Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 2004. / Vita. / Includes bibliographical references (p. 66). / Computer aided design has allowed many design decisions to be made before hardware is built through "virtual" prototypes: computer simulations of an engineering design. To produce robust systems noise factors must also be considered (robust design), and should they should be considered as early as possible to reduce the impact of late design changes. Robust design on the computer requires a method to analyze the effects of uncertainty. Unfortunately, the most commonly used computer uncertainty analysis technique (Monte Carlo Simulation) requires thousands more simulation runs than needed if noises are ignored. For complex simulations such as Computational Fluid Dynamics, such a drastic increase in the time required to evaluate an engineering design may be probative early in the design process. Several uncertainty analysis techniques have been developed to decrease the number of simulation runs required, but none have supplanted Monte Carlo. Gaussian Quadrature (GQ) is presented here as a new option with significant benefits for many types of engineering problems. Advantages of GQ include: as few as 2*(number of noise factors) simulation runs required to estimate performance mean and variance, errors dependent only on the ability to approximate performance using polynomials for each noise factor, and the ability to estimate gradients without further simulation rims for use in computer aided optimization of mean or variance. The mathematically basis for GQ is discussed along with case studies demonstrating its utility. / by Geoffrey Scott Reber. / S.M.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 2001. / Includes bibliographical references (p. 79-83). / by Adam Theodore Hendriks. / S.M.

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 1974. / Bibliography: p. 87-88. / M.S.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 2012. / Cataloged from PDF version of thesis. / Includes bibliographical references (p. 399-412). / System architecting is concerned with exploring the tradespace of early, high-level, system design decisions with a holistic, value-centric view. In the last few years, several tools and methods have been developed to support the system architecting process, focusing on the representation of an architecture as a set of interrelated decisions. These tools are best suited for applications that focus on breadth - i.e., enumerating a large and representative part of the architectural tradespace -as opposed to depth - modeling fidelity. However, some problems in system architecting require good modeling depth in order to provide useful results. In some cases, a very large body of expert knowledge is required. Current tools are not designed to handle such large bodies of knowledge because they lack scalability and traceability. As the size of the knowledge base increases, it becomes harder: a) to modify existing knowledge or add new knowledge; b) to trace the results of the tool to the model assumptions or knowledge base. This thesis proposes a holistic framework for architecture tradespace exploration of large complex systems that require a large body of expert knowledge. It physically separates the different bodies of knowledge required to solve a system architecting problem (i.e., knowledge about the domain, knowledge about the class of optimization or search problem, knowledge about the particular instance of problem) by using a rule-based expert system. It provides a generic population-based heuristic algorithm for search, which can be augmented with rules that encode knowledge about the domain, or about the optimization problem or class of problems. It identifies five major classes of system architecting problems from the perspective of optimization and search, and provides rules to enumerate architectures and search through the architectural tradespace of each class. A methodology is also defined to assess the value of an architecture using a rule-based approach. This methodology is based on a decomposition of stakeholder needs into requirements and a systematic comparison between system requirements and system capabilities using the rules engine. The framework is applied to the domain of Earth observing satellite systems (EOSS). Three EOSS are studied in depth: the NASA Earth Observing System, the NRC Earth Science Decadal Survey, and the Iridium GEOscan program. The ability of the framework to produce useful results is shown, and specific insights and recommendations are drawn. / by Daniel Selva Valero. / Ph.D.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 2008. / Includes bibliographical references (p. 117-118). / This thesis presents an approach to applying Systems Architecture methods to the development of large, complex, commercial systems, particularly offshore oil and gas productions systems. The aim of this research was to assist BP in the development of concepts for a multi-billion dollar oil production system, particularly in the unprecedented deep water arctic locations prone to seismic activity, as well as in existing fields that must be extended. The thesis demonstrates that these systems can be decomposed and analyzed using rigorous, methodical system architecture thinking that archives and represents tacit knowledge in several graphical frameworks. The thesis breaks the architecture of oil and gas production systems into two problems. The first problem is the architecture of one facility and one reservoir; a classic problem of assigning function to form. The second problem is the architecture of multiple facilities and multiple reservoirs; a classic problem of connection and routing. For the first problem, the production process is decomposed using Object Process Methodology (OPM). The decompositions provide a methodology to capture industry knowledge that is not always explicitly stated and provides a framework to explore the entire architectural design space. The thesis then describes how these decompositions of general and specific oil systems can be used to develop software models, using the meta-language tool OPN (Object Process Network), that successfully generate thousands of architecture concepts. This set of feasible architectures can be prioritized and better understood using metrics in an effort to down-select to a handful of preferred concepts to be carried forward for more detailed study and eventual development. / (cont.) The approach to the second problem demonstrates that even a modest set of facilities and reservoirs have a huge number of connection possibilities. This space of connection possibilities is large and daunting, and typically is not fully explored. To solve the second problem the thesis presents two models that generate all the possible connection schemes between elements in a system, in this case oil facilities and reservoirs. It is then demonstrated that these possibilities can be prioritized through the use of metrics. The thesis presents a method that can identify new concepts, highlight preferred sets of concepts, and underline patterns common to those concepts. This method increases the architects' overall knowledge and understanding of the entire space of possibilities, and ensures that all options are considered in the development of complex systems. / by James Keller. / S.M.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 2010. / Cataloged from PDF version of thesis. / Includes bibliographical references (p. 69-74). / Composites have seen an increasing role in aerospace structures that demand lightweight, strong, and stiff materials. Composites are attractive structural materials with outstanding mechanical and physical properties, as well as directional fabrication control and tailorability, though these advantages come with increased complexity and challenging failure modes. Matrix-rich regions at ply interfaces especially are susceptible to damage and matrix cracking, leading to delamination and a reduction of mechanical properties. Several manufacturing solutions such as stitching, z-pinning, and braiding have been developed by the aerospace industry to provide through-thickness reinforcement and improve interlaminar properties, though these improvements come with concomitant reductions in important in-plane properties. This thesis describes the design, manufacturing, and testing of woven composites with aligned carbon nanotubes (CNTs) integrated into the bulk composite, focusing here particularly on interlaminar reinforcement at ply interfaces. Implementing aligned CNTs takes advantage of their scale and superior specific stiffness and strength, with in-plane properties maintained while interlaminar properties are enhanced by the CNTs bridging across matrix-rich interfaces. Significant improvement in Mode I fracture toughness is observed experimentally with over 60% increase in both initiation and steady-state Mode I fracture toughnesses (steady-state toughness improves from 2.1 to 3.7 kJ/m² ). This enhancement is attributed to CNT crackbridging and pullout, in agreement with a first-order model, confirming the viability of CNTs to improve composite interlaminar properties. Future work to follow this thesis will focus on development of a vacuum-assisted infusion manufacturing process implementation of the 'fuzzy'-fiber reinforced nano-engineered composite architecture with alternate fiber and polymer systems, and exploring multifunctional applications of these materials. / by Sunny S. Wicks. / S.M.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 2012. / Cataloged from PDF version of thesis. / Includes bibliographical references (p. 110-112). / Performance Based Navigation (PBN) is a key element of the Federal Aviation Administration's (FAA) NextGen Program. In order to increase National Airspace System (NAS) capacity and efficiency, PBN routes and procedures are being developed, including Area Navigation (RNAV) and Required Navigation Performance (RNP) procedures. RNAV enables aircraft to fly directly from point-to-point on any desired flight path using groundor spaced-based navigation aids. RNP is RNAV with the addition of onboard monitoring and alerting capability. Both RNAV and RNP procedures allow aircraft to fly accurate routes without relying on ground-based navigation aids. RNAV and RNP procedures facilitate more efficient design of airspace and procedures, offering significant safety improvements and flexibility to negotiate terrain, as well as improving airspace capacity and operational efficiency. The initial implementation of RNAV and RNAV (RNP) procedures has raised several human factors issues. RNAV (RNP) Instrument Approach Procedures (IAP) and RNAV Standard Instrument Departures (SID) and Standard Terminal Arrivals (STARs) often have more waypoints, altitude constraints and other elements than conventional procedures, resulting in charts being cartographically complex. Thus, a chart review was conducted to objectively understand the procedure elements that contributed to increased information density and high levels of visual clutter. A total of sixty-three approach, fifty-two departure, and fifty-four arrival procedures were analyzed. Primary findings were that the factors associated with high levels of visual clutter included having multiple flight paths per page for approach and departure procedures, and having complex altitude constraints for arrival procedures. Multiple waypoints per path was also a factor for both arrivals and approaches. In addition, having RF legs were additional factor contributing to visual clutter for approach procedures. One method to mitigate the increased information density and visual clutter on the RNAV and RNP procedure depiction is to reduce the number of flight paths shown on a single page by separating the depicted paths to multiple pages. However, there are a number of drawbacks to this clutter mitigation technique. Example drawbacks include having more paper to carry in the flight deck and more time spent searching for the correct page within a set of separated pages. An experiment was conducted to determine the effect of reducing the number of paths depicted on single-page "Modified" charts. FAA AeroNav Products and Jeppesen created versions of the Modified chart in their standard cartographical conventions. The experiment was conducted to evaluate whether these Modified charts would impact information retrieval time and accuracy compared with the "Current" charts being used now. Current FAA AeroNav Products and Jeppesen charts were used as the baseline condition. Six procedures were studied, including three RNAV departure procedures from Dallas/Fort Worth, Las Vegas, and Salt Lake City airports, and three RNAV (RNP) approach procedures from Boise, Bozeman, and Palm Springs airports. During the experiment, pilots were shown the same procedure in Current and Modified chart formats. All charts were displayed electronically on a high-resolution computer monitor. Pilots were asked information retrieval questions associated with each chart. Pilot response time and accuracy with which pilots answered the information retrieval questions were recorded. Pilots completed the task in two blocks, one for approaches and one for departures. The Current and Modified charts within each block were presented in random order, and the order of the two blocks was counterbalanced. Each block began with six practice questions. Each session took approximately one hour to complete. Data were collected from 28 commercial airline pilots and 19 corporate pilots with average flight experience of 11,484 hours. Fourteen pilots used FAA AeroNav charts, and 33 pilots used Jeppesen charts. Pilots were found to answer questions faster using Modified charts than Current charts. This effect was statistically significant with a p-value less than 0.01. For approach procedures, the mean response time for Current charts was 16.9 seconds, compared with 10.6 seconds for Modified charts. For departure procedures, the mean response time for Current charts was 16.2 seconds, compared with 13.2 seconds for Modified charts. Response times were also significantly faster for Modified charts than for Current charts when analyzed for each airport, chart manufacturer (Jeppesen and FAA AeroNav Products), and pilot type (Corporate and Airline). Overall question response accuracy for all 47 participants was 99.5%. There were no statistically significant differences found for the response accuracy between Modified and Current chart use. / by Abhizna Butchibabu. / S.M.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 2001. / Includes bibliographical references (p. 175-179). / by Olivier Mongrard. / S.M.

Thesis: S.M., Massachusetts Institute of Technology, Department of Aeronautics and Astronautics, 2017. / Cataloged from PDF version of thesis. / Includes bibliographical references (pages 211-214). / Satellites at geosynchronous orbital altitudes are highly valuable for national defense, but are also difficult to access and monitor. Uncrewed inspection spacecraft could supervise various essential defense platforms and deter covert rendezvous by adversaries with malicious intent. 'Neighborhood watch' satellites tasked with this situational awareness mission should be designed and operated in such a way as to maximize their lifespan and efficacy. Motivated by this requirement, this thesis explores the prolonged medium- to close-range spacecraft proximity operations problem from the perspective of continuous optimal trajectory control. A numerical optimization framework is presented for developing and analyzing fuel-, energy-, and time-optimal trajectories with multiple phases using Gauss pseudospectral collocation software. Emphasis is placed on energy efficiency during inspection, for which accurate dynamical models play a critical role in formationkeeping fuel consumption. Various scenarios are analyzed for minimum-energy solutions, such as tactical phasing and insertion into periodic trajectories, avoidance of 'no-fly' zones, inclusion of coupling attitude dynamics, and operations with highly-eccentric targets. This thesis focuses primarily on proximity operations carried out in geosynchronous orbital regimes and neglects orbit perturbations, instead determining the pure cost of linearizing Keplerian gravity using the Hill-Clohessy-Wiltshire model. Error in relative position, angular rate of circumnavigation, and fuel use to enforce linearized periodic trajectories are characterized. It was determined that proximity operations utilizing low-thrust high-specific-impulse solar electric propulsion are well-suited to minimum-energy trajectory optimization with this method. While the contributed analysis tool is not suitable for on-board optimal trajectory generation, it provides a framework to perform useful pre-mission analyses. / by Zachary K. Funke. / S.M.

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 1988. / Includes bibliographical references. / by Dana Rae Lindquist. / M.S.