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6,065 full-text articles. Page 7 of 198.

Tumble Bot, Alena Beyer, Blake Gonzales, Jensen Severance, Liam Chaffey 2019 California Polytechnic State University, San Luis Obispo

Tumble Bot, Alena Beyer, Blake Gonzales, Jensen Severance, Liam Chaffey

Mechanical Engineering

Passive locomotion is the ability for an object to move from one place to another by the means of the environment. In nature species such as tumbleweed, fox tails, plankton, and man o’ war jellyfish rely on passive modes of transportation for survival and are able to cross vast distances with little to no expenditure of their own energy. This document seeks to explore the feasibility of building a machine relies on the energy of Mars’ environment to explore the Martian surface.

The “Tensegrity Tumbleweed Locomotion” (nicknamed Tumble Bot) senior project was sponsored by NASA Jet Propulsion Laboratory (JPL). The ...


Fuel Efficient Control Design And Constrained Motion Analysis For Spacecraft Coloumb Formation In Elliptic Chief Orbits, Muhammad Wasif Memon 2019 Embry-Riddle Aeronautical University

Fuel Efficient Control Design And Constrained Motion Analysis For Spacecraft Coloumb Formation In Elliptic Chief Orbits, Muhammad Wasif Memon

Dissertations and Theses

The use of Coulomb force has been analyzed in recent years to provide propulsion in space for various applications. Coulomb formation can also be utilized to make close formation spacecraft missions fuel efficient. In this study, the Coulomb formation of two craft is studied in elliptic chief orbits for two formation geometries. The first formation requires both spacecraft to be aligned along the nadir (radial) direction and the second formation requires both spacecraft to maintain a constant separation distance relative to each other while each spacecraft rotates freely on the surface of a sphere with the ratio of the radii ...


Development Of A Research Spacecraft Test-Bed With Implementation Of Control Laws To Compensate Undesired Dynamics, Yomary Angélica Betancur Vesga 2019 Embry-Riddle Aeronautical University

Development Of A Research Spacecraft Test-Bed With Implementation Of Control Laws To Compensate Undesired Dynamics, Yomary Angélica Betancur Vesga

Dissertations and Theses

The development of research spacecraft systems has a significant impact on the preparation and simulation of future space missions. Hardware, software and operation procedures can be adequately tested, validated and verified before they are deployed for the actual mission. In this thesis, a spacecraft vehicle test-bed named Extreme Access System (EASY) was developed. EASY aims at supporting validation and verification of guidance, navigation and control algorithms. Description of EASY spacecraft systems, sub-systems and integration is presented in this thesis along with an analysis of results from numerical simulation and actual implementation of control laws. An attitude control architecture based on ...


Droplets As Carriers For Flexible Electronic Devices, Mingxing Zhou, Ziyue Wu, Yicong Zhao, Qing Yang, Wei Ling, Ya Li, Hang Xu, Cheng Wang, Xian Huang 2019 Missouri University of Science and Technology

Droplets As Carriers For Flexible Electronic Devices, Mingxing Zhou, Ziyue Wu, Yicong Zhao, Qing Yang, Wei Ling, Ya Li, Hang Xu, Cheng Wang, Xian Huang

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Coupling soft bodies and dynamic motions with multifunctional flexible electronics is challenging, but is essential in satisfying the urgent and soaring demands of fully soft and comprehensive robotic systems that can perform tasks in spite of rigorous spatial constraints. Here, the mobility and adaptability of liquid droplets with the functionality of flexible electronics, and techniques to use droplets as carriers for flexible devices are combined. The resulting active droplets (ADs) with volumes ranging from 150 to 600 µL can conduct programmable functions, such as sensing, actuation, and energy harvesting defined by the carried flexible devices and move under the excitation ...


Performance Enhancement And Characterization Of An Electromagnetic Railgun, Paul M. Gilles 2019 California Polytechnic State University, San Luis Obispo

Performance Enhancement And Characterization Of An Electromagnetic Railgun, Paul M. Gilles

Master's Theses and Project Reports

Collision with orbital debris poses a serious threat to spacecraft and astronauts. Hypervelocity impacts resulting from collisions mean that objects with a mass less than 1g can cause mission-ending damage to spacecraft. A means of shielding spacecraft against collisions is necessary. A means of testing candidate shielding methods for their efficacy in mitigating hypervelocity impacts is therefore also necessary. Cal Poly’s Electromagnetic Railgun was designed with the goal of creating a laboratory system capable of simulating hypervelocity (≥ 3 km/s) impacts. Due to several factors, the system was not previously capable of high-velocity (≥ 1 km/s) tests. A deficient ...


Dynamic Pressure Sensing For The Flight Test Data System, Marc Y. Goupil 2019 California Polytechnic State University - San Luis Obispo

Dynamic Pressure Sensing For The Flight Test Data System, Marc Y. Goupil

Master's Theses and Project Reports

This thesis describes the design, assembly, and test of the FTDS-K, a new device in the Boundary Layer Data System (BLDS) family of flight data acquisition systems. The FTDS-K provides high-frequency, high-gain data acquisition capability for up to two pressure sensors and an additional three low-frequency pressure sensors. Development of the FTDS-K was separated into a core module, specialized analog subsystem, and practical testing of the FTDS-K in a flow measurement mission. The core module combines an nRF52840-based microcontroller module, switching regulator, microSD card, real-time clock, temperature sensor, and trio of pressure sensors to provide the same capabilities as previous-generation ...


Magnetic Field Induced Ferrofluid Droplet Breakup In A Simple Shear Flow At A Low Reynolds Number, Md Rifat Hassan, Cheng Wang 2019 Missouri University of Science and Technology

Magnetic Field Induced Ferrofluid Droplet Breakup In A Simple Shear Flow At A Low Reynolds Number, Md Rifat Hassan, Cheng Wang

Mechanical and Aerospace Engineering Faculty Research & Creative Works

The breakup phenomenon of a ferrofluid droplet in a simple shear flow under a uniform magnetic field is numerically investigated in this paper. The numerical simulation, based on the finite element method, uses a level set method to capture the dynamic evolution of the droplet interface between the two phases. Focusing on small Reynolds numbers (i.e., Re ≤ 0.03), systematic numerical simulations are carried out to analyze the effects of magnetic field strength, direction, and viscosity ratio on the breakup phenomenon of the ferrofluid droplet. The results suggest that applying a magnetic field along α = 45° and 90° relative ...


Damage Resistance And Tolerance Of 3d Woven Composites, Justin T. McDermott 2019 University of Maine

Damage Resistance And Tolerance Of 3d Woven Composites, Justin T. Mcdermott

Electronic Theses and Dissertations

Composite materials have been adopted into primary aircraft structures by virtue of their great strength-to-weight and stiffness-to-weight ratios, fatigue insensitivity, and corrosion resistance. These characteristics are leveraged by aircraft designers to deliver improved fuel effciency and reduced scheduled maintenance burdens for their customers. These benefits have been impressively realized in the Boeing 787 and Airbus A350 XWB, with airframes utilizing about 50% composites by weight. Tempering these successes, however, are the inherent vulnerabilities of carbon-fiber reinforced composites. When compared to conventional metallic structure, composite laminates are more sensitive to stress concentrations at mechanical fastenings and damage due to low-velocity impact ...


A Reinforcement Learning Approach To Spacecraft Trajectory Optimization, Daniel S. Kolosa 2019 Western Michigan University

A Reinforcement Learning Approach To Spacecraft Trajectory Optimization, Daniel S. Kolosa

Dissertations

This dissertation explores a novel method of solving low-thrust spacecraft targeting problems using reinforcement learning. A reinforcement learning algorithm based on Deep Deterministic Policy Gradients was developed to solve low-thrust trajectory optimization problems. The algorithm consists of two neural networks, an actor network and a critic network. The actor approximates a thrust magnitude given the current spacecraft state expressed as a set of orbital elements. The critic network evaluates the action taken by the actor based on the state and action taken. Three different types of trajectory problems were solved, a generalized orbit change maneuver, a semimajor axis change maneuver ...


Axial Compressor Based On Plastic Additive Manufacturing, Chris Phu 2019 University of Arkansas, Fayetteville

Axial Compressor Based On Plastic Additive Manufacturing, Chris Phu

Mechanical Engineering Undergraduate Honors Theses

Turbomolecular pumps designed to function in very low pressures tend to be too prohibitively expensive for student researchers. On the other hand, while conventional pumps are affordable, they can’t function in extreme low pressures. An additively manufactured axial compressor however is inexpensive to manufacturer and only needs to be build up enough pressure for a conventional pump to function. After many design iterations, a final iteration that is near vacuum chamber ready has been 3D printed and tested for spin functionally. The designed axial compressor is easy to assemble and very modular. Conclusions from each of the design iterations ...


Development And Testing Of A Hydrogen Peroxide Injected Thrust Augmenting Nozzle For A Hybrid Rocket, Mark C. Heiner 2019 Utah State University

Development And Testing Of A Hydrogen Peroxide Injected Thrust Augmenting Nozzle For A Hybrid Rocket, Mark C. Heiner

All Graduate Theses and Dissertations

During a rocket launch, the point at which the most thrust is needed is at lift-off where the rocket is the heaviest since it is full of propellant. Unfortunately, this is also the point at which rocket engines perform the most poorly due to the relatively high atmospheric pressure at sea level. The Thrust Augmenting Nozzle (TAN) investigated in this paper provides a solution to this dilemma. By injecting extra propellant into the nozzle but downstream of the throat, the internal nozzle pressure is raised and the thrust is increased, and the nozzle efficiency, or specific impulse is potentially improved ...


Revolution In Autonomous Orbital Navigation (Raon), Rachit Bhatia 2019 Utah State University

Revolution In Autonomous Orbital Navigation (Raon), Rachit Bhatia

All Graduate Theses and Dissertations

Spacecraft navigation is a critical component of any space mission. Space navigation uses on-board sensors and other techniques to determine the spacecraft’s current position and velocity, with permissible accuracy. It also provides requisite information to navigate to a desired position, while following the desired trajectory. Developments in technology have resulted in new techniques of space navigation. However, inertial navigation systems have consistently been the bedrock for space navigation.

Recently, the successful space mission GOCE used on-board gravity gradiometer for mapping Earth’s gravitational field. This has motivated the development of new techniques like cold atom accelerometers, to create ultra-sensitive ...


Boosting Verification Scalability Via Structural Grouping And Semantic Partitioning Of Properties, Rohit Dureja, Jason Baumgartner, Alexander Ivrii, Robert Kanzelman, Kristin Y. Rozier 2019 Iowa State University

Boosting Verification Scalability Via Structural Grouping And Semantic Partitioning Of Properties, Rohit Dureja, Jason Baumgartner, Alexander Ivrii, Robert Kanzelman, Kristin Y. Rozier

Aerospace Engineering Conference Papers, Presentations and Posters

From equivalence checking to functional verification to design-space exploration, industrial verification tasks entail checking a large number of properties on the same design. State-of-the-art tools typically solve all properties concurrently, or one-at-a-time. They do not optimally exploit subproblem sharing between properties, leaving an opportunity to save considerable verification resource via concurrent verification of properties with nearly identical cone of influence (COI). These high-affinity properties can be concurrently solved; the verification effort expended for one can be directly reused to accelerate the verification of the others, without hurting per-property verification resources through bloating COI size. We present a near-linear runtime algorithm ...


Blade Optimization For Ground Level Low Speed Wind Turbines, Ryan Foster 2019 Kennesaw State University

Blade Optimization For Ground Level Low Speed Wind Turbines, Ryan Foster

Georgia Undergraduate Research Conference (GURC)

Low speed wind turbines can provide inexpensive and clean energy in areas where large scale wind power generation is impractical. The purpose of this research is to explore factors that affect the efficiency of low speed wind turbines. The factors that were tested are span, chord length, angle of twist, taper ratio, average thickness, and sweep angle. The goal is to determine a combination of these variables to enable maximum power extraction from a low wind speed source.These parameters are optimized for the Southeastern region of the United States. NOAA weather data at ground level are used to determine ...


Design And Kinematic Analysis Of A Semi-Compliant Swashplate Mechanism, Niko Giannakakos 2019 Kennesaw State University

Design And Kinematic Analysis Of A Semi-Compliant Swashplate Mechanism, Niko Giannakakos

Georgia Undergraduate Research Conference (GURC)

Compliant mechanisms generate motion through the deformation or deflection of its flexible members rather than the revolute joints utilized in traditional rigid link mechanisms. If a compliant mechanism is designed as a single piece without the need of joints to create relative motion, then it is a monolithic system. If at least one part of the mechanism is flexible and assembled with rigid parts and joints, then it is a partially compliant mechanism. The superiorities of compliant mechanisms over rigid mechanisms are the reduced number of parts required to build the system, simple design, no backlash, no lubrication, less friction ...


Development Of Cislunar Space Logistics Networks For Satellite Constellation Support Using Event-Driven Generalized Multi-Commodity Network Flows, Alexander R. Collins 2019 Air Force Institute of Technology

Development Of Cislunar Space Logistics Networks For Satellite Constellation Support Using Event-Driven Generalized Multi-Commodity Network Flows, Alexander R. Collins

Theses and Dissertations

As space becomes an increasingly congested domain, the risk of damage to satellite constellations is increasing. In response, there is an increasing need for capabilities for unmanned repair, refueling, and reconstitution (R3) of those constellations. Cislunar orbits offer a promising storage and low-cost transfer solution for on-orbit service vehicles and replacement satellites to leverage those capabilities. This research makes use of mixed-integer linear programming-based logistics models to determine the situations in which a cislunar mission architecture would offer a cost-effective alternative to Earth-based R3. The network models presented in this research make use of the latest developments in Event-Driven Generalized ...


Designing Wind Turbine Rotor Blades To Enhance Energy Capture In Turbine Arrays, Benham Moghadassian, Anupam Sharma 2019 Iowa State University

Designing Wind Turbine Rotor Blades To Enhance Energy Capture In Turbine Arrays, Benham Moghadassian, Anupam Sharma

Aerospace Engineering Publications

An inverse design approach is proposed to compute wind turbine blade geometries which maximize the aggregate power output from a wind farm. An iterative inverse algorithm is used to solve the optimization problem. The algorithm seeks to minimize the target function, f = -CP,av, where CP,av is the average normalized mechanical power of all the turbines in the wind farm. An upper bound on the blade planform area, representative of the blade weight, is imposed to demonstrate how to incorporate constraints in the design process. The power coefficients (CP) of the turbines in the farm are ...


Influence Of Flow Rate, Nozzle Speed, Pitch And The Number Of Passes On The Thickness Of S1805 Photoresist In Suss Microtec As8 Spray Coater, Rohan Sanghvi, Gyuseok Kim 2019 Singh Center for Nanotechnology

Influence Of Flow Rate, Nozzle Speed, Pitch And The Number Of Passes On The Thickness Of S1805 Photoresist In Suss Microtec As8 Spray Coater, Rohan Sanghvi, Gyuseok Kim

Tool Data

S1805 positive photoresist has been deposited on single crystalline Si wafers using a Suss MicroTec Alta Spray. The influence of flow rate, nozzle speed, pitch and number of passes on the thickness of the photoresist was studied. Results show that the thickness of S1805 is linearly proportional to the flow rate and number of passes, and inversely proportional to the nozzle speed and pitch.


Gelatine Cavity Dynamics Of High-Speed Sphere Impact, Akihito Kiyama, Mohammad M. Mansoor, Nathan B. Speirs, Yoshiyuki Tagawa, Tadd T. Truscott 2019 Tokyo University of Agriculture and Technology

Gelatine Cavity Dynamics Of High-Speed Sphere Impact, Akihito Kiyama, Mohammad M. Mansoor, Nathan B. Speirs, Yoshiyuki Tagawa, Tadd T. Truscott

Mechanical and Aerospace Engineering Faculty Publications

We investigate the impact and penetration of a solid sphere passing through gelatine at various impact speeds up to 143.2 m s-1 Tests were performed with several concentrations of gelatine. Impacts for low elastic Froude number Fre a ratio between inertia and gelatine elasticity, resulted in rebound. Higher Fre values resulted in penetration, forming cavities with prominent surface textures. The overall shape of the cavities resembles those observed in water-entry experiments, yet they appear in a different order with respect to increasing inertia: rebound, quasi-seal, deep-seal, shallow-seal and surface-seal. Remarkably, similar to the WeBo phase ...


Validation Of Rhocentralfoam For Engineering Applications Of Under-Expanded Impinging Free Jets, Peter Nielsen 2019 The University of Western Ontario

Validation Of Rhocentralfoam For Engineering Applications Of Under-Expanded Impinging Free Jets, Peter Nielsen

Electronic Thesis and Dissertation Repository

A numerical validation study of under-expanded impinging jet is conducted using OpenFOAM, an open-source computational fluid dynamics (CFD) library. RhoCentralFoam, a density based, compressible flow solver with a two-equation shear stress transport (SST) turbulence model is used on an axisymmetric model to reduce the computation cost. Major features of the flow were compared to an experimental study by Henderson et al., with a nozzle pressure ratio (NPR) of 4.0 and nozzle to plate spacing between 1.65-4.16. Of the features measured, the Mach diamond spacing, super-sonic core, and shear layer are all accurately predicted, while the recirculation bubble ...


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