Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 1988. / Title as it appeared in M.I.T. Graduate List, Sept. 1987: Calculations of helicopter blade loading using an axisymmetric vortex sheet and free wake method. / Bibliography: leaves 75-77. / by Kevin Huh. / M.S.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 2007. / This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections. / Vita. / Includes bibliographical references (p. 178-187). / Artificial gravity (AG) created by short-radius centrifugation is a promising countermeasure to the physiological de-conditioning that results from long-duration spaceflight. However, as on Earth, gravity alone does not ensure fitness. We will need to supplement passive exposure to AG with physical exercise to achieve a comprehensive countermeasure. Before AG exercise can be deemed safe and effective, we must understand how Coriolis accelerations and a gravity gradient affect our biomechanics and how centrifuge-based exercises differ from Earth-upright ones. Two experiments were designed to investigate the squat biomechanics while upright in the laboratory and while lying supine on a horizontal, clockwise-rotating short-radius centrifuge at speeds up to 30 revolutions per minute. Constant force springs provided additional resistive force up to 25% of body weight. Dependent measure included the three-dimensional position of the left and right knee, left and right foot reaction forces, and muscle activity. We investigated the Coriolis-induced mediolateral knee perturbations and the sensory-motor after-effects from a multiple repetition protocol. The upright and centrifuge biomechanics were compared for similarities and differences between them. In addition, a two-dimensional kinematic model was developed to predict foot reaction forces, Coriolis accelerations, and joint torques. / (cont.) Our results show that mediolateral knee travel during the AG squats was 1.0 to 2.0 centimeters greater than Earth-upright squats. Increasing the rotation rate or adding resistive force did not affect the results. The peak foot forces increased with rotation rate, but rarely exceeded 200% body weight. The ratio of left-to-right foot force during centrifugation was non-constant and approximately sinusoidal, suggesting a postural correction for the Coriolis accelerations. There was a qualitative difference in the foot force vs. knee angle profile between upright and centrifuge-supine because of the centripetal acceleration. Muscle activity, however, was qualitatively similar between the conditions. The kinematic model was used to evaluate the exercise safety and extend the results to larger-radius centrifuges. We conclude that centrifugation provides a unique and challenging environment for exercise and that a brief artificial gravity squat can be carried out safely. The results are extended to cycle ergometry, when possible, and recommendations are made for future AG squat protocols. Supported by NASA Grant NNJ04HD64G and the MIT-Italy Program Progetto Roberto Rocca. / by Kevin Ronald Duda. / Ph.D.

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 1991. / On t.p., "[infinity]" appears as the infinity sign in subscript. / Includes bibliographical references (leaves 119-120). / by Om Prakash, II. / M.S.

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 1995. / Includes bibliographical references. / by Timothy S. Glenn. / 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. 223-227). / As demand for air travel increases over the years and many busy airports operate close to their capacity limits, congestion at some airports on any given day can quickly spread throughout the National Aviation System (NAS). It is therefore increasingly important to study the operation of large networks of airports as a group and to understand better the interactions among them under a wide range of conditions. This thesis develops a fundamental tool for this purpose, enhances it with several capabilities designed to address issues of particular interest, and presents some early insights and observations on the system-wide impacts of various scenarios of network-wide scope. We first describe an analytical queuing and network decomposition model for the study of delays and delay propagation in a large network of airports. The Airport Network Delays (AND) model aims to bridge the gap in the existing modeling tools between micro-simulations that track aircraft itineraries, but require extensive resources and computational effort, and macroscopic models that are simple to use, but typically lack aircraft itinerary tracking capabilities and credible queuing models of airport congestion. AND operates by iterating between its two main components: a queuing engine (QE), which is a stochastic and dynamic queuing model that treats each airport in the network as a M(t)/Ek(t)/1 queuing system and is used to compute delays at individual airports and a delay propagation algorithm (DPA) that updates flight schedules and demand rates at all the airports in the model in response to the local delays computed by the QE. We apply AND to two networks, one consisting of the 34 busiest airports in the United States and the other of the 19 busiest in Europe. As part of the development of AND, we perform a statistical analysis of the minimum ground turn-around times of aircraft, one of the fundamental variables that determine delay propagation. In addition, we show that the QE, with proper calibration, can model very accurately the airport departure process, predicting delays at two major US airports within 10% of observed values. We also validate the AND model on a network-wide scale against field data reported by the FAA. Finally, we present insights into the complex interactions through which delays propagate through a network of airports and the often-counterintuitive consequences. In the third part of the thesis, we present two important extensions of the AND model designed to expand its usability and applicability. First, in order to provide a more accurate representation of NAS operations, we develop an algorithm that replicates quite accurately the execution of Ground Delay Programs (GDPs). The algorithm operates consistently with the rules of the Collaborative Decision-Making (CDM) process under which GDPs are currently conducted in the United States. The second extension is the implementation in AND of a deterministic queuing engine (D(t)/D(t)/1) which can be used as an alternative to the original stochastic QE. This deterministic model can be used to study delay-related performance in a future system that operates at a higher level of predictability than the current one, as the one envisioned by FAA in the Next Generation Air Transportation System. In the final part of the thesis we describe a Mixed Integer optimization model for studying the impact of introducing slot controls at busy airports. The model generates new flight schedules at airports by reducing the number of available slots, while respecting all existing aircraft itineraries and preserving all passenger connections. We test the model at Newark Airport (EWR) and conclude that, with a small schedule displacement (less than 30 minutes for any flight during the day), it is possible to obtain a feasible schedule that obeys slot limits that are as low as the IFR capacity of the airport. We test the new schedule in AND and find that the local delay savings that would result from "slot-controlling" EWR in this way are of the order of 10% for arrivals and of 50% for departures, while we may also expect a reduction of 23% in propagated delays to the rest of the US network of airports. / by Nikolaos Pyrgiotis. / Ph.D.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 2013. / This electronic version was submitted and approved by the author's academic department as part of an electronic thesis pilot project. The certified thesis is available in the Institute Archives and Special Collections. / Cataloged from department-submitted PDF version of thesis. / Includes bibliographical references (p. 181-189). / There are important tradeoffs that need to be considered for the design and operation of aerospace systems. In addition to tradeoffs, there may also be multiple stakeholders of interest to the system and each may have different preferences as to the balance amongst the tradeoffs under consideration. A tradeoff hyperspace is created when there are three or more tradeoff dimensions and this increases the challenge associated with resolving the hyperspace in order to determine the best design and operation of a system. The corresponding objectives of this research are to develop a framework to analyze tradeoff hyperspaces and to account for the preferences of multiple stakeholders in this framework. The framework developed in this research is called the Tradeoff Analysis Framework and its applicability was evaluated through analyzing three different case studies in the aerospace domain, each progressively more complex in terms of applying the framework and exploring the impact of certain types or change, or innovation in the system of interest. The first case study analyzed the impact of changing aircraft cruise operations and one facet of the case study explored the impact of imposing a hypothetical tax on aircraftproduced contrails. From this study it was determined that airlines will change their behavior (i.e., their perceived value-optimal cruise trajectory) in response to a tax placed on producing contrails where, the higher the tax, the less contrails they choose to produce. The second case study explored the impact of changes in aircraft approach procedures into Boston-Logan airport. In this study, there were multiple stakeholders, each with different preferences as to the balance amongst the performance and environmental tradeoffs considered. A key result from this study was that competing stakeholder preferences could be partially resolved, which led to the design new approach procedures that were beneficial to all stakeholders. The third and last case study examined the tradeoffs associated with using fractionated spacecraft for remote sensing space missions. Here, the current paradigm is monolithic spacecraft and it was found that despite fractionated spacecraft demonstrating more value-robustness than a comparable monolith, they fail to stay value-competitive to monoliths in terms of absolute value delivered. In particular, this occurs because presently the enabling technologies required for fractionated spacecraft are not yet mature and reliable enough at the performance levels needed for them to become viable alternatives to monoliths. Along with insights gained in the case studies about the systems of interest, through applying the Tradeoff Analysis Framework insights were gained with respect to implementing the framework. These insights form the methodological contributions of this research since they offer opportunities to learn about the breadth of potential framework applicability and areas for subsequent improvements in the framework for future use. / by Michael Gregory O'Neill. / Ph.D.

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 1994. / Includes bibliographical references (p. 153-155). / by Robert B. Brown. / M.S.

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 1992. / Includes bibliographical references (leaves 183-186). / by Laura Ann Kozel. / M.S.

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 1994. / Includes bibliographical references (p. 99-100). / by Michael Patrick Fikes. / M.S.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 2003. / Includes bibliographical references (p. 169-172). / This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections. / Modern engineering practice for designing physical products requires the creation of a CAD model of the design for documentation and manufacturing. As the design evolves from concept through to production, it is analyzed a number of times, in some cases using general parameters and in others requiring fine details of the product's form. The setup of each analysis is typically disjoint from the previous steps, inhibiting design changes and optimization. This thesis addresses these bottlenecks by proposing a methodology to use the CAD model of the system as the central element. The model is created at the earliest possible stage of the process following a strict synthesis procedure; it then forms a common base for all of the follow-on analyses and development. Computational tools are developed to aid in using the geometric and parametric information in the CAD model to setup simulations, as well as to dynamically drive the CAD model itself for design studies and optimization. The methods and tools are then applied to the design of a wind turbine for power production. Using a common CAD model, various analysis codes and optimization algorithms are applied to the design of the system, to lower the cost of delivered energy. Multidisciplinary aspects of wind turbine design including aerodynamics, structures, and economics are presented together with the employed modeling techniques. The demonstrated improvements achieved over the baseline design lend credence to the methodology, and demonstrate its effectiveness in enhancing the systems performance. The insights gleaned from the present work intimate promising directions for continued development both at the level of software tools and also effective methods for approaching multi-disciplinary design. / by Curran A. Crawford. / S.M.