to discriminate fluid direction. Numerical modeling of the system predicted capacitive output signals within a 1 pF range for flows ranging from 0 – 1.0 m/s. Experimental testing, however, using a custom-built force rig successfully demonstrated the sensor’s ability to produce a reliable signal with a 3 pF range for the same flows. The testing showed the sensor’s ability to discriminate flow-induced forces for both steady and oscillatory conditions with millinewton-level precision, and signal output from each of the four quadrants allowed us to extrapolate flow direction as well. Finally, the sensor was subjected to the same range of steady flows in our laboratory’s water tunnel and produced nearly identical capacitance changes as a function of flow speed compared to the force rig testing.

 

A BIO-INSPIRED SENSOR FOR FLUID MOTION DETECTION
William Eberhardt, University of Virginia

Biological hair fluid motion sensors can be found in a variety of animals such as arachnids, insects, crustaceans, fish, and mammals.  These sensors display a wide range of geometrical sizes and dynamical characteristics affecting their sensitivity depending on their purpose.  This paper examines a novel capacitance based sensor designed to detect fluid motion.  The sensor was experimentally subjected to a variety of input signals to develop a theoretical model of the sensor response. 

 

HYDRODYNAMIC CHARACTERIZATION OF AN AERTERIAL FLOW BIOREACTOR
Elizabeth Voigt, Virginia Tech

In vitro arterial flow bioreactor systems have been used in tissue engineering as models to investigate the response of endothelial cells to shear.  However, the degree to which such models can reproduce physiological flow has not been quantified. Furthermore, previous works have assumed a Poiseuille flow profile for the calculation of wall shear stresses (WSS) experienced by the endothelial layer.  To test the reliability of these systems and the accuracy of the Poiseuille assumption, a typical bioreactor used for tissue engineering was seeded with a layer of human microvascular endothelial cells on the lumen of the vessel section and integrated with a flow loop to generate pulsatile flow.  A particle image velocimetry (PIV) system was used to experimentally measure the flow within the bioreactor vessel.  The instantaneous and time-averaged WSS and oscillatory shear index were compared for different flow conditions and used to assess the system for study of the hydrodynamic response of biological tissues.  It was determined that the flow present in such a system is not an accurate reproduction of physiological flow. In light of these findings, conclusions about cellular response to hemodynamic parameters that were drawn from studies using such bioreactor flow systems should be reexamined.

 

EXECUTION TRACE ANALYSIS FOR THE SOFTWARE DEVELOPMENT OF SAFETY-CRITICAL SYSTEMS
Judith Providence, College of William & Mary

High quality software is an important part of mission critical systems.  In order to attain high quality software and detect potential errors, the software must go through a rigorous testing process. Our goal is to automatically relate test failures based on the similarity of their execution traces. Our research involves determining the similarity of execution traces based on appropriate measures.   Our approach shows promising results with real data.
 

BEYOND THE BACHELORS DEGREE:  INCREASING DOMESTIC STUDENT PARTICIPATION IN ENGINEERING GRADUATE
PROGRAMS

Erin Crede, Virginia Tech

If the United States is to remain a globally recognized source of technological and scientific development, it must continue to recruit and retain domestic students into engineering master’s and doctoral programs. Although enrollment of domestic students in graduate science and engineering programs rose by 5.9% in 2007-2008, it is still approximately half of the growth of international student enrollment (11.0%). The focus of this study is to develop a more complete understanding of the factors that contribute to students’ decision processes with respect to pursuing a graduate degree in engineering. In this paper, we present a brief overview of the instrument development along with the results from the survey, which examined how undergraduate engineering students viewed attending graduate school in engineering. Data were collected via an online survey instrument during the fall of 2010 at four universities across the United States, resulting in more than 1,000 respondents. Results of the quantitative analysis indicate that the presence of role models and students’ perceptions of their chance of success and level of knowledge about several aspects of graduate school contribute to the decision to enroll.  These results are discussed using a Social Cognitive Career Theory (SCCT) framework focusing on student self efficacy, and how they perceive graduate school’s alignment to their interests and future goals. The results of this study will help engineering faculty and administrators gain a better understanding of the issues surrounding the graduate school decision process, which will improve recruitment of potential graduate students and alleviate potential misconceptions regarding graduate engineering education.

 

UNIQUE IDENTIFICATION OF RADIO FREQUENCY IDENTIFICATION (RFID) TAGS
Corey Miller, College of William and Mary

Radio Frequency Identification (RFID) tags are used in credit cards and passports for automatic identity recognition and expense transfers as well as throughout the supply chain to track inventory.  The unauthorized electronic reproduction of these RFID signals is easily performed despite the use of developed encryption methods and can lead to critical security breaches and lost inventory.  A method for determining spoofed RFID tags is presented based on fingerprinting unintentional modulations in the electromagnetic signal of RF emitters.  Improvements to developed supervised pattern classification techniques are presented, utilizing the Dynamic Wavelet Fingerprint (DWFP) technique for feature extraction.

 

COGNITIVE RADIO APPLICATIONS IN WIRELESS MESH NETWORKS
Jonathan Backens – Old Dominion University

As the demand for flexible, self-organizing, large-scale wireless communication systems increases, there remain significant challenges to achieve optimal network performance. Multihop wireless mesh networks are currently being used to meet this demand. However, with variable number of nodes and diverse network densities, multihop wireless mesh networks are traditionally plagued by low overall network capacity and poor internode fairness. Therefore, we present the decentralized Traffic Aware Iterative Water (TAIW) filling power allocation algorithm.  TAIW applies theoretical techniques from non-cooperative game theory combined with the capabilities found in cognitive radio devices to develop a solution that balances overall network capacity, node fairness and power consumption. Through extensive simulations we show the TAIW can reduce congestion, increase internode fairness and reduce power consumption.
 

DIGITAL BASEBAND PREDISTORTION FOR TDRSS
Jakob Harmon, University of Virginia

Power amplifiers, an integral component to most wireless communication systems, are inherently nonlinear devices that introduce out-of-band spectral regrowth and constellation degradation to the amplifier output. One solution is to operate in a highly backed-off state to achieve quasi-linear performance. Operating in this region requires a higher-saturated power rating for a given output power and reduces DC-to-RF efficiency. A more effective solution is to apply digital predistortion which pre-compensates for the harmful nonlinear effects. Compensation can be done at the waveform level or operate at the symbol rate, known as data predistortion.  In this work, we study data predistortion for commonly adopted higher-order modulations, and study performance as a function of amplifier drive level relative to saturation, and as a function of the predistorter's memory span.  A math model for a nonlinear satellite with transponder filtering is employed.
 

MODELING BILAYER SYSTEMS AND ELECTRICAL NETWORKS
M. Austin Creasy, Virginia Tech

Bilayers are synthetically made cell membranes that are used to study cell membrane properties and make functional devices that incorporate inherent properties of the cell membranes.  Lipids and proteins are two of the main components of a cell membrane.  Lipids provide the structure of the membrane in the form of two leaflets, or layers, that are held together by the amphiphilic interaction between the lipids and water.  Proteins are made from a combination of amino acids and the properties of these proteins are dependent on the amino acid sequence.  Some proteins are antibiotics and can easily self-insert into the membrane of a cell or into a synthetically formed bilayer.  The peptide alamethicin is one such antibiotic that easily inserts into a bilayer and changes the conductance properties of the bilayer.   Analytical models of the conductance change with respect to the potential and other variables across the bilayer follow the nonlinear conductance changes seen with the incorporation of the peptide in a bilayer.  The individual channels formed by the peptide have been studied and the peptide has several discrete conductance levels.  These discrete levels have been shown to be dependent on the potential across the bilayer and several other variables including the lipid variety.  The conductance level for a single channel can change with time in a probabilistic fashion.  This paper will model these discrete conductance levels of the peptide alamethicin and the model of the single channel conductance will be used to model the cumulative effect of multiple channels within a bilayer.

 

TEST PROGRAM TO ISOLATE TEST FACILITY EFFECTS ON PERFORMANCE OF A DUAL-MODE SCRAMJET
Michael Smayda, University of Virginia

A low cost method for reducing the dispersion in the trajectory of an unguided, spin-stabilized, sounding rocket is developed and presented.  The method is particularly suited to scramjet flight experimentation because the approach increases the likelihood of meeting Mach number and dynamic pressure objectives.  The paper discusses the design and model of the scramjet payload, two-stage launch vehicle, and nominal trajectory as well as a Monte Carlo analysis to quantify the likelihood of a successful scramjet test.  Using the results of this analysis, a method is presented for reducing the dispersion in freestream conditions during the scramjet test window.  The dispersion reduction is accomplished by modifying the time delay between the burnout of the first stage booster and the ignition of the second stage based on the vehicle state measured during the interstage coast.  This method increases the likelihood of a successful test from 71% to 99% without adversely affecting range safety.   Since the design and implementation of a vehicle guided control system is not required, this method is relatively inexpensive, making its use highly desirable for low cost scramjet flight experimentation.

 

PERFORMING IMPACT ANALYSIS USING THE RELATION TOPIC BASED COUPLING
Malcolm Gethers, College of William and Mary

The proposed research defines a novel technique which applies an advanced Information Retrieval (IR) method to leverage textual information embedded in software artifacts in order to capture coupling between classes. More specifically, here we propose the use of new emerging IR techniques based on topic modeling, namely Relational Topic Model (RTM), to define a coupling metric useful for impact analysis.

 

POPULATION DYNAMICS OF THE BACTERIAL COMMUNITY DURING TUNICATE DECOMPOSITION
Maryse Leandre, Hampton University

Consideration of the trophic interactions that link species requires study of the decomposition process to reveal different pathways for nutrient regeneration, elemental recycling, and microbial production in the water column. Presently there is scarce literature on tunicate decomposition due to the difficulties in identifying and quantifying zooplankton carcasses in the natural environment. Nevertheless, the presence and activity of Gammaproteobacteria, Alphaproteobacteria and Sphingo-Flavobacteria are being assessed during decomposition of the filter-feeding tunicate, Dolioletta gegenbauri. Gammaproteobacteria often increase in micro- and mesocosms, Alphaproteobacteria are more abundant in increased salinity, and Sphingo-Flavobacteria increase with levels of high molecular weight. Culture-independent techniques are powerful tools to analyze the shifting population dynamics of bacterial communities during degradation of benthic and pelagic tunicates. Combined, the data obtained from these bacterial decomposition studies can contribute insights into the nutrient pathways between filter-feeding zooplankton and microbial communities following tunicate and plankton blooms.

 

A ROLE FOR STUBLS IN CHOROMOSOME MAINTENANCE
Jason Westerbeck, College of William and Mary

The budding yeast proteins Slx5 and Slx8 constitute the two subunits of a SUMO-targeted Ubiquitin Ligase (STUbL). Cells deficient in Slx5 and Slx8 exhibit gross chromosomal defects and extreme sensitivity to UV induced DNA damage. In vitro, the Slx5/Slx8 STUbL complex has been shown to target specific proteins for ubiquitylation in SUMO-dependent and SUMO-independent manners (Xie et al., 2007, Wang and Prelich, 2009, Xie et al., 2010). Slx5 is the targeting subunit of the Slx5/Slx8 complex while Slx8 performs the ubiquitin ligase function. Slx5 is a nuclear protein that forms distinct foci and interacts with double-stranded DNA breaks (Cook et al., 2009). However, little is known about the precise functional interactions of Slx5 in the nuclei of living cells. The goal of this research is to better characterize STUbL activity through a structure-function assay of individual Slx5 domains. Here we present our analysis of I) the domains involved in the subnuclear localization of Slx5; II) the domains within Slx5 required for interaction with its known binding partners; and III) a potential role for the Slx5/Slx8 STUbL in the regulation of protein sumoylation through the interaction with and putative regulation of an important SUMO pathway enzyme. Our research has the potential to further our understanding of the role STUbL activity plays in the control of SUMO and ubiquitin dynamics and chromosome maintenance.
 

 

Graduate Research Fellows
Oral Presentations – Amphitheater
Abstracts Grad2 2010-2011 

Planetary Science

DIKE EMPLACEMENT, ICE MELT AND HYDROTHERMAL PROCESSES ON MARS
Kate Craft, Virginia Tech

In analogy with hydrothermal processes on Earth’s seafloor, Martian hydrothermal systems may provide a mechanism for transporting water, chemicals, and energy to the surface. We model magmatic dike driven hydrothermal systems in which we consider changes to the surrounding permeability resulting from the emplacement of the dike and calculate water fluxes to the surface. When compared to formation requirements for the outflow channel Athabasca Valles, Mars, the fluxes are found inadequate to form the channel directly; although, if hydrothermal fluid collects in a subsurface reservoir and later releases episodically, the required volume of water can be supplied by 2 or more dikes emplaced into crust with a dike-induced permeability of ~10-10 m2. A layer of ice overlying the system could also melt through and contribute to the hydrothermal fluid flow, however ice melt volumes calculated are too low to contribute significantly for dike sizes considered. Further work through Summer 2011 will investigate the effect of internally pressurizing the dike and the resulting changes in stress field and permeability in order to provide an even greater understanding of the effect of dike emplacement on hydrothermal processes and surface morphology formation.

 

PLASMA VARIATIONS IN SATURN’S INNER MAGNETOSPHERE FROM THE MAIN RINGS TO ENCELADUS
Meredith Elrod, University of Virginia

With the discovery of an oxygen atmosphere over Saturn’s main rings by Cassini (Tokar et al., 2005; Johnson et al. 2006), as well a strong, but variable source from the plumes emanating from Saturn’s moon Enceladus (Porco et al., 2005; Smith et al., 2010) our picture of the physics of Saturn’s inner magnetosphere has changed dramatically.  The region of Saturn’s magnetosphere that lies inside the orbit of Enceladus and outside the edge of the main rings has oxygen scattered from the rings and water group ions from the Enceladus plumes, it is a region having high background, unique, but not well understood.  The purpose of this paper is to examine data from several passes from 2004 to 2010 from the edge of the main ring to inside the orbit of Enceladus and determine the interaction between the ring atmosphere and the Enceladus plumes.  Due to the high background of this region, the number of orbits that can be used with good pointing into the plasma is highly reduced to 7 passes, Saturn Orbit Insertion (SOI), one from 2005, 2 from 2007 and 3 from 2010.  Preliminary analysis indicates a large variation in ion density and temperature between SOI and 2010. 

 

Applied Physics

DEVELOPMENT OF NOVEL MAGNETO-PLASMONIC SENSORS OF INTEREST IN SPACE APPLICATIONS
Jonathan Skuza, College of William and Mary

Technological advances in sensor designs (e.g. increased sensitivity) may be achieved by combining plasmonic and magneto-optical materials, thus leading to magneto-plasmonic systems. Noble metal-ferromagnetic systems, such as Au/Co/Au trilayers and Au/FePd bilayers, are candidates for magneto-plasmonic systems, where surface plasmon polaritons (SPPs) may be modulated by externally applied magnetic fields. Optimization of these layered systems has been investigated leading to a large relative variation in the transverse magneto-optical Kerr effect (TMOKE) signal of 320% in the Au/Co/Au trilayers. Correlations between the structural and magnetic properties in Au/FePd bilayers have been understood using an analytical energy model, such that these properties may be tailored for sensing applications.

 

DESIGN OF A MINIATURE LIDAR SYSTEM FOR ROVER APPLICATIONS
Benjamin Robinson, Old Dominion University

Public awareness of harmful human environmental effects such as global warming has increased greatly in recent years and researchers have increased their efforts in gaining more knowledge about the Earth’s atmosphere. Natural and man-made processes pose threats to the environment and human life, so knowledge of all atmospheric processes is necessary. Ozone and aerosols are important factors in many atmospheric processes and active remote sensing techniques provide a way to analyze their quantity and distribution.

A compact ground-based lidar system for a robotic platform meant for atmospheric aerosol measurements was designed, tested, and evaluated. The system will eventually be deployed for ozone and aerosol measurements in Mars and lunar missions to improve our knowledge and understanding of atmospheres on Mars and the Moon. Atmospheric testing was performed to test the operability of the receiver system to acquire the lidar return signal from clouds and aerosols.

 

EXPERIMENTAL VALIDATION OF REDUCED CHEMICAL KINETIC MODELS FOR SCRAMJET PROPULSION
Brendyn Sarnarcki, University of Virginia

Fundamental flame characteristics derived from counterflow flames are routinely used in chemical kinetic model optimization and validation.  This paper reports an experimental investigation aimed at characterizing the extinction conditions of several thermally “cracked” liquid hydrocarbon species including methane-air, ethylene-air, propylene-air, and n-butane-air flames and identifying the sources of uncertainties associated with such characterizations.  In the experiments, convergent nozzles with exit diameters of 7.95mm were used to inject non-premixed fuel and air to establish a planar flame in the counterflow mixing region.  Velocity profiles and extinction data at various separation distances were measured using Laser Doppler Velocimetry (LV) or two-dimensional particle image velocimetry (PIV).  The slope of axial velocity in the axial and radial directions at the air outlet boundary was found to increase with decreasing separation distance.  The local extinction strain rate was found to be invariant to changes in separation distance within the uncertainty of experimental data.  Making use of the experimentally measured flow field boundary conditions, extinction results were compared to quasi one-dimensional computations using a recently optimized C1-C4 kinetic model.

 

WHISPERING GALLERY MODE RESONATORS FOR QUANTUM OPTICS AND INFORMATION EXPERIMENTS
Matthew Simons, College of William and Mary

We are developing high quality factor whispering-gallery mode resonator (WGMR) disks for use in quantum information experiments.  Our polished lithium niobate disks achieved quality factors of Q > 107. We observed the generation of λ = 532 nm through Type-I, noncritically phase matched second harmonic generation in our whispering-gallery mode resonator disk. Unexpectedly, we observed this second harmonic generation far from phase matching conditions (a difference of more than 100 oC). The non-phase matched second harmonic was significant enough to produce stimulated Raman scattering at λ = 545 nm, 559 nm, 573 nm, and 587 nm.

 

VERIFICATION STUDIES OF A THREE DIMENSIONAL GRNTRN CODE IN BOTH LABORATORY AND SPACE
Candice Rockell Gerstner, Old Dominion University

In the future, astronauts will be sent into space for longer durations of time compared to previous missions.  The increased risk of exposure to ionizing radiation, such as Galactic Cosmic Rays and Solar Particle Events, is of great concern. Consequently, steps must be taken to ensure astronaut safety by providing adequate shielding.  In order to better determine and verify shielding requirements, an accurate and efficient radiation transport code based on a fully three dimensional radiation transport model using the Green's function technique has been developed (GRNTRN).  This paper will outline the approximations used in the formulation of the three dimensional GRNTRN code and also discuss verification studies in both a laboratory and a space environment.

 

EXPERIMENTAL INVESTIGATION OF AIRFOIL THERMOSYPHONS FOR THERMAL MANAGEMENT OF NEXT GENERATION AIRCRAFT
Christina Johnson, University of Virginia

Airfoil-shaped thermosyphons were designed, manufactured, and tested to investigate their performance (rate of heat transfer) for cooling applications. One thermosyphon had a cylindrical cavity and the other had a slot-shaped cavity. The thermosyphon material was copper, and the working fluid was deionized water. The fill volumes (as a percentage of the entire cavity volume) tested were 0%, 5%, and 20%. The condenser section was air-cooled in a wind tunnel with wind speeds of 100 mph and subjected to a range of evaporator temperatures. The rate of heat transfer with no working fluid was 156.5 W at the evaporator temperature design point of 315 F. The rate of heat transfer at the design point was the highest at the 5% fill volume at approximately 323.1 W. The highest thermosyphon performance was at 5% fill volume for all evaporator temperatures. As fluid is added to the thermosyphon, the surface temperature rises and the temperature distribution becomes more isothermal, explaining the observed increase in performance.

 

DEVELOPMENT OF CAPABILITY OF WATER FLUX MEASUREMENT IN A SCRAMJET COMBUSTER USING TUNABLE DIODE LASER ABSORPTION TOMOGRAPHY AND STEROSCOPIC PIV
Kristin Busa, University of Virginia

Tunable Diode Laser Absorption Tomography (TDLAT) is a non-intrusive measurement technique for determining two-dimensional spatially resolved distributions of temperature and species concentration in high enthalpy flows.  TDLAT combines infrared laser absorption spectroscopy with tomographic image reconstruction.  The TDLAT technique has been implemented at the University of Virginia's Aerospace Research Laboratory supersonic combustion tunnel.  Spatially resolved temperature and water vapor concentration measurements at the exit of the supersonic combustion tunnel have been obtained using the TDLAT technique. The tomographic reconstructions at the exit plane are presented. Water vapor concentration measurements from TDLAT are combined with velocity measurements obtained by Stereoscopic PIV to provide direct measurement of water vapor flux at the exit of the supersonic combustion tunnel. Comparison of this value to the known water vapor injected provides a demonstration of the capability of the TDLAT/SPIV technique. Such a measurement of water flux with combustion will enable combustion efficiency to be evaluated. A measurement of a high temperature non-reacting case for a water vitiation level of 12% is presented.

 

QWEAK:  A SEARCH FOR NEW PHYSICS
John Leckey, College of William and Mary

The standard model of particle physics has been quite successful in the description of the electromagnetic, weak nuclear, and strong nuclear sectors of particle physics; however, it is known to be insufficient to completely describe nature.  Qweak is a running experiment at Thomas Jefferson National Accelerator Facility (JLAB) that uses high precision electron proton scattering to measure the weak nuclear charge of the proton.  This measurement of the weak coupling will allow the effective probing of the 1.5 to 2.5 TeV region that is believed to contain new physics.  To ensure accuracy, there are tracking devices throughout the full apparatus to measure the positions and trajectories of the scattered electrons.  The tracking device that will be further detailed in this report is known as a vertical drift chamber (VDC).  All 5 of the VDCs have been built, tested, installed, and are currently in use at JLAB.

 

DIRECT MONTE CARLO SIMULATIONS OF THERMALLY DRIVEN ATMOSPHERIC ESCAPE:  APPLICATIONS TO TITAN AND PLUTO
Orenthal Tucker, University of Virginia

Recent models of the atmospheres of both Pluto and Titan estimate large thermal escape rates of the principal atmospheric species in comparison to their respective Jeans theoretical rates. However, these continuum models were applied region of the atmosphere that transitions from being collisional to collisionless. In particular, the ‘slow hydrodynamic escape’ model requires assumptions about the thermal conduction and temperature in the exosphere which favors large escape rates. The difficulties with the slow hydrodynamic approach are related to the model assumptions concerning the atmospheric structure at infinity. Here a kinetic model is used to account for non-equilibrium collisions in the exosphere, and it is found that thermal escape of N2, CH4 and H2 from Titan and N2 from Pluto should occur similar to Jeans rate. In addition a hybrid fluid/DSMC approach has been developed to obtain consistent results for the escape rate and macroscopic properties of Pluto’s atmosphere between a continuum and kinetic approach.  A summary on the DSMC model is provided with current results for escape from Titan and Pluto.
 

SIMULATION OF ORGANIC/INORGANIC TANDEM SOLAR CELLS
Patrick Boland, Old Dominion University

Computer simulation of tandem organic/inorganic solar cells is a useful tool for exploring several expected device performance characteristics prior to expending resources to fabricate real devices. The modeling of such factors as component layer thicknesses, carrier mobilities, and recombination efficiencies allows the calculation of theoretical values for short circuit current density (JSC), open circuit voltage (VOC), fill factor (FF), and power conversion efficiency (PCE). Additional parameters critical to the accurate prediction of solar cell behavior include the bandgap of the electron-donating polymer and choice of electron-acceptor material. Incorporating the aforementioned factors into our computer model, we endeavored to optimize each using optical and electrical simulation algorithms. Our results show that much-improved power conversion efficiencies are obtainable if appropriate fabrication materials are selected and assembled in the correct order. By doing so, it is possible to design high-efficiency cells with performances that exceed those of current state-of-the-art tandem organic photovoltaics.

 

Graduate Research Fellows
Oral Presentations – James River Room B
Abstracts Grad3 2010-2011 

Aerospace

AEROELASTIC SCALED FLIGHT TEST OF A JOINED WING SENSORCRAFT CONFIGURATION
Tyler Aarons, Virginia Tech

The design, construction and flight testing of a 1/9th scale, aeroelastically scaled model of the Joined Wing SensorCraft is the subject of an ongoing international collaboration aimed at experimentally demonstrating the nonlinear aeroelastic response associated with the configuration.  To measure and characterize the desired response, the aircraft must exhibit equivalent aeroelastic properties while also being designed for flight worthiness.  Additionally, the aircraft must be instrumented to record the required structural response data.  Flight testing of the 1/9th scale Joined Wing SensorCraft will begin with a rigid prototype.  Current work at Virginia Tech includes instrumentation system design and testing, flight testing of reduced complexity models and flight test planning.  A parallel effort at Quaternion Engineering in Victoria, BC includes the structural design and fabrication of the test article as well as simulation of flight test maneuvers.  Final preparations are underway for the first flight test, scheduled to go wheels up in May 2011.
 

ONE DIMENSIONAL ANALYSIS PROGRAM FOR SCRAMJET AND RAMJET FLOWPATHS
Kathleen Tran, Virginia Tech

One dimensional modeling of dual mode scramjet and ramjet flowpaths is a useful tool for scramjet conceptual design and wind tunnel testing.   Modeling tools that enable detailed analysis of the flow physics were developed and implemented as part of a one-dimensional MATLAB-based model named VTMODEL.  VTMODEL divides ramjet or scramjet flow paths into four major components: inlet, isolator, combustor, and nozzle.  The inlet module provides two options for supersonic inlet calculations: MIL Spec 5007D and a kinetic energy correlation with the option of a total temperature term.  The isolator model calculates the pressure rise and the isolator shock train using two different methods.  The two models are a combined Fanno flow and oblique shock system, and a rectangular shock train correlation.  There are also two options for the combustor module: a non-equilibrium reduced-order hydrogen calculation using a mixing correlation.  The second option is an equilibrium hydrogen calculation with a “growing combustion sphere” combustion model which is adaptable to any fuel.  Both models calculate Mach number and thermodynamic flow properties using a 4th order Runge Kutta solver. The model can take into account heat transfer, change in specific heat ratio, change in enthalpy, and other thermodynamic properties.

 

INVESTIGATION OF INTERACTIONS OF REACTION CONTROL SYSTEM JETS WITH MSL AEROSHELL
Erin Reed, University of Virginia

The use of Reaction Control System jets becomes increasingly important as strides are made towards more accurate landings on missions to Mars.  This work focuses on increasing understanding through qualitative and quantitative experiments conducted on an MSL aeroshell model fitted with transverse and parallel jets.  Experiments were conducted using the Planar Laser Induced Iodine Fluorescence diagnostic technique for qualitative images.  The experiment was conducted at Mach 12 with the model set at a twenty degree angle of attack in the freestream, at different thrust coefficients ranging from 0 to 3.  It was found that the transverse jet affected the bow shock off the aeroshell and the parallel jet had little interaction.  Current work involves updating the setup to obtain quantitative planar velocity data.  The resulting data should yield greater understanding about the RCS jets and their interactions with the aeroshell and the freestream.  It is anticipated that this data will also serve to validate CFD code for use in prediction of heating and induced moments on the aeroshell at the critical shoulder.

 

AEROELASTIC ANALYSIS FOR NEAR-SPACE APPLICATIONS IN ULTRA-LARGE ASPECT RATIO WINGS
Lauren Butt, Virginia Tech

This research describes an aeroelastic modeling method for use within an optimization framework combining rigid and inflatable wing design. The inflatable portion of the wing is stowed within the rigid portion of the wing when not in use; this is done using a telescoping spar system. The aeroelastic analysis of the wing is critical in determining a feasible design using a multidisciplinary design optimization framework, and the approach must handle the discontinuities between sections of the wing. The natural modes are determined using the Rayleigh-Ritz method, while continuity between each section of the wing is handled using a penalty approach. The penalty parameters are determined and the method is verified using a comparison of the predictions from this method with known natural modes for simple examples.

 

AVIATION IN THE ALASKAN FRONTIER
Jennifer Camp, College of William and Mary

Flight is often cited as one of the most remarkable achievements of the 20th century.  Aviation has profoundly altered the interconnectedness of the world; changing the ways in which we think about distance, time, and space.  In North America, Alaska is one area in particular that has been significantly affected by aviation.  There are very few places in which aviation is so tightly integrated into society.  Alaska has more pilots and more aircraft per capita than any other place in the United States; but despite the importance of aviation within the state, little anthropological or archaeological research has been conducted on this topic.  By examining the cultural, social, and material aspects associated with flying, planes, and pilots in this distinct area of the world, this research creates a more complete understanding of aviation within the social history of the Alaskan frontier.

 

INVESTIGATIONS OF PERIPHERAL 4-JET SONIC AND SUPERSONIC PROPULSIVE DECELERATION JETS ON A MARS SCIENCE LABORATORY AEROSHELL
Joshua Codini, University of Virginia

With the launch of Mars Science Laboratory (MSL), scheduled for 2011, Viking technology developed in the 1970's is reaching its limits for entry, descent and landing (EDL) on Mars, necessitating research and development of other technologies for decelerating high mass Mars entry systems (HMMES), such as propulsive deceleration (PD) jets. In this paper planar laser-induced iodine fluorescence is utilized to obtain qualitative flow visualization images and quantitative PD jet mole fraction images of peripheral sonic and supersonic PD jet models in Mach 12 flow and compared to CFD computations. The models are 0.22% of the MSL frontal area, with Mach 1 and Mach 2.66 jets on the frontal aeroshell of the model, oriented normal to the hypersonic flow. The interactions of PD jets with a Mach 12 freestream flow are visualized with coefficients of thrust (CT) varying from 0.5 to 3.0 in increments of 0.5. It was found that as CT increases the shock stand-off distance increases for both sonic and supersonic cases, with the supersonic distance at a CT = 3.0 being 17% greater than the sonic distance. The jet penetration distance was measured to be 50% greater for the supersonic case at a CT = 3.0. PD jet fluid distribution was also found for sonic and supersonic configurations at a CT of 1.5. The PD jet fluid distribution show a lack of PD jet fluid between the peripheral jets, which indicates the preservation of the bow shock and possible preservation of drag.

 

SEARCHING FOR CHEMICAL EVIDENCE OF PLANET ENGULFMENT IN RAPIDLY ROTATING RED GIANT STARS
Joleen Miller-Carlberg, University of Virginia

Rapid rotation in red giant stars may signify a violent past if the unusually large angular momentum was gained through the engulfment of a planetary companion; we explore the feasibility of this spin-up mechanism both theoretically and observationally. By modeling the tidal interaction of known extrasolar planets and their host stars, we have found that many exoplanets will be engulfed during future stellar evolution and the orbital angular momentum of these accreted planets is often sufficient to cause   rapid rotation. Planets accreted during the red giant phase should leave behind a chemical signature in the form of unusual abundance patterns in the host red giant's atmosphere. Proposed signatures include the replenishment of both lithium and, to a lesser degree, 12C/13C (which are depleted in giant stars' atmospheres) and an enhancement of refractory elements (which are relatively more abundant in planets). We compiled a sample of both rapid and slow rotators to look for these chemical signatures and have found that the average Li abundance is enhanced in the rapid rotators compared to the slower rotators. We find no measurable 12C/13C enhancement; however, this is consistent with planet accretion at the level implied by the Li enhancement.

 

PROGRESS REPORT FOR SCRAMJET RESEARCH VSGC GRADUATE FELLOWSHIP PROGRAM
Christopher Rock, Virginia Tech

A flush-wall injector model and a strut injector model representative of state of the art scramjet engine combustion chambers were experimentally studied in a cold-flow (non-combusting) environment to determine their fuel-air mixing behavior under different operating conditions. The experiments were run at nominal freestream Mach numbers of 2 and 4, which simulates combustor conditions for nominal flight Mach numbers of 5 and 10. The experiments investigated the effects of injectant molecular weight and freestream Mach number on the fuel-air mixing process. The primary goals of this study were to use injector models that represent state of the art scramjet engine combustion chambers to provide validation data to support the development of turbulence model upgrades and to add to the sparse database of mixing results in such configurations. The main experimental results showed that higher molecular weight injectants had approximately the same amount of penetration in the far field as lower molecular weight injectants at the same jet-to-free-stream momentum flux ratio. Higher molecular weight injectants also demonstrated a mixing rate that was the same as or slower than lower molecular weight injectants depending on the flow conditions. A comparison of the experimental results for the two different injector models revealed that the flush-wall injector mixed significantly faster than the strut injector in all of the experimental cases.
 

MODEL VERIFICATION AND VALIDATION FOR MULTI-BODY DYNAMICS AND IMPACT TESTING
Scott Tedesco, Old Dominion University

Using MSC’s Adams software a multi-body dynamic model was created to represent a Six Degrees of Freedom (Six DOF) Machine, located at the Old Dominion University Dynamic Environment Simulation Laboratory (DES Lab).  This rigid body model will be verified and validated for single axis impact using two methods: a mathematical model of a multi-body dynamic system of rigid bodies, and experimental test data from the Six DOF Machine for various impact accelerations.  Due to the large number of unknowns in the physical Six DOF Machine, the design sensitivity of several parameters will be evaluated and optimized in order to maximize the model accuracy.  Once the Six DOF Machine model has been fully validated, any testing fixture may be input into the model and analyzed in the early design stage.

 

Astrophysics

EXOPLANETARY EXPLORATION AND CHARACTERIZATION WITH LMIRCAM AT THE LARGE BINOCULAR TELESCOPE
Jarron Leisenring, University of Virginia

Direct detection of extrasolar planets and their surrounding environments provides an excellent opportunity to study the dynamical evolution of extrasolar planetary systems.  With increased angular resolution and sensitivity, unprecedented details of these systems' architectures will be revealed.  Direct imaging of low-mass giant planets in wide-separation orbits complements existing indirect detection techniques and provides a more complete census of the diversity of planetary systems and their dynamical evolutions.  This project utilizes the Large Binocular Telescope Interferometer (LBTI) to directly image and characterize planetary systems around nearby solar-type stars.  LMIRcam, a 3-5 micron imager/spectrograph for the LBTI, will probe nearby stars for giant planets with wide orbital separations and acquire spectra of exoplanet atmospheres.  These observations will be performed in tandem with NOMIC, a NASA-funded 10-micron nulling camera co-located within the same cryost at the University of Arizona.  By themselves, LMIRcam observations provide significant insight into the formation and evolution of planetary systems, the diversity of extrasolar planets, and atmospheric model constraints.  By combining LMIRcam and NOMIC's capabilities, observations of these systems will provide revolutionary insights into the dynamics between extrasolar giant planet and their terrestrial companions, and represents a major step towards characterizing habitable planetary systems.
 

CHARACTERIZING MASS LOSS FROM TIDALLY-LOCKED EXOPLANETS
George Trammell, University of Virginia

Gas giant exoplanets orbiting very close to their host stars (i.e., the “hot Jupiters”) represent a unique opportunity to study planets in an extreme environment not found within our own Solar System.  Heating from the host star may create an extended upper atmosphere of gas observable through transmission or reflection spectroscopy, and drive an outflow through thermal pressure gradients leading to mass and angular momentum loss from the planet.  I will summarize what we are learning about mass loss from hot Jupiters through new magnetohydrodynamical modeling efforts, taking into account tidal forces from their host stars.  Our results suggest a fundamentally different interpretation for transit observations of hot Jupiters that have revealed surprisingly high neutral gas densities beyond the planet’s Roche Lobe.

 

ELECTRONICALLY EXCITED STATES OF INTERSTELLAR ANIONS
Ryan Fortenberry, Virginia Tech

In the search for carriers of the diffuse interstellar bands (DIBs), a nearly ubiquitous, as-of-yet unattributed interstellar absorption spectrum, new theories are being proffered to explain this astronomical phenomenon.  One of these is that rarely occurring excited states of anions may be responsible for some of these features.  Using state-of-the-art quantum chemical techniques we examine nearly twenty anions for their excited state properties. Using two known species as benchmarks, nine new molecules about which little is known are shown to possess dipole-bound excited states while three of these (CH2SiN-, SiCCN-, and CCSiN-) are predicted by our methods to possess both dipole-bound and potentially even valence-bound excited states, an incredibly rare circumstance.  These anions may yet hold significance for the chemistry of the interstellar medium and for the DIBs.

 

IMPACT OF THE COMPACT GROUP ENVIRONMENT ON GALAXY EVOLUTION
Lisa May Walker, University of Virginia

Compact groups of galaxies (CGs) are extremely dense groups of galaxies, where the galaxy separation is approximately the size of a galaxy. These groups provide a local analog to galaxy interaction in the early universe. The frequent and prolonged gravitational encounters in CGs affect the evolution of member galaxies in myriad ways. To probe this, we have compared the mid-infrared (MIR) properties of galaxies in CGs with several control samples. We find that the CG galaxies exhibit a "gap" in their MIR properties, and only galaxies in the Coma infall region have MIR properties that are statistically consistent with the CGs. We conclude that the unusual MIR color distribution of CG galaxies is a direct product of their environment, which is most similar to that of the Coma infall region. Both environments have high galaxy densities, but gas is still available for star formation. We speculate that this environment fosters accelerated evolution of galaxies from star-forming and neutral gas-rich to quiescent and neutral gas-poor, yielding a gap in MIR properties. To investigate this gap, we have compiled a sample of 49 compact groups, and find that an underrepresentation of galaxies in this gap region is persistant.



Aerospace Undergraduate Research Scholars Research Papers



A Low Density Parity Check (LDPC) Code Decoder in a Field Programmable Gate Array (FGPA)
Aaron Albin, University of Virginia

This project concerned the design of a Low Density Parity Check (LDPC) code decoder in a Field Programmable Gate Array (FGPA).  LDPC codes are a well known type of coding technique being used in a variety of high performance communication applications.  Specifically, the goal of this project was to create a decoder simulator to test the effectiveness of any particular type of LDPC code one would choose to construct.  The parity check matrix of an LDPC code is structured in a way so that can make good use of parallel processing, thereby dramatically increasing the throughput of the decoder.  The full design was supposed to have been completed in System Generator, but that software platform proved to be insufficient for this project.  Therefore, a program was written to generate the text of the hardware description language code necessary to implement any size code corresponding to any matrix desired.  As these designs were being tested in software simulation, the focus of this project shifted more towards understanding input and output constraints.  The remaining work for this project includes, assignment of appropriate input and output constraints, random number generator input design, redesign of the variable and check nodes without the use of System Generator, and simulation and debugging in hardware.  These remaining tasks should be completed during the summer of 2007.  After a small code is fully tested on a small board, a larger FGPA within a development board will be purchased so that larger codes can be tested.  The hardware decoder can be used to simulate different types of parity check matrices in a significantly smaller amount of time than it would take to do so in software.

The Gravitational Harassment of Our Dwarf Galactic Neighbors
Rachel Beaton, University of Virginia

The Local Group of galaxies contains some 40 galaxies, most of which fall into two morphological classes: dwarf Irregulars (dIrrs) and dwarf Spheroidals (dSphs). dSphs are preferentially located in the densest regions of the Local Group, where they are more likely to have experienced interactions with large galaxies. dIrrs, however, are located far from large galaxies, where they are less likely to have seen recent interactions, which have the potential to strip gas and inhibit future star formation. Furthermore, in optical observations, dIrrs are dominated by patches of young stars and regions of ongoing star formation, whereas dSphs are dominated by a smooth distribution of old stars with none having been observed with ongoing star formation, from this it is proposed that dIrrs are the "pre-harassed" versions of dSphs. In this study, we analyze the distribution of old stars in two Local Group dIrrs, Leo A and Sextans B. This is accomplished with a semblance of wide field, but resolution limited, ground based imaging and small area, but highly resolved, archival space based imaging from the Hubble Space Telescope. By combining the strengths of these two datasets, a population of old stars has been found beneath the patchy young populations, which is smoothly distributed much like those of dSph galaxies.

Optimal Electrodynamic Tether Phasing Maneuvers
Matthew Bitzer, Virginia Tech

This paper studies the minimum-time orbit phasing maneuver problem for a constant-current electrodynamic tether (EDT).  The EDT is assumed to be a point mass that is always in a plane perpendicular to the local magnetic field.  After deriving and non-dimensional the equations of motion, the only input parameters become current and the phase angle.  Solution examples, including initial Lagrange costates, time of flight, thrust plots, and thrust angle profiles, are given for a wide range of current magnitudes and phase angles.  The two dimensional cases presented use a non-tilted magnetic dipole model, and the solutions are compared to existing literature.  We are able to find similar trajectories to that of a constant thrust phasing maneuver, however, the time of flight is shorter.  Full three dimensional solutions, which use a titled magnetic dipole model, are also presented for various inclined orbits.

Materials Development For Mid-Infrared Solid-State Lasers
Monique Calhoun, Hampton University

The purpose of this research is to evaluate new materials as gain media for mid-infrared (MIR) solid-state lasers. MIR lasers are of significant current interest for several applications including laser remote sensing of bio-chemical agents, medical surgery, fundamental spectroscopy, and biophotonics. In this project, Cobalt (Co) doped ZnSe windows and CdTe/ CdMnTe crystals were investigated as MIR laser media. These materials were Co doped through a thermal process called diffusion doping. The optical properties of Co: ZnSe and Co: CdTe were investigated through transmission spectroscopy and emission spectroscopy. The obtained spectroscopic data of Co: ZnSe and Co: CdTe will be discussed for applications in MIR solid-state lasers.

Thermal Management For A Proposed Hypersonic Scramjet Flight Test
Elizabeth Croft, University of Virginia

The latest in hypersonic technology is the supersonic combustion ramjet, or scramjet. This air-breathing jet engine is capable of achieving speeds in excess of Mach 10 without the use of moving components or the aid of an onboard oxidizer. Researchers at the University of Virginia are currently testing a phase of scramjet operation known as mode-transition in their hypersonic wind tunnel. Wind tunnel testing, however, can only provide limited understanding, and in order to develop a truly reliable scramjet, the Hy-V project will conduct the first mode-transition flight test of a dual-mode hypersonic scramjet. A sounding rocket will be used to propel the scramjet to Mach 5 where the mixing of fuel and air for combustion is optimum and an altitude of 28 kilometers where the flow conditions simulated by the wind tunnel are matched. Heating of the payload during this flight is of great concern, since it is a goal of the project to recover the payload unharmed. The heat transferred to the exterior of the rocket as well as the combustion chamber’s interior have been calculated, opening the way for future finite element temperature analyses. For thermal management, ablative surfaces and heat sink options have also been researched.

Optimization of the Geometry of a Heat Sink
Matthew de Stadler, University of Virginia

Cellular materials have properties similar to conventional materials on the macroscopic level but possess several advantages at the microscopic level, including the ability to be manufactured down to a very small scale. With this ability, new geometric configurations for a heat sink are able to be considered. This paper details the results of a study to develop a geometry based optimization tool for heat sink design. With the principle of superposition, the analysis of a heat sink can be simplified by using a repeating cell. For the repeating cell, the following questions are posed: Given a certain percentage of the volume available for channels for fluid to pass through, where should one place the channels? What shape should they be? To answer these questions a theoretical approach was used with testing and analysis performed using
computational fluid dynamics software. Three unsuccessful schemes are presented, with explanations as to why they did not prove successful. Lessons learned from these attempts are applied to the ongoing development of an optimal heat sink for use in skin cooling of a hypersonic vehicle.

Implementation and Testing of a Freestream Seeding Apparatus For A Supersonic Combustion Wind Tunnel
Daniel J. Glanz, Jr., University of Virginia

Scramjet engines promise to allow efficient and inexpensive access to the hypersonic flight regime, but more complete data on internal flow properties is needed to improve computer models, and develop working prototypes. The supersonic combustion wind tunnel at the University of Virginia was specifically designed to simulate the combustion chamber of a scramjet operating at Mach 5. Currently the tunnel can only produce velocity data from the region where hydrogen fuel is injected. Data acquisition relies on imaging the movement of small particles embedded in the flow. The tunnel is equipped with an apparatus for seeding the hydrogen fuel, but not the air. Previous undergraduate researchers designed and built an apparatus to solve this problem by seeding the freestream. In the instant work, their device was installed, modified, and tested.

Initial testing showed that the design was basically functional, but the size of the particles produced was at least one order of magnitude larger than desired. The literature suggested that the simplest and most cost effective way to break up the particles was by including a layer of large beads through which the particles would move. Final testing showed the opposite effect, with mean particle size increasing. Intermittently agitating the main component of the seeder resulted in improved particle density, but even higher mean particle diameter.

Future improvements to the freestream seeding apparatus must include a more robust scheme to reduce particle size, such as a shearing nozzle. Permanently installing a mechanical agitator may help increase seeding density, and alleviate some particle clumping.

Hy-V Scramjet Inlet
Christina McLane, Virginia Tech

Hy-V is an undergraduate student-led scramjet engine test project. There are multiple teams at several Virginia universities working in collaboration on the project. One of the Virginia Tech teams is designing the flow path for the scramjet engine. Three different inlets for this engine have been designed for future testing. These include a two-dimensional four-shock ramp inlet, a two-dimensional three-shock conical inlet, and a three-dimensional stream-tube inlet. Wind tunnel testing is scheduled and will examine the qualities of the flow in these inlets. The results of the tests will determine which inlet is chosen for the flight test of the scramjet engine. 

Plasma Torch Power Control For Scramjet Application
Mark A. Peretich, Virginia Tech

Plasma torches have proven reliable methods of ignition and flame-holding for supersonic combustion applications. The Hy-V Scramjet Flight Experiment plans to use an 800W plasma torch for ignition of hydrogen fuel in a Mach 2 flow—a “first” in a freeflight scramjet experiment. Torch power will be controlled by a proportional feedback system monitoring feedstock pressure, fuel pressure, and a combustion-chamber infrared flame sensor. Original designs are required for the hardware and control system of the plasma torch operating under these conditions. This paper will discuss the design and construction of a battery power source and controller to achieve and sustain supersonic combustion.

Scramjet Systems Integration for a Dual-mode Hypersonic Scramjet Flight Test
James Thompson, University of Virginia

The Hy-V project will conduct the first mode-transition flight test for a dual-mode hypersonic scramjet, which will occur at approximately 90,000 feet onboard a sounding rocket. At altitude, atmospheric conditions and inlet flow speed will match the flow conditions simulated in the UVA Aerospace Research Laboratory (ARL) hypersonic wind tunnel. Geometric similarity between the wind tunnel and flight-test flow path presents a unique opportunity to calibrate the two environments. This, however, requires a close agreement between the flight and ARL wind tunnel flow conditions, fuel injection systems, combustion environment, and exhaust pressure. This research presents strategies for transitioning the ARL hypersonic wind tunnel into the payload of a sounding rocket in a matter that optimizes the desires similarity. Space constraints in the scramjet’s flight-test configuration require an innovative approach to managing fuel storage, fuel mass flow rate, data acquisition, and exhaust. In addition, this research considers factors such as budgetary constraints and thermal management to optimize the implementation of pressure and temperature recording devices implanted in the flow path wall.