Browsing by Subject "Systems engineering"
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Item An integration of systems, simulation, and EDP in the design of an information model(Texas Tech University, 1967-08) Lokey, Kenneth RayNot availableItem The application of systems engineering to a Space-based Solar Power Technology Demonstration Mission(2012-05) Chemouni Bach, Julien; Fowler, Wallace T.; Guerra, Lisa A.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.Item Computer implementation of term expansion in fault analysis.(Texas Tech University, 1975-08) Tsui, Ying-LongNot availableItem Design with Uncertain Technology Evolution(2012-10-19) Arendt, Jonathan LeeDesign is an uncertain human activity involving decisions with uncertain outcomes. Sources of uncertainty in product design include uncertainty in modeling methods, market preferences, and performance levels of subsystem technologies, among many others. The performance of a technology evolves over time exhibiting improving performance as research and development efforts continue. As the performance of a technology in the future is uncertain, quantifying the evolution of these technologies poses a challenge in making design decisions. Designing systems involving evolving technologies is a poorly understood problem. The objective of this research is to create a computational method allowing designers to make decisions encompassing the evolution of technology. Techniques for modeling evolution of a technology that has multiple performance attributes are developed. An S-curve technology evolution model is used. The performance of a technology develops slowly at first, quickly during heavy R&D effort, and slowly again as the performance approaches its limits. Pareto frontiers represent the set of optimal solutions that the decision maker can select from. As the performance of a technology develops, the Pareto frontier shifts to a new location. The assumed S-curve form of technology development allows the designer to apply the uncertainty of technology development directly to the S-curve evolution model rather than applying the uncertainty to the performance, giving a more focused application of uncertainty in the problem. Monte Carlo simulations are used to the propagate uncertainty through the decision. The decision-making methods give designers greater insight when making long-term decisions regarding evolving technologies. The scenario of an automotive manufacturing firm entering the electric vehicle market deciding which battery technology to include in their new line of electric cars is used to demonstrate the decision-making method. Another scenario of a wind turbine energy company deciding which technology to invest in demonstrates a more sophisticated technology evolution modeling technique and the decision making under uncertainty method.Item Development of consistent nonlinear models of flexible body systems(Texas Tech University, 1998-12) Eskridge, Steven ENot availableItem The development of replicated optical integral field spectrographs and their application to the study of Lyman-alpha emission at moderate redshifts(2015-08) Chonis, Taylor Steven; Hill, Gary J.; Finkelstein, Steven L; Gebhardt, Karl; Greene, Jenny E; Jaffe, Daniel TIn the upcoming era of extremely large ground-based astronomical telescopes, the design of wide-field spectroscopic survey instrumentation has become increasingly complex due to the linear growth of instrument pupil size with telescope diameter for a constant spectral resolving power. The upcoming Visible Integral field Replicable Unit Spectrograph (VIRUS), a baseline array of 150 copies of a simple integral field spectrograph that will be fed by 33,600 optical fibers on the upgraded Hobby-Eberly Telescope (HET) at McDonald Observatory, represents one of the first uses of large-scale replication to break the relationship between instrument pupil size and telescope diameter. By dividing the telescope's field of view between a large number of smaller and more manageable instruments, the total information grasp of a traditional monolithic survey spectrograph can be achieved at a fraction of the cost and engineering complexity. To highlight the power of this method, VIRUS will execute the HET Dark Energy Experiment (HETDEX) and survey ~420 square degrees of sky to an emission line flux limit of ~1e-17 erg/s/cm^2 to detect ~1e6 Lyman-alpha emitting galaxies (LAEs) as probes of large-scale structure at redshifts of 1.9Item An evaluation of cost in government aircraft acquisition programs(2011-08) Reynolds, Robert Paul; McCann, Robert Bruce, 1948-; Nichols, Steven Parks, 1950-Aircraft system development has been steadily increasing in cost since the inception of human flight. Several factors have influenced this including economics, increasing complexity and increased customer expectations and requirements. In addition, the contractors which produce these systems have almost consistently been unable to complete them within the originally contracted budget and schedule. The factors which influence cost increase have been studied extensively by industry, government and private organizations and a study of those findings will be conducted in the following work with the intention of determining the factors which are primarily responsible for cost increase in aircraft acquisition programs. Following the discussion of data, recommendations for reducing cost will made with the goal of identifying the methods with which systems engineering can be used to improve the process at the system and program level. The intent will be to show how improved techniques for managing programs, meeting customer requirements and improving cost estimates can be implemented to manage cost growth. The ultimate goal of this study is to show that program risk can and should be managed more effectively and that high technology programs can be executed if they are properly managed.Item Important systems engineering analysis tools : failure mode and effects analysis and hazard analysis(2010-12) Moore, Alicia Louise Leonard; Ambler, Tony; McCann, Robert B.The goal of every program or project manager is to have a safe reliable product and to have an understanding of the residual risk of operating that product. Two very important systems engineering analysis tools to achieve those objectives are Hazard Analysis and Failure Modes and Effects Analysis. Sometimes seen strictly as Safety and Reliability tasks, these analyses are key to a successful program or project and require input from all stakeholders. When viewed in the Systems Engineering process, Safety and Reliability are truly specialty disciplines within Systems Engineering. Hazard Analysis is used to improve system safety while Failure Modes and Effects Analysis is used to identify ways to increase product reliability; both analyses are required to improve systems design and fully capture the risk for a system or program. Depending on how the analyses are scoped, there could be a perception of overlap and duplication of effort. This paper will present a systems engineering approach to show the need and benefits for performing both types of analyses. Both analysis processes are required to ensure that all possible hazardous conditions and failure modes have been identified and addressed to minimize overall risk to the program/project and to ensure a safe and reliable system.Item Object-oriented modeling for the integrated process planning and production scheduling system(Texas Tech University, 1998-05) Zhang, DaguangThis research explores an object-oriented generic model for integrated process planning and production scheduling. The research employs the most advanced objectoriented modeling technique and tools to implement a hierarchical-interactive process planning approach which integrates the process planning and production scheduling functions through a stepwise integration advancement. The integration of process planning and production scheduling is a comprehensive, controversial, and complicated topic to both academia and industry. Both process planning and production scheduling play important roles in manufacturing systems. Traditionally, these two functions are separated and have their own planning goals, constraints, and methodologies. The integration of these two functions has been driven by the fact that many process plans cannot be executed on the shop floor because the production constraints are not considered during the process planning. However, the implementation of the integrated planning remains an enigmatic task because of its complexity. While many studies have been conducted, more efforts are yet to be invoked. In this research, the integration of process planning and production scheduling is approached by a Hierarchical-Interactive Process Planning (HIPP) architecture, which has been modeled in the object-oriented paradigm. The HIPP includes three levels interactions between process planning and production functions. The functional and data gaps in the existing separated planning are bridged through object-oriented systems models.Item Optimal availability allocation in a multi-stage system(Texas Tech University, 1969-08) Wilkinson, Robert ENot availableItem Optimal redundancy and availability allocation in multi-stage systems(Texas Tech University, 1970-08) Hirmas, Juan PNot availableItem Refinement of the requirement definition concept in system development(Texas Tech University, 1998-12) White, Michelle MayRequirement definition is an integral part of system development and is a factor that contributes to the success of system development. Throughout the literature there are documented problems and issues with respect to defining requirements for system development. There is evidence to indicate that requirement definition is often not performed well, not communicated effectively, and is lacking measures. A comprehensive view of requirement definition is missing throughout the literature. The objective of the research was to refine the requirement definition concept during system development by developing a comprehensive representation of the concept that is organized, coherent, unified and measurable. The researcher surveyed literature for existing information regarding requirement definition, such as requirement processes, models, issues, case studies, and measures. The researcher generated methods to synthesize and refine this information. Since a consensus or comprehensive requirement definition representation was not found in the literature, the researcher developed methods to determine the areas of requirement definition. Methods were developed by the researcher to determine the primary functions performed in each requirement definition area and the area interactions. The researcher developed measures for each area of requirement definition and these were used by the researcher to generate a requirement definition assessment audit to compare a project's requirement definition effort to the comprehensive requirement definition representation generated in this research. The assessment audit provides feedback to a project regarding strengths and weaknesses of the requirement definition effort.Item A software tool suite for small satellite risk management(2015-05) Gamble, Katharine Brumbaugh; Fowler, Wallace T.Risk management plans improve the likelihood of mission success by identifying potential failures early and planning mitigation methods to circumvent any issues. However, in the aerospace industry to date, risk management plans have typically only been used for larger and more expensive satellites, and have rarely been applied to satellites in the shape of 10 x 10 x 10 centimeter cubes, called CubeSats. Furthermore, existing risk management plans typically require experienced personnel and significant time to run the analysis. The purpose of this research was to develop two risk management software tools, the CubeSat Risk Analysis tool and the CubeSat Decision Advisor tool, which could be used by anyone with any level of experience. Moreover, the tools simply require the user to enter their mission-specific data; the software tools calculate the required analysis. The CubeSat Risk Analysis tool was developed for the purpose of reducing the subjectivity associated with estimating the likelihood and consequence of spacecraft mission risks. The tool estimates mission risk in terms of input characteristics, such as satellite form factor, mass, and development cycle. Using a historical database of small satellite missions, which was gathered in the course of this research, the software determines the mission risk root causes which are of the highest concern for the given mission. The CubeSat Decision Advisor tool uses components of decision theory such as decision trees, multi-attribute utility theory, and utility elicitation methods to determine the expected utility of a mitigation technique alternative. Based on the user’s value preference system, assessment of success probabilities, and resources required for a given mitigation technique, the tool suggests the course of action which will normatively yield the most value for the cost, personnel, and time resources required. The goals of this research were met in the development of two easily-accessible and free risk management software tools to assist in university satellite mission development. But more importantly, these tools will reach beyond the academic setting and allow small satellites to continue to evolve as a platform to accomplish educational, scientific, and military objectives.Item Systems engineering processes for a student-based design laboratory(2009-12) Garner, Michael Dax; Bishop, Robert H., 1957-; Guerra, Lisa A.A student-based university environment for engineering design and development is much different from a product development environment within the aerospace industry. Therefore, a different approach to systems engineering should be considered. By its very nature, a university product development laboratory thrives on creativity and rejects bureaucracy. Experience shows that continuity and discipline within a project is crucial for success. The practice of systems engineering enables technical project discipline. Systems engineering is the art and science of developing an operable system that meets requirements within imposed constraints. The purpose of this thesis is to describe the systems engineering processes and techniques necessary for a student-based project, and explicitly show how to implement these processes. Although attempts have been made to utilize a few systems engineering techniques in past projects, many students did not properly and consistently apply those techniques to the technical design work. The goal of the thesis is to tailor the NASA systems engineering processes to a student-based design laboratory environment and to apply the methodologies to the mission design of Paradox. The Picosatellite for Autonomous Rendezvous and Docking on-Orbit eXperiment, or Paradox, is the second of four missions to demonstrate autonomous rendezvous and docking with a picosatellite-class satellite. A strong technical contribution highlighted within the thesis involves developing an open architecture rendezvous targeting algorithm for the Paradox mission in the face of large mission architecture uncertainties. The robust targeting algorithm builds from previous work utilizing an optimizer based on the Clohessey-Wiltshire equations and an iterative Lambert targeter. The contribution extends the rendezvous transfer times by including a multi-revolution Lambert targeter. The rendezvous algorithm will perform successfully given any launch vehicle and target spacecraft vehicle supporting the notion of an open architecture to satisfy the mission. The development of the algorithm is embedded within the context of the systems engineering processes to clearly showcase the intimate connection between systems engineering processes and the technical engineering design of a mission.