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. / Includes bibliographical references (p. 231-239). / Electric thrusters are being developed for in-space propulsion needs of spacecraft as their higher specific impulse enables a significant reduction in the required propellant mass and allows longer duration missions. Over the last few decades many different electric propulsion concepts have been proposed and studied. In studying the electric thrusters, in order to improve the thruster performance as well as to understand the underlying physics of thruster's operation, various diagnostics methods were employed. As one unique method, emission spectroscopy provides a non-invasive, fast and economical diagnostic allowing also the ability to access hard to reach locations. In this study, emission spectroscopy is employed as a means to determine the trends in thruster operations as well as diagnosing the plasma parameters. This study presents the spectral measurement results of three different electric thrusters and plasma sources. First, the BHT-200 Hall thruster emission spectra measurements are presented for varying discharge voltage and for various regions of observation. / (cont.) Second, spectral measurements of a TAL type laboratory mini-Hall thruster, MHT-9, were presented. Third, radiation emission measurements of an experimental Helicon plasma source being studied to assess the possibility of using Helicon discharge as a propulsive system are presented and the trends are discussed. Two collisional-radiative (C-R) models are developed for Argon and Xenon plasmas to analyze the experimental spectra. In the C-R models, electron induced excitation, deexcitation and ionization collisions, and spontaneous radiative de-excitation transitions are simulated for neutral and singly charged ion species. The models are validated against measured spectra obtained using different experimental setups. The BHT-200 Hall thruster has insulator ceramic annular walls made of Boron-Nitride (BN). Erosion of ceramic walls is one of the major life limiting factors for Hall thrusters. Emission spectroscopy is used as a means to determine the trends in the thruster wall erosion rate by measuring the radiation emission of the Boron neutral 249.68nm and 249.77nm lines. Discussion about the spectral measurements and relevant analysis are presented. / by Murat Çelik. / Ph.D.

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 1994. / Includes bibliographical references (p. 159-162). / by Brett P. Masters. / M.S.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 2009. / Cataloged from PDF version of thesis. / Includes bibliographical references (p. 99-100). / This thesis presents a path planning and control strategy that enables an unmanned non-holonomic vehicle to intercept a fast moving object. The path planning is performed under model uncertainty, with respect to the vehicle's maneuverability, as well as uncertainty in the estimation of the object's future trajectory and position. This problem involves the tracking of the dynamic object in a cluttered environment and the accurate estimation of its future position in the presence of noisy measurements. The ground vehicle (interceptor) is required to intercept the dynamic object at a predicted (catch) location in a finite amount of time. This time restriction presents quite a challenge given the inherent limitation in the vehicle's steering and maneuverability. The solution strategy is divided into three sub-problems: 1) prediction, 2) path planning and 3) control. The prediction of the parameters that describe the dynamic's object in space is accomplished via Kalman Filtering which, in conjunction with an impact predictor, provide the waypoints needed to construct a reference path that will place the interceptor on a collision course with the dynamic object (target.) A pure pursuit algorithm was used to steer the interceptor along a reference trajectory, which was designed to make the vehicle engage the dynamic object on a near tail-on aspect. In the endgame, the pure pursuit algorithm was modified to ensure arrival to the catch point while a position controller was added to ensure timely arrival to the predicted catch location. The problem statement was then augmented to include obstacle avoidance. / (cont.) The dynamic object was required to navigate around fixed obstacles in order to catch the dynamic object. Results will show that the proposed strategy performed very well in the absence of obstacles and was well suited to handle the maneuverability constraints of the non-holonomic vehicle. Results also will show that, with minor modifications to the path planner, the interceptor successfully managed to avoid obstacles and catch the dynamic object although at a slightly lower success rate. The proposed solution was first demonstrated in simulation and then tested using MIT's RAVEN testbed. / by Sergio A. Cafarelli. / S.M.

Massachusetts Institute of Technology. Dept. of Aeronautics and Astronautics. Thesis. 1970. M.S. / MICROFICHE COPY ALSO AVAILABLE IN AERONAUTICS LIBRARY. / Bibliography: p. 98-100. / M.S.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 2001. / Includes bibliographical references (p. 161-163). / Airline scheduling is a daunting task. Much time and resources are spent by airlines developing a schedule that meets expectations of profitability and competitiveness. Most of the time, however, the reliability aspect has a minor, if any, role in such a process. In reality disruption of the schedule occurs due to unforeseen events such as weather conditions, traffic congestion, and mechanical problems. The outcomes of these events are cancellations and delays. The impact that these disruptions have on airline operations is not only the increased cost for system maintenance and recovery, but also the loss of profitability and the perception of poor and unreliable service for the flying customer. In this thesis we present an analysis of the schedule design process, highlight the drawbacks of the current proceedings and outline of new and more flexible framework for schedule design. We define a reliability measure, the Option Value, and a way of comparing flights based on the reliability they are providing, via the Option Disruption Value. The idea of reliability is based on the concept of flight performance: a flight is more reliable if it is able to match or outperform the on-time performance of the flights that leaves its origin station and arrives at its final destination at or near its arrival and departure times. Based on these two measurements, we quantify the robustness and coverage of a sample schedule. Alternative passenger ratings are defined based on the concept of alternative itineraries (Coverage) and alternative independent itineraries (Robustness) that connect two locations. These are the Flight Options and the Flight Protection Options, respectively. Fifteen methods to modify flight schedule are proposed. One method, Reduce/increase Flight Slack Time (R/IFTS) was evaluated. Results indicate that R/IFTS was effective in increasing reliability in 70% of the flight considered, but that other methods need to be employed if reliability is to be increased further. / by Massimo Morin. / S.M.

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 1996. / Includes bibliographical references (p. 137-139). / by Michelle Vivian Bakkila. / M.S.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 2012. / Cataloged from PDF version of thesis. / Includes bibliographical references (p. 153-157). / Although a great deal of separate work exists on the development of spacecraft actuators and control algorithm design, less work exists which examines the connections between the selection of specific actuator types and placements, how this affects control algorithm design, and how these combined factors affect the overall vehicle performance of a lunar lander. This thesis attempts to address these issues by combining a functionality-oriented approach to actuator type/placement with a controls-oriented approach to algorithm design and performance analysis. Three example control system architectures are examined for a generic autonomous 350kg lunar lander during the terminal descent flight phase. Results indicate that stability and control can be achieved using a wide variety of actuator types/placements and algorithms given that a set of 'common sense' subsystem functionality and robustness metrics are met; however, algorithm development was often heavily influenced/restricted by actuator system capabilities. It is therefore recommended that future designers of lunar lander vehicles consider the impact of their control system architectures from both a functionality-oriented and a controls-oriented approach to gain a more complete understanding of the effects of their choices on overall performance. / by Joseph M. Morrow. / 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 60-62). / Increasing concerns regarding aircraft noise has encouraged the push to reduce noise via operational adjustments. The objective here is thus to expand analysis capabilities to enable modeling of the impact on aircraft noise due to advanced operational approach procedures, such as delayed deceleration approaches and thrust cutback scheduling on takeoff, for both current and future aircraft designs. Current industry standard noise models rely on flight test data interpolation and do not fully capture noise impacts from airframe configuration or advanced operational techniques. This is critical for noise assessment because airframe noise becomes a significant factor relative to the low thrust levels characteristic of advanced operational approaches. This method also limits the ability to assess new aircraft designs. Therefore, a new method combining aircraft sizing and performance tools with NASA's Aircraft NOise Prediction Program (ANOPP) has been developed to capture those noise impacts. ANOPP is used because of its capability of computing noise received at ground observers due to both engines and airframe of aircraft flying any flight procedure. Inputs into ANOPP are the aircraft geometry, the flight procedure, and the engine performance during the flight procedure. The Transport Aircraft System OPTimization (TASOPT) model is used to compute the engine performance inputs into ANOPP via first principles, physics-based methods. A separate tool was developed to compute the specifics of the flight procedure (max glide slope obtainable for a particular velocity and configuration, required thrust levels, etc.) based on drag polar supplied either by the Base of Aircraft Data (BADA 4) for current aircraft or by TASOPT for new aircraft. Benefits of this modeling framework include the flexibility in the aircraft and procedure analyzed and the ability to predict the noise of future aircraft configurations without relying on existing data. Both the noise impacts of a sample advanced operational flight procedure and in a future aircraft fleet have been assessed with this model. Next steps include further use of this model to evaluate the noise benefits or detriments of advanced operational approaches. / by Jacqueline L. Thomas. / S.M.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 2004. / Leaf 157 blank. / Includes bibliographical references (leaves 123-124). / A motivation exists to formulate and implement new tools and methodologies to address the problem of congestion in the National Airspace System (NAS). This thesis presents a novel methodology for allocating aircraft among En Route flight levels as a means to mitigate air traffic congestion and stakeholder operating costs. The core of the methodology is a decision-aiding tool comprised of a Mixed-Integer Linear Program (MILP) that is solved using a an A* Search-based Branch & Bound framework. Two metrics, measuring cumulative delay reduction and fuel burn savings, are used to benchmark the performance of the methodology. A combination of these two metrics is also explored as a means to minimize overall airline operating costs. A subsection of the Northeast Corridor is modeled and forms part of the analytic structure used to quantify the potential benefits of the proposed methodology. Simulations are generated from these models in order to gain an understanding of the benefits as they relate to varying NAS conditions. The following scenarios were modeled: 1) A baseline single jetway corridor, 2) Reduced Vertical Separation Minimum (RVSM), 3) Miles in Trail (MIT) restrictions on corridor traffic, and 4) the merging of Terminal Area air traffic with En route air traffic. Thus, this research also provides a preliminary, quantitative measure of the delay reduction, fuel burn savings and operating cost savings possible under each scenario, within a NAS corridor setting. Results indicate that 8.5 minutes of delay reduction per flight can be achieved when minimizing air traffic delay. Similarly, 16.47 kg/min of fuel burn savings per flight can be achieved when minimizing air traffic fuel burn. Instituting RVSM procedures result in an additional 45% of delay / (cont.) reduction. Imposing MIT restrictions result in a 41% loss of delay reduction savings. These results were obtained for corridor simulations of 30 minutes in duration. Finally, the methodology is shown to be effective for use as a decision-aiding tool to merge air traffic streams. / by Antonio Manuel Abad. / S.M.

Thesis: Ph. D., Massachusetts Institute of Technology, Department of Aeronautics and Astronautics, 2016. / This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections. / Cataloged from student-submitted PDF version of thesis. / Includes bibliographical references (pages 249-263). / Developmental product testing currently evaluates system safety the same way it evaluates system performance: it attempts to isolate individual components' behaviors to evaluate their reliability. However, today's systems are often irreducible because of their complexity, leaving current practices ineffective at identifying safety deficiencies. Evolving to a modern systems-based hazard analysis is important for product development. Products stand to benefit during the testing stage, before initial fielding. In test, designs meet operation for the first time, and use practices and organizational influences both contribute to the safety of the system. By evaluating safety as an emergent property, hazards that emerge because of the testing process itself can be mitigated, and hazards that exist because of the inherent system design and use philosophy can be identified and traced throughout development and fielding. System-Theoretic Process Analysis (STPA), developed by Nancy Leveson at the Massachusetts Institute of Technology, is a modern hazard analysis technique that identifies unsafe scenarios in a system in order to generate requirements to eliminate or control those scenarios. It improves on traditional reductionist approaches that treat accident causation only as a linear chain of events or probabilistic occurrence of simultaneous component failures (including human error). While systems-based and complete, STPA could benefit from additional guidance, particularly in the identification of human contributions to accidents. The present research begins by extending STPA to include more guidance for the controller analysis, including refinements to the process model, fundamental human-engineering considerations, and socio-organizational influences. Next, Leveson's organizational control structure example is updated to include a test stage that serves as an intermediary between design and field use. Model inclusion criteria are updated, and Explicit-Influence Maps are introduced as a tool to understand the organization and aid in hazard analysis. Finally, this research investigates the U.S. Air Force developmental testing enterprise and applies STPA to a product test. Results are compared to that of the test-safety planning and reporting techniques traditionally in use, and utility is assessed with a research survey administered to developmental test professionals. Keywords: STAMP, STPA, system safety, hazard analysis, product testing, test safety, problem reporting, safety certification / by Daniel R. Montes. / Ph. D.