Virginia Space Grant Consortium
Student Research Conference - April 16, 2007
Hosted by The College of William and Mary, Williamsburg, Virginia

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.