Aerospace Engineering Commons^™

A Variable Acceleration Calibration System, Thomas H. Johnson

Mechanical & Aerospace Engineering Theses & Dissertations

A variable acceleration calibration system that applies loads using gravitational and centripetal acceleration serves as an alternative, efficient and cost effective method for calibrating internal wind tunnel force balances. Two proof-of-concept variable acceleration calibration systems are designed, fabricated and tested. The NASA UT-36 force balance served as the test balance for the calibration experiments. The variable acceleration calibration systems are shown to be capable of performing three component calibration experiments with an approximate applied load error on the order of 1% of the full scale calibration loads. Sources of error are indentified using experimental design methods and a propagation of …

Acoustic Characterization Of The Nasa Langley 14 X 22 Ft Subsonic Wind Tunnel, James Thomas Crippen

Mechanical & Aerospace Engineering Theses & Dissertations

Aero-acoustic testing is used to identify and characterize acoustic sources of test articles within a flow field. Such testing requires high signal-to-background noise level ratios (5 - 10 dB) and an anechoic test chamber. The NASA Langley 14 x 22 ft Subsonic Wind Tunnel is evaluated with respect to operating noise levels and to architectural acoustic characteristics. Operating noise level measurements include power spectral densities, 1/3 octave plots, and overall sound pressure levels. Architectural acoustic measurements are centered around reverberation analysis. A lumped parameter model, based on a technique applied in architectural acoustics to study noise propagation between connected rooms, …

Boundary Layer Measurements Related To Wind Tunnel Testing Of Riblets, Emrah Cinar

Mechanical & Aerospace Engineering Theses & Dissertations

With fuel economy being a significant factor in today's world of aviation, aircraft manufacturers have been looking into ways to decrease drag to save fuel. Drag reduction using riblets on wing and fuselage surfaces is . an area that has been studied extensively for the last two decades. In preparation for a larger project which will use several methods to simulate this phenomena, small scale research had to be done to find ways to generate similar conditions on scaled models in a low speed wind tunnel and examine boundary layer behavior.

In this project, boundary layer measurement techniques, such as …

Spacecraft Demand Tasking And Skip Entry Responsive Maneuvers, Robert A. Bettinger

Theses and Dissertations

The purpose of this research was to parametrically investigate the viability of skip entry maneuvers as an alternative to vacuum-only maneuvers, and to identify whether skip entry maneuvers can extend spacecraft mission lifetime by limiting propellant expenditure through the exploitation of the aerodynamic interaction between the upper atmosphere and an example entry vehicle and remote-sensing orbital platform. Employing the X-37B Orbital Test Vehicle (OTV) and a notional satellite design as the example entry vehicles, the entry profile dynamics of a skip entry maneuver were characterized with varying trajectory initial conditions such as entry altitude, entry flight-path angle, and vehicle aerodynamics. …

Photogrammetric Measurement Of Recession Rates Of Low Temperature Ablators Subjected To High Speed Flow, David W. Callaway

Theses and Dissertations

This research advances a technique to simulate high temperature/high speed effects in a high speed/low temperature environment and to capture recession of the test article in three-dimensions. A method of fabricating dry ice test articles was developed, and the AFIT Mach 3 pressure-vacuum wind tunnel was used in combination with the dry ice test articles to collect three-dimensional ablation data for models of different shapes at stagnation pressures ranging from approximately 0.4 atm to 3 atm and stagnation temperatures equivalent to room temperature. High speed Schlieren photography was used for visualization, and the three dimensional shape change was quantified with …

Optical Flow-Based Odometry For Underground Tunnel Exploration, Terra Kier

Theses and Dissertations

As military operations in degraded or GPS-denied environments continue to increase in frequency and importance, there is an increased necessity to be able to determine precision location within these environments. Furthermore, authorities are finding a record number of tunnels along the U.S.-Mexico border; therefore, underground tunnel characterization is becoming a high priority for U.S. Homeland Security as well. This thesis investigates the performance of a new image registration technique based on a two camera optical- flow configuration using phase correlation techniques. These techniques differ from other image based navigation methods but present a viable alternative increasing autonomy and answering the …

Study Of Varying Boundary Layer Height On Turret Flow Structures, Renato Jelic

Theses and Dissertations

The Air Force Institute of Technology and the Air Force Research Labs are investigating flows over turrets which are commonly encountered in directed energy integrations with air vehicles. In this work, the computational study was performed using the NASA developed time-marching finite volume code OVERFLOW 2.2 to analyze the effect of boundary layer height on symmetrical and non-symmetrical turret geometries. The effects of aerodynamics yield to the aberration of the laser beam through two methods, aero-optical and aero-mechanical jitter. The analysis of the flow features, pressure fluctuations, density fluctuations, and forces and moments on the various geometries was conducted to …

A Relay-Rover Differential Game, Youngdong Choi

Theses and Dissertations

Guidance laws are developed to optimally position a relay Micro-UAV (MAV) to provide an operator at the base with real-time Intelligence, Surveillance, and Reconnaissance (ISR) by relaying communication and video signals when the rover MAV performing the ISR mission is out of radio contact range with the base. The ISR system is comprised of two MAVs, the Relay and the Rover, and a Base. The Relay strives to minimize the radio frequency (RF) power required for maintaining communications, while the Rover performs the ISR mission, which may maximize the required RF power. The optimal control of the Relay MAV entails …

Simulations For The Test Flight Of An Experimental Hale Aircraft, Brooke E. Kaszynski

Theses and Dissertations

Recent events, such as the crash of NASA's Helios aircraft during a test flight, show that more must be known about the nonlinear control of HALE aircraft. Shearer, Cesnik and their co-workers have developed a code that is a practical solution to the coupled nonlinear aeroelasticity and flight dynamics of very flexible aircraft called the University of Michigan's Nonlinear Aeroelastic Simulation Toolbox (UM/NAST). They are also in the process of developing a model HALE aircraft called X-HALE which will be used to validate this code experimentally. This research performs flight simulations with UM/NAST so as to make predictions about X-HALE's …

Operational Characteristics Of A Rotating Detonation Engine Using Hydrogen And Air, Rachel M. Russo

Theses and Dissertations

Rotating detonation engines (RDE) are pressure gain combustion engines that have the potential for greater efficiency than traditional, constant pressure, deflagration engines. RDEs are smaller and mechanically simpler than pulsed detonation engines. A small diameter (3 in) engine was successfully run on hydrogen and air. Most of the tests were conducted using air with a slightly lower diluents percentage (77% nitrogen as opposed to 79% nitrogen). These tests provided the foundation for determining the operational space (mass flow rate and equivalence ratio) of the rotating detonation engine. From the tests conducted with the lower diluents air, the appropriate run conditions …

Process For Refining And Validating A Finite Element Model Of An Experimental High-Altitude, Long-Endurance (Hale) Aircraft, Nicholas A. Sinnokrak

Theses and Dissertations

The work presented here focuses on finite element (FE) modeling of X-HALE, a test aircraft designed and built by the University of Michigan, in conjunction with the Air Force Institute of Technology (AFIT) and Air Force Research Laboratory (AFRL). This scaled vehicle is representative of high-altitude, long-endurance (HALE) aircraft and was designed to provide controlled aeroelastic and flight data. FE models of portions of the X-HALE wing structure were created and analysis results were compared against two separate laboratory static bending tests conducted on X-HALE wing sections. The process documented here should improve future efforts to refine FE models of …

Design And Characterization Of A Space Based Chromotomographic Hyperspectral Imaging Experiment, Jason D. Niederhauser

Theses and Dissertations

This research focuses upon the design, analysis and characterization of several systems related to a spacebased chromotomographic experiment (CTEx), a hyperspectral imager, currently in development at the Air Force Institute of Technology. Three interrelated subject-areas were developed. The initial focal point was a generic, system-level mechanical layout and integration analysis of the space-based instrument. The scope of this work was intended to baseline the space-based system design in order to allow for further trade-space refinement and requirements development. Second, development of an iteration upon the ground-based version of CTEx was accomplished in an effort to support higher-fidelity field data-collection. This …

Solar Warning Architecture For Manned Missions To Mars, James S. Bohren, John K. Howard

Theses and Dissertations

Solar radiation storms represent a dire threat to manned interplanetary space travel. Earth's current solar forecasting architecture is Earth-focused and insufficient to provide timely warnings to a manned mission to Mars, therefore a "best value" solar warning architecture must be identified. A total of 14 solar warning architectures were developed by varying 5 solar sensor locations, 2 processing locations, and 2 communications strategies. Using Satellite Tool Kit, performance of the candidate architectures in terms of Warning Time and Solar Coverage was quantified during a Mars mission scenario based on NASA's Design Reference Architecture 5.0. Cost of each candidate architecture was …

Effect Of Molecular Film Thickness On Thermal Conduction Across Solid-Film Interfaces, Zhi Liang, Hai-Lung Tsai

Mechanical and Aerospace Engineering Faculty Research & Creative Works

The Brownian Motion and Aggregation of Particles in Nanofluids Often Lead to the Formation of Solid-Film-Solid Structures. the Molecular Thin Film Confined between Nanoparticles May Have Non-Negligible Effects on Thermal Conduction among Nanoparticles. using Nonequilibrium Molecular Dynamics Simulations, We Study Thermal Conduction Across the Ag Particle-Ar Thin-Film Interface. If the Film Contains Only One Molecular Layer, We Find that the Solid-Film Interfacial Thermal Resistance RSF is About 1 Order of Magnitude Smaller Than the Solid-Liquid (Bulk) Interfacial Thermal Resistance RSL. If There Are Two or More Molecular Layers in the Film, It is Shown that RSF Increases Rapidly toward RSL …

The Effects Of Damage Arrestment Devices In Composite Plate Sandwiches With Fastener Holes, Mark Anderson, Nancy Hung Choy, Lacey Jones, Rita Kourskaya

Aerospace Engineering

Composite materials such as a carbon fiber are used in a variety of new technologies including aircraft, spacecraft, and motor vehicles. Carbon fiber has a high strength to weight ratio, a key advantage over other material options. This report discusses the use of composite damage arrestment devices (DADs) in composite sandwich panels with a foam core. There are three different curing cycles tested for the DADs: pressure only, vacuum only, and vacuum with 1000 lbs of pressure. Using a Tetrahedron Heat Press to cure the composite specimen and an Instron Machine to perform tensile testing, data was collected for each …

Composite I-Beam Fabrication And Testing In Response To 14th Annual Sampe Bridge Competition, Kodi Rider, Niño Noel Las Piñas, Hans Mayta

Aerospace Engineering

Composites are a type of material that generally combines two materials yielding mechanical properties that are different than its constituent parts. These constituents are classified as either a fiber or a matrix. The objective of this project is to create a carbon-fiber composite I-beam that meets the specifications of the SAMPE student bridge competition. The I-beam consists of carbon fiber unidirectional and woven laminas, as well as aluminum honeycomb and high density polystyrene foam to stiffen the structure. The bridge contest rules limit the dimensions and weight of the bridge. The cross-section must be within 4 inches x 4 inches …

Thermal Analysis Of The Cubesat Cp3 Satellite, Jonas Friedel, Sean Mckibbon

Aerospace Engineering

Due to inconsistencies found in the on-orbit thermal data from the CubeSat CP3 satellite between 2007 and 2011, further analysis is performed on a larger number of data from August 2010 through April 2011, aiming to find an explanation for the overall increasing measured temperatures and shortening peak periods. Therefore, the satellite power data as well as orbital anomalies are analyzed leading to the conclusion that the satellite was temporarily (January – March 2011) orbiting with significantly increased sun exposure causing the higher temperatures. The shortened temperature peak periods are explained by alternating albedo values as the main influence in …

Determination Of The Surface Boundary Layer Using A Quadrotor, Andrew Haviland

Aerospace Engineering

Wind velocity data was taken by a quadrotor UAV using accelerometers, gyroscope, and a barometer. Data was taken at different altitudes over a single position to determine the boundary layer at the surface of the earth. The data taken was compared to the results from numerical methods to determine if this is a practice application for a quadrotor. A few weeks before the test was set to get underway, the quadrotor suffered a very hard crash while testing the GPS and altitude hold function and wasn’t able to completely recover from it. Theoretical results and experiment proposal are covered. 

Design, Manufacturing And Testing Of An Environmentally-Green Bipropellant Thruster, Alex Bendoyro, Gabriel Sanchez, Erin Stearns, Phillip Takahashi

Aerospace Engineering

This project reviews the design, manufacturing and experimentation process of a green bi-propellant thruster designed to output 5 lbf. The goals were to successfully design, manufacture and test a thruster, while discovering the complications that arise through out the complete design process of a green thruster. The thruster was successfully designed using ideal rocket equations and the design was successfully confirmed using CFD and FEA. Manufacturing of the thruster was fully planned and revealed mild flaws in thruster design. For example some features were not manufacturable to the exact measurements desired. Testing of the engine gave results inconsistent with expected …

Numerical Modeling Of The Cn Spectral Emission Of The Stardust Re-Entry Vehicle, Alexandre Martin, Erin D. Farbar, Iain D. Boyd

Mechanical Engineering Faculty Publications

Re-entry vehicles designed for space exploration are usually equipped with thermal protection systems made of ablative material. In order to properly model and predict the aerothermal environment of the vehicle, it is imperative to account for the gases produced by ablation processes. In the case of charring ablators, where an inner resin is pyrolyzed at a relatively low temperature, the composition of the gas expelled into the boundary layer is complex and may lead to thermal chemical reactions that cannot be captured with simple ow chemistry models. In order to obtain better predictions, an appropriate gas ow chemistry model needs …