• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 86
  • 24
  • 9
  • 8
  • 2
  • 1
  • 1
  • 1
  • 1
  • 1
  • 1
  • 1
  • Tagged with
  • 180
  • 57
  • 53
  • 21
  • 18
  • 18
  • 17
  • 17
  • 14
  • 14
  • 13
  • 13
  • 12
  • 12
  • 12
  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
151

Planning concepts to sustain, develop, and test complex naval combat systems at the Surface Combat Systems Center, Wallops Island, Virginia

Abell, Barry J. 03 1900 (has links)
Approved for public release, distribution is unlimited / The Surface Combat Systems Center (SCSC), Wallops Island, Virginia is a combination of personnel, geography, airspace, and technology located on a barrier island off Virginia's Eastern Shore. First opened in 1985 as a US Navy, AEGIS Land-Based Test Site (LBTS), SCSC has grown to include the Ship Self Defense (SSD), and DD(X) combat system facilities to the site. SCSC is chartered to support computer program development, life cycle and in-service engineering, team training, and research, development, test, and evaluation services while adapting to evolution of US Naval combatants and emerging requirements. The purpose of this document is to present an analysis of existing US Navy shipboard and land-based organization business practices and apply them to the existing SCSC command organization. The objective is to combine US Navy transformation concepts and SCSC planning concepts to provide the documentation needed to support the development of new strategic business plans for the command. The goal is to provide a long-term strategy to transform SCSC into the US Navy's East Coast Weapons Range Facility or otherwise named, the Wallops Island Test and Evaluation Range Facility (WITERF), while maintaining its synergy as a LBTS for research, development, testing and evaluation of naval combat systems. / Civilian, United States Navy
152

A Markovian state-space framework for integrating flexibility into space system design decisions

Lafleur, Jarret Marshall 16 December 2011 (has links)
The past decades have seen the state of the art in aerospace system design progress from a scope of simple optimization to one including robustness, with the objective of permitting a single system to perform well even in off-nominal future environments. Integrating flexibility, or the capability to easily modify a system after it has been fielded in response to changing environments, into system design represents a further step forward. One challenge in accomplishing this rests in that the decision-maker must consider not only the present system design decision, but also sequential future design and operation decisions. Despite extensive interest in the topic, the state of the art in designing flexibility into aerospace systems, and particularly space systems, tends to be limited to analyses that are qualitative, deterministic, single-objective, and/or limited to consider a single future time period. To address these gaps, this thesis develops a stochastic, multi-objective, and multi-period framework for integrating flexibility into space system design decisions. Central to the framework are five steps. First, system configuration options are identified and costs of switching from one configuration to another are compiled into a cost transition matrix. Second, probabilities that demand on the system will transition from one mission to another are compiled into a mission demand Markov chain. Third, one performance matrix for each design objective is populated to describe how well the identified system configurations perform in each of the identified mission demand environments. The fourth step employs multi-period decision analysis techniques, including Markov decision processes (MDPs) from the field of operations research, to find efficient paths and policies a decision-maker may follow. The final step examines the implications of these paths and policies for the primary goal of informing initial system selection. Overall, this thesis unifies state-centric concepts of flexibility from economics and engineering literature with sequential decision-making techniques from operations research. The end objective of this thesis' framework and its supporting analytic and computational tools is to enable selection of the next-generation space systems today, tailored to decision-maker budget and performance preferences, that will be best able to adapt and perform in a future of changing environments and requirements. Following extensive theoretical development, the framework and its steps are applied to space system planning problems of (1) DARPA-motivated multiple- or distributed-payload satellite selection and (2) NASA human space exploration architecture selection.
153

The application of systems engineering to a Space-based Solar Power Technology Demonstration Mission

Chemouni Bach, Julien 07 June 2012 (has links)
This thesis presents an end-to-end example of systems engineering through the development of a Space-based Solar Power Satellite (SSPS) technology demonstration mission. As part of a higher education effort by NASA to promote systems engineering in the undergraduate classroom, the purpose of this thesis is to provide an educational resource for faculty and students. NASA systems engineering processes are tailored and applied to the development of a conceptual mission in order to demonstrate the role of systems engineering in the definition of an aerospace mission. The motivation for choosing the SSPS concept is two fold. First, as a renewable energy concept, space-based solar power is a relevant topic in today's world. Second, previous SSPS studies have been largely focused on developing full-scale concepts and lack a formalized systems engineering approach. The development of an SSPS technology demonstration mission allows for an emphasis on determining mission, and overall concept, feasibility in terms of technical needs and risks. These are assessed through a formalized systems engineering approach that is defined as an early concept or feasibility study, typical of Pre-Phase A activities. An architecture is developed from a mission scope, involving the following trade studies: power beam type, power beam frequency, transmitter type, solar array, and satellite orbit. Then, a system hierarchy, interfaces, and requirements are constructed, and cost and risk analysis are performed. The results indicate that the SSPS concept is still technologically immature and further concept studies and analyses are required before it can be implemented even at the technology demonstration level. This effort should be largely focused on raising the technological maturity of some key systems, including structure, deployment mechanisms, power management and distribution, and thermal systems. These results, and the process of reaching them, thus demonstrate the importance and value of systems engineering in determining mission feasibility early on in the project lifecycle. / text
154

Contextualization of Autonomous Spaceflight Operations for deep space planetary encounters

Marcinkowski, Michal January 2018 (has links)
This work concerns the research and application of data visualization techniques to depict ongoing activities in mankind’s investigation of space as part of a larger open-source visualization- and science-outreach software known as OpenSpace. It involves the construction of a physically accurate virtual environment of our local star group and solar system so as to facilitate development of a robust and generalized solution capable of articulating mission-science to its viewers. The research part is focused on deploying data visualization methods suitable for contextualizing scientific findings towards the general public in a pedagogical manner, with the end goal to provide a fully operational New Horizons visualization on the day of encounter with Pluto for the first public broadcast of OpenSpace across the globe.
155

Dynamic Visualization of Space Weather Simulation Data / Dynamisk visualisering av rymdvädersimuleringsdata

Sand, Victor January 2014 (has links)
The work described in this thesis is part of the Open Space project, a collaboration between Linköping University, NASA and the American Museum of Natural History. The long-term goal of Open Space is a multi-purpose, open-source scientific visualization software. The thesis covers the research and implementation of a pipeline for preparing and rendering volumetric data. The developed pipeline consists of three stages: A data formatting stage which takes data from various sources and prepares it for the rest of the pipeline, a pre-processing stage which builds a tree structure of of the raw data, and finally an interactive rendering stage which draws a volume using ray-casting. The pipeline is a fully working proof-of-concept for future development of Open Space, and can be used as-is to render space weather data using a combination of suitable data structures and an efficient data transfer pipeline. Many concepts and ideas from this work can be utilized in the larger-scale software project.
156

Design and Implementation of an Out-of-Core Globe Rendering System Using Multiple Map Services / Design och Implementering av ett Out-of-Core Globrenderingssystem Baserat på Olika Karttjänster

Bladin, Kalle, Broberg, Erik January 2016 (has links)
This thesis focuses on the design and implementation of a software system enabling out-of-core rendering of multiple map datasets mapped on virtual globes around our solar system. Challenges such as precision, accuracy, curvature and massive datasets were considered. The result is a globe visualization software using a chunked level of detail approach for rendering. The software can render texture layers of various sorts to aid in scientific visualization on top of height mapped geometry, yielding accurate visualizations rendered at interactive frame rates. The project was conducted at the American Museum of Natural History (AMNH), New York and serves the goal of implementing a planetary visualization software to aid in public presentations and bringing space science to the public. The work is part of the development of the software OpenSpace, which is the result of a collaboration between Linköping University, AMNH and the National Aeronautics and Space Administration (NASA) among others.
157

Anwendung des Systems Engineering zur Verbesserung des Betriebes von planetaren Missionen: Anwendung des Systems Engineering zur Verbesserung des Betriebes vonplanetaren Missionen

Liepack, Otfrid G. 24 November 2006 (has links)
Aufgrund des Mißerfolges der Mars Observer Mission 1992 und allgemeiner sinkender Raumfahrtetats, entwickelte NASA 1995 die „Faster Better Cheaper“ (FBC) Philosophie. Diese sah vor, daß planetare Missionen innerhalb eines kurzen Zeitraumes und mit begrenzten Budgets geplant, gebaut, getestet und gestartet werden sollten. Dabei sollten neue Technologien und neue Betriebsmethoden zum Einsatz kommen. Mögliche Fehlschläge durch unerprobte Instrumente oder Prozesse wurden dabei nicht ausgeschlossen. Der Mißerfolg der Mars-Missionen im Jahr 1999 und weiterer Projekte zwangen jedoch zu einem Umdenken der „Faster Better Cheaper“ Philosophie. Eine Vielzahl von Abhandlungen und Untersuchungen wurden daraufhin veröffentlicht, die Fehler der FBC Philosophie aufzeigten, ohne dabei jedoch auf mögliche Verbesserungen einzugehen. Das Ziel dieser Arbeit besteht in der Ermittlung effektiver Maßnahmen, so daß Ressourcen während des Lebenszyklus eines Projektes optimal eingesetzt werden können. Aus der Analyse der fehlgeschlagenen Missionen und einer Erläuterung der Funktionen verschiedener planetarer Missionskonzepte, werden mögliche Maßnahmen zur Verringerung der Kosten ermittelt. Die Effektivität dieser Maßnahmen wird anhand eines Bewertungskataloges im Rahmen einer Simulation zu verschiedenen Zeitpunkten einer Mission bestimmt. Es wird dabei eine Handlungshilfe erstellt, mit der ein Projektmanager die Verteilung von Ressourcen optimieren kann. Die Systemtechnik bietet hierzu eine Vielzahl von Analyse- und Simulationsmethoden, mit der die hier gemachten Angaben bewertet und überprüft werden können. / Due to the failure of the Mars Observer Mission in 1992 and decreasing budgets, NASA developed a new philosophy for the development, design and operations called „Faster Better Cheaper“ (FBC). New technologies and new management methods were deployed to reduce lift cycle costs. Possible mission failures were expected. After the losses of the Mars Missions in 1999 and other missions, NASA was forced to rethink its FBC approach. Numerous papers have been published in the meantime which identified the mistakes of the missions and of FBC, but none have identified potential improvements. The objective of this paper is the development of potential measurements for the design of the operations of unmanned space missions that should be applied during its life cycles. A new tool in form of an EXCEL spreadsheet will be developed based on historical missions, which can be used a program manager who can allocate resources in optimal way. Systems Engineering Techniques will be used in various ways to identify problems and to measure potential improvements.
158

Towards a Canfield Joint for Deep Space Optical Communication

Collins, Kristina V. 29 January 2019 (has links)
No description available.
159

Orbital Fueling Architectures Leveraging Commercial Launch Vehicles for More Affordable Human Exploration

Tiffin, Daniel Joseph 28 January 2020 (has links)
No description available.
160

Human Fatigue in Prolonged Mentally Demanding Work-Tasks: An Observational Study in the Field

Ahmed, Shaheen 17 August 2013 (has links)
Worker fatigue has been the focus of research for many years. However, there is limited research available on the evaluation and measurement of fatigue for prolonged mentally demanding activities. The objectives of the study are (1 )to evaluate fatigue for prolonged, mentally demanding work-tasks by considering task-dependent, task-independent and personal factors, (2) to identify effective subjective and objective fatigue measures, (3) to establish a relationship between time and factors that affect fatigue (4) to develop models to predict fatigue. A total of 16 participants, eight participants with western cultural backgrounds and eight participants with eastern cultural backgrounds, currently employed in mentally demanding work-tasks (e.g., programmers, computer simulation experts, etc.) completed the study protocols. Each participant was evaluated during normal working hours in their workplace for a 4-hour test session, with a 15-minute break provided after two hours. Fatigue was evaluated using subjective questionnaires (Borg Perceived Level of Fatigue Scale and the Swedish Occupational Fatigue Index (SOFI)); and objective measures (change in resting heart rate and salivary cortisol excretion). Workload was also assessed using the NASA-TLX. Fatigue and workload scales were collected every 30 minutes, cortisol at the start and finish of each 2-hour work block, and heart rate throughout the test session. Fatigue significantly increased over time (p-value <0.0001). All measures, except cortisol hormone, returned to near baseline level following the 15-minute break (p-value <0.0001). Ethnicity was found to have limited effects on fatigue development. Poor to moderate (Rho = 0.35 to 0.75) significant correlations were observed between the subjective and objective measures. Time and fatigue load (a factor that impacts fatigue development) significantly interact to explain fatigue represented by a hyperbolic relationship. Predictive models explained a maximum of 87% of the variation in the fatigue measures. As expected, fatigue develops over time, especially when considering other factors that can impact fatigue (e.g. hours slept, hours of work), providing further evidence of the complex nature of fatigue. As the 15-minute break was found to reduce all measures of fatigue, the development of appropriate rest breaks may mitigate some of the negative consequences of fatigue.

Page generated in 0.0263 seconds