<p> Astronaut hand fatigue during Extravehicular Activity (EVA) and EVA training is a critical risk in human space exploration. Improved glove designs over the past forty years have reduced hand fatigue, but limitations of the technology prevent major improvements to reduce hand fatigue. Therefore, a mechanism to assist astronauts by reducing hand fatigue was explored. Many organizations have already developed exoskeletons to assist astronauts, but all mechanisms developed required electrically powered actuators and control systems to enhance grip strength. However, astronauts already possess the strength required to actuate the glove; what is needed is a method to reduce fatigue without introducing electromechanical complexity. A passive mechanical system was developed as a proof-of-concept to test the feasibility of an unpowered exoskeleton to maintain static grip around an object. The semi- rigid nature of an inflated pressure glove provided an ideal substrate to mount a mechanism and associated components to allow an astronaut to release his/her grip inside the glove while maintaining attitude, as the mechanism will keep the glove closed around an object.</p><p> Three prototypes were fabricated and tested to evaluate the architecture. The final two prototypes were tested on a real pressure suit glove at Final Frontier Design (FFD), and the third mechanism demonstrated attachment and basic operating principles. At University of California (UC) Davis, pressure glove analogs were fabricated from a baseball batting glove and polystyrene to simulate a real pressure glove without the risk of testing in a reduced pressure environment (i.e. a glove box). Testing of the third prototype showed a reduction in fatigue as measured by Maximum Voluntary Contraction (MVC) grip force over a 30 second period when the mechanism assisted gripping an object.</p>

<p>The most common traditional non-functional requirement analysis is reliability. With systems becoming more complex, networked, and adaptive to environmental uncertainties, system resiliency has recently become the non-functional requirement analysis of choice. Analysis of system resiliency has challenges; which include, defining resilience for domain areas, identifying resilience metrics, determining resilience modeling strategies, and understanding how to best integrate the concepts of risk and reliability into resiliency. Formal methods that integrate all of these concepts do not currently exist in specific domain areas. Leveraging RAMSoS, a model-based reliability analysis methodology for Systems of Systems (SoS), we propose an extension that accounts for resiliency analysis through evaluation of mission performance, risk, and cost using multi-criteria decision-making (MCDM) modeling and design trade study variability modeling evaluation techniques. This proposed methodology, coined RAMSoS-RESIL, is applied to a case study in the multi-agent unmanned aerial vehicle (UAV) domain to investigate the potential benefits of a mission architecture where functionality to complete a mission is disseminated across multiple UAVs (distributed) opposed to being contained in a single UAV (monolithic). The case study based research demonstrates proof of concept for the proposed model-based technique and provides sufficient preliminary evidence to conclude which architectural design (distributed vs. monolithic) is most resilient based on insight into mission resilience performance, risk, and cost in addition to the traditional analysis of reliability.

High-speed impinging jets are often generated by the propulsive systems of aerospace launch vehicles and tactical aircraft. In many instances, the presence of these impinging jets creates a hazard for flight operations personnel due to the extremely high noise levels and unsteady loads produced by fluid-surface interaction. In order to effectively combat these issues, a fundamental understanding of the flow physics and dominant acoustic behavior is essential. There are inherent challenges in performing such investigations, especially with the need to simulate the flowfield under realistic operational conditions (temperature, Mach number, etc.) and in configurations that are relevant to full-scale application. A state-of-the-art high-temperature flow facility at Florida State University has provided a unique opportunity to experimentally investigate the high-speed impinging jet flowfield at application-relevant conditions. Accordingly, this manuscript reports the findings of several experimental studies on high-temperature supersonic impinging jets in multiple configurations. The overall objective of these studies is to characterize the complex relationship between the hydrodynamic and acoustic fields. A fundamental parametric investigation has been performed to document the flowfield and acoustic characteristics of an ideally-expanded supersonic air jet impinging onto a semi-infinite flat plate at ambient and heated jet conditions. The experimental program has been designed to span a widely-applicable geometric parameter space, and as such, an extensive database of the flow and acoustic fields has been developed for impingement distances in the range 1d to 12d, impingement angles in the range 45 degrees to 90 degrees, and jet stagnation temperatures from 289K to 811K (TTR=1.0 to 2.8). Measurements include point-wise mean and unsteady pressure on the impingement surface, time-resolved shadowgraphy of the flowfield, and fully three-dimensional near field acoustics. Aside from detailed documentation of the flow and acoustic fields, this work aims to develop a physical understanding of the noise sources generated by impingement. Correlation techniques are employed to localize and quantify the spatial extent of broadband noise sources in the near-impingement region and to characterize their frequency content. Additionally, discrete impingement tones are documented for normal and oblique incidence angles, and an empirical model of the tone frequencies has been developed using velocity data extracted from time-resolved shadowgraphy together with a simple modification to the conventional feedback formula to account for non-normal incidence. Two application-based studies have also been undertaken. In simulating a vertical take-off and landing aircraft in hover, the first study of a normally-impinging jet outfitted with lift-plate characterizes the flow-acoustic interaction between the high-temperature jet and the underside of an aircraft and documents the effectiveness of an active flow control technique known as `steady microjet injection' to mitigate high noise levels and unsteady phenomena. The second study is a detailed investigation of the jet blast deflector/carrier deck configuration aimed at gaining a better understanding of the noise field generated by a jet operating on a flight deck. The acoustic directionality and spectral characteristics are documented for a model-scale carrier deck with particular focus on locations that are pertinent to flight operations personnel. / A Dissertation submitted to the Department of Mechanical Engineering in partial fulfillment of the requirements for the degree of Doctor of Philosophy. / Summer Semester 2017. / June 23, 2017. / acoustic, aeroacoustic, flow noise, impingement, jet, supersonic / Includes bibliographical references. / Farrukh Alvi, Professor Co-Directing Dissertation; Chiang Shih, Professor Co-Directing Dissertation; Richard Liang, University Representative; Emmanuel Collins, Committee Member; Jonas Gustavsson, Committee Member; Rajan Kumar, Committee Member; Krista Michalis, Committee Member.

In this study, the flow and acoustic field characteristics of dual high-speed axi-symmetric impinging jets will be examined. Initially, the short takeoff and vertical landing (STOVL) facility was redesigned by adding a second jet to the existing model there by achieving a dual jet configuration. This modified facility was designed to simulate aircraft hover in proximity to the ground. Emphasis is placed on the complex behavior of the jets as the nozzle pressure ratio (NPR) is varied to produce over-expanded, ideally-expanded and under-expanded jet flows. Two nozzle configurations were chosen to simulate dual impinging jets: 1) two converging nozzles (Mach design, Md = 1.00) and 2) a converging nozzle (Md = 1.00) and a converging-diverging (CD) nozzle (Md = 1.50). The experimental results described in this thesis include shadowgraph flow visualization, surface pressure measurements, and near-field acoustic measurements. Shadowgraph flow visualization was used to observe the acoustic field and the coupling between dual jets for various NPR combinations. Mean surface pressure measurements were obtained for impinging jet configurations which analyzed the jet behavior for ground plane separations ranging from x/D = 2 to 10. These measurements provided information regarding the footprint of the flow-field, particularly the fountain flow behavior. It was found that there is a shift in the fountain flow region which occurs when the NPR of one jet was substantially higher than the supplementary jet. Unsteady pressure measurements and near-field acoustic measurements investigated the presence of a feedback loop that occurs for both free and impinging jets, under certain conditions. The presence of tones, either screech or impingement, was clearly evident from the spectral peaks in the near-field noise spectra. When such tones are present, the corresponding flow-field images show strong acoustic waves. / A Thesis submitted to the Department of Mechanical Engineering in partial fulfillment of the requirements for the degree of Master of Science. / Summer Semester 2017. / June 20, 2017. / Characterization, Dual, FCAAP, Impinging, Malcolm, Thesis / Includes bibliographical references. / Farrukh Alvi, Professor Directing Thesis; Rajan Kumar, Committee Member; Emmanuel Collins, Committee Member.

<p> The discipline of systems engineering continues to increase in importance. There are more projects, projects are larger, and projects are more critical, and all of these mean that more and better systems engineering is required. It follows that the cost of systems engineering continues to increase in importance. In turn, it follows that accurate estimation of systems engineering costs continues to increase in importance, as systems engineering results suffer if a project either underestimates or overestimates its cost. </p><p> There are models for estimating systems engineering cost, notably COSYSMO 1.0, but all these models leave out some aspect of modern practices, and therefore tend to estimate a modern systems engineering cost inaccurately, or not at all. These modern practices include reuse of engineering artifacts, requirements volatility, and engineering in a system-of-systems context. While all of these practices have been addressed to some extent in research papers, there is no all-encompassing model that integrates all of them. </p><p> My research has resulted in an integrated model that includes the features of COSYSMO 1.0 and covers those modern practices. It is open and therefore widely available. I have completed a comprehensive model based, in part, on actual project data.</p><p>

abstract: In recent years, a new type of ionic salt based solid propellant, considered inert until the application of an electric current induces an electro-chemical reaction, has been under investigation due to its broad range of possible uses. However, while many electric propellant formulations and applications have been explored over the years, a fundamental understanding of the operational mechanisms of this propellant is necessary in order to move forward with development and implementation of this technology. It has been suggested that the metallic additive included in the formulation studied during this investigation may be playing an additional, currently unknown role in the operation and performance of the propellant. This study was designed to examine variations of an electric propellant formulation with the purpose of investigating propellant bulk volume electrical resistivity in order to attempt to determine information regarding the fundamental science behind the operation of this material. Within a set of fractional factorial experiments, variations of the propellant material made with tungsten, copper, carbon black, and no additive were manufactured using three different particle size ranges and three different volume percentage particle loadings. Each of these formulations (a total of 21 samples and 189 specimens) were tested for quantitative electrical resistivity values at three different pulse generator input voltage values. The data gathered from these experiments suggests that this electric propellant formulation’s resistivity value does change based upon the included additive. The resulting data has also revealed a parabolic response behavior noticeable in the 2D and 3D additive loading percentage versus additive particle size visualizations, the lowest point of which, occurring at an approximately 2.3% additive loading percentage value, could be indicative of the effects of the percolation phenomena on this material. Finally, the investigation results have been loosely correlated to power consumption testing results from previous work that may indicate that it is possible to relate propellant electrical resistivity and operating requirements. Throughout this study, however, it is obvious based on the data gathered that more information is required to be certain of these conclusions and in order to fully understand how this technology can be controlled for future use. / Dissertation/Thesis / Masters Thesis Mechanical Engineering 2019

This thesis reports on research into the causes of local optima when optimization algorithms are applied to aerospace structural design. A thorough understanding of local optima will enable the engineers to select the algorithm for optimization or to guide the optimization to ensure either global optima or near optimal solutions are achieved. Therefore, a comprehensive literature review has been conducted and several illustrative examples have been identified to help fully understand the cause and importance of local optima. The first application involved the design of the internal structure of a simplified wing spoiler. MSC.NASTRAN was used to optimize each discretized location of an additional rib with the aid of a Patran Command Language (PCL) algorithm. The objective function of minimum weight was approximated as a multimodal function in a 2D smooth curve where the local and global optima were identified. The theory of continuous rectangular plates was used to explain the phenomena. The second problem considered buckling of a wing rib. A PCL code was written to obtain the rib buckling factors as the position of the center of a square cutout was varied within a constrained area. The rib linear buckling factor versus the centre position O(X, Y) of the square cutout was plotted in a 3D surface contour plot. Load path theory and relevant plate buckling theories were used to explain the local and global maxima identified. The final example considered the maximization of the buckling load of a simply supported composite laminated plate under in-plane loading. A conventional Genetic Algorithm was used to examine the local and global optima of the critical buckling load factor. Many local and global optima were identified and explained and many near-optimal solutions were found in a single run. A significant understanding of local optima in aerospace structural design with the optimal utilization of available software and the appropriate selection of optimization algorithms has been achieved. Further work could either include implementing the proposed global optimization strategies or include implementing rapid methods for identifying multiple local optima.

Non-conventional bio-derived fuels have been evaluated for use in hybrid rocket motors. Tests were conducted at combustion pressures in the range of 100 – 220 psig and thrust levels of 40 – 170 newtons. Beeswax was tested with oxygen as the oxidizer and showed a regression rate at least three times as high as traditional hybrid propellant combinations such as hydroxyl-terminated polybutadiene (HTPB) and liquid oxygen (LOX). This provides the promise of a high thrust hybrid rocket motor using a simple, single port geometry and overcomes the main weakness of traditional hybrid rocket motor propellants, which are low regression rates. Beeswax was also tested with nitrous oxide as an oxidizer, but further testing is needed to attain high enough combustion chamber pressures to achieve stable combustion. Experimental evaluation of the specific impulse for beeswax and oxygen was moderately successful for lab scale testing, but needs further refinement. Analytical studies were performed to evaluate the theoretical performance of non-conventional hybrid rocket motors. This analysis indicates beeswax, lard, a mixture of paraffin and lard, and combinations of beeswax and aluminum should all perform better than traditional hybrid rocket propellants considered when burned with oxygen. For a combustion chamber pressure of 500.38 psig, beeswax and oxygen yielded a maximum specific impulse of 327 s. The high specific impulse combined with a high regression rate combine to make beeswax and oxygen a potentially high performing hybrid rocket motor propellant for launch vehicles, suborbital rockets, or orbital kick motors.

Thesis (M.App.Sc.) - Carleton University, 2009. / Includes bibliographical references (p.153-159). Also available in electronic format on the Internet.

Thesis (M.S.)--Rutgers University, 2009. / "Graduate Program in Mechanical and Aerospace Engineering." Includes bibliographical references (p. 78-81).