Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 1991. / Includes bibliographical references (leaves 207-211). / by Glenn W. Law. / M.S.

Thesis: S.M., Massachusetts Institute of Technology, Department of Aeronautics and Astronautics, 2014. / Cataloged from PDF version of thesis. / Includes bibliographical references (pages 76-77). / Traditional hazard analysis techniques are grounded in reliability theory and analyze the human controller-if at all-in terms of estimated or calculated probabilities of failure. Characterizing sub-optimal human performance as "human error" offers limited explanation for accidents and is inadequate in improving the safety of human control in complex, automated systems such as today's aerospace systems. In an alternate approach founded on systems and control theory, Systems-Theoretic Process Analysis (STPA) is a hazard analysis technique that can be applied in order to derive causal factors related to human controllers within the context of the system and its design. The goal of this thesis was to extend the current human-controller analysis in STPA to benefit the investigation of more structured and detailed causal factors related to the human operator. Leveraging principles from ecological psychology and basic cognitive models, two new causal-factor categories-flawed detection and interpretation of feedback and the inappropriate affordance of action-were added to the human-controller analysis in STPA for a total of five categories. In addition, three of the five human-controller causal-factor categories were explicitly re-framed around those environmental and system properties that affect the safety of a control action-the process states. Using a proposed airspace maneuver known as In-Trail Procedure, a former STPA analysis was extended using this updated human-controller analysis. The updated analysis generated additional causal factors under a new categorical structure and led to new instances of specific unsafe control actions that could occur based on additional human factors considerations. The process, organization, and detail reflected in the resultant causal factors of this new human-controller analysis ultimately enhance STPA's analysis of the human operator and propose a new methodology structured around process states that applies equally as well to an automated controller. / by Cameron L. Thornberry. / S.M.

Thesis: S.M., Massachusetts Institute of Technology, Department of Aeronautics and Astronautics, 2016. / Cataloged from PDF version of thesis. / Includes bibliographical references (pages 73-77). / This thesis presents a high-order Implicit Large-Eddy Simulation (ILES) approach for simulating transitional aerodynamic flows. The approach consists of a hybridized Discontinuous Galerkin (DG) method for the discretization of the Navier-Stokes (NS) equations and a parallel preconditioned Newton-GMRES solver for the resulting nonlinear system of equations. The combination of hybridized DG methods with an efficient solution procedure leads to a high-order accurate NS solver that is competitive to alternative approaches, such as finite volume and finite difference codes, in terms of computational cost. The proposed approach is applied to transitional turbulent flows over a NACA 65-(18)10 compressor cascade and the Eppler 387 wing at Reynolds numbers up to 460,000. Grid convergence studies are presented and the required resolution to capture transition at different Reynolds numbers is investigated. Numerical results show rapid grid convergence and excellent agreement with experimental data. Focus is also placed on analyzing the structure of the boundary layer and the mechanism that causes transition to turbulence. Two-dimensional unstable modes in the form of Tollmien-Schlichting and Kevin-Helmholtz instabilities are found to be responsible for natural transition to turbulence through a laminar separation bubble. In short, this thesis aims to demonstrate the potential of high-order ILES for simulating transitional aerodynamic flows. This will be illustrated through numerical results and supported by theoretical considerations. / by Pablo Fernández. / S.M.

Thesis: S.M., Massachusetts Institute of Technology, Department of Aeronautics and Astronautics, 2016. / Cataloged from PDF version of thesis. / Includes bibliographical references (pages 71-73). / Allocating limited resources in a fair and efficient manner is crucial to the functioning of the air transportation system. Limited arrival and departure capacity at airports is one of the major drivers of congestion. The Ground Holding Problem refers to the problem of efficiently allocating landing slots during periods of reduced capacity. In this thesis, we propose a new model of the Ground Holding Problem. This formulation accounts for fairness in slot allocation and operational constraints, while being robust to the duration and severity of the disruption. The performance of this new method is evaluated using operational flight data. / by Karthik Kavassery Gopalakrishnan. / S.M.

Thesis (Sc. D.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 2003. / Includes bibliographical references (p. 195-204). / There is growing demand for high-reliability embedded systems that operate robustly and autonomously in the presence of tight real-time constraints. For robotic spacecraft, robust plan execution is essential during time-critical mission sequences, due to the very short time available for recovery from anomalies. Traditional approaches to encoding these sequences can lead to brittle behavior under off-nominal execution conditions, due to the high level of complexity in the control specification required to manage the complex spacecraft system interactions. This work describes timed model-based programming, a novel approach for encoding and robustly executing mission-critical spacecraft sequences. The timed model-based programming approach addresses the issues of sequence complexity and unanticipated low-level system interactions by allowing control programs to directly read or write "hidden" states of the plant, that is, states that are not directly observable or controllable. It is then the responsibility of the program's execution kernel to map between hidden states and the plant sensors and control variables. This mapping is performed automatically by a deductive controller using a common-sense plant model, freeing the programmer from the error-prone process of reasoning through a complex set of interactions under a range of possible failure situations. Time is central to the execution of mission-critical sequences; a robust executive must consider time in its control and behavior models, in addition to reactively managing complexity. / (cont.) In timed model-based programming, control programs express goals and constraints in terms of both system state and time. Plant models capture the underlying behavior of the system components, including nominal and off-nominal modes, probabilistic transitions, and timed effects such as state transition latency. The contributions of this work are threefold. First, a semantic specification of the timed model-based programming approach is provided. The execution semantics of a timed model-based program are defined in terms of legal state evolutions of a physical plant, represented as a factored Partially Observable Semi-Markov Decision Process. The second contribution is the definition of graphical and textual languages for encoding timed control programs and plant models. The adoption of a visual programming paradigm allows timed model-based programs to be specified and readily inspected by the systems engineers in charge of designing the mission-critical sequences. The third contribution is the development of a Timed Model-based Executive, which takes as input a timed control program and executes it, using timed plant models to track states, diagnose faults and generate control actions. The Timed Model-based Executive has been implemented and demonstrated on a representative spacecraft scenario for Mars entry, descent and landing. / by Michel Donald Ingham. / Sc.D.

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 1988. / Vita. / Includes bibliographical references. / by Kiran R. Magiawala. / M.S.

Massachusetts Institute of Technology. Dept. of Aeronautics and Astronautics. Thesis. 1969. Ph.D. / MICROFICHE COPY ALSO AVAILABLE IN AERO LIBRARY. / Lacking p. 83-84 and 97-98. Vita. / Bibliography: leaves 64-66. / Ph.D.

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 1989. / Includes bibliographical references (leaves 85-87). / by Vincent Hubert Garnier. / M.S.

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 1992. / Includes bibliographical references (leaves 74-76). / by Aaron J. Gleixner. / M.S.

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 1993. / Vita. / Includes bibliographical references (leaves 96-97). / by Michael S. Pavloff. / M.S.