Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 2005. / Includes bibliographical references (leaves 101-105). / Traditional multidisciplinary design optimization (MDO) approaches do not examine the costs associated with damage due to environmental factors and are usually implemented to examine one aircraft. The Environmental Design Space (EDS), an MDO tool, needs cost models that can incorporate the damage cost benefits of environmentally driven design changes both on a single aircraft and throughout a model fleet. It is important that the EDS framework also has a capability to assess the impact of future environmental technologies. Operating cost and fleet representation modules are created for the Environmental Design Space to calculate aggregated fleet effects for operating cost and emissions for current and evolving aircraft fleet. A case study involving a cost-benefit analysis of a NOx stringency mandate is conducted using the modules to assess the limitations of EDS. To assess the impacts of future environmental technologies, a real options framework is created using financial theory and applied to an engineering context. This framework is then used to derive a current monetary value for the option to include a noise reduction technology, trailing edge fan blowing, into an aircraft system. / (cont.) Examining the trade-offs of the three differently designed replacement aircraft, the operating cost and fleet representation modules show that the minimum NOx aircraft has less of a cost-benefit fleet impact than that of the minimum fuel burn and minimum take-off weight. These results demonstrate a major trade-off between performance and environmental factors. The operating cost and fleet representation modules along with EDS assist in the design of aviation environmental policies by examining scenario fleet impacts. The real options framework using Monte Carlo software calculates the option value of incorporating new technology into the fleet. / by Christopher Dennis Hynes. / S.M.

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 1995. / Includes bibliographical references (p. 259-267). / by Scott Thoams Wallace. / M.S.

Thesis: S.M., Massachusetts Institute of Technology, Department of Aeronautics and Astronautics, 2015. / Cataloged from PDF version of thesis. / Includes bibliographical references (pages 171-177). / Most satellites on-orbit today are not intended to physically approach or interact with other spacecraft. However, the robotic servicing of orbiting assets will be an economically desirable (and often scientifically necessary) capability in future space enterprises. With the right set of tools and technologies, satellites will be able to autonomously refuel, repair, or replace each other. This has the potential to extend mission lifetimes, reduce orbital debris and make space more sustainable. Spacecraft may also assemble on-orbit into larger aggregate spaceflight systems, with applications to sparse aperture telescopes, solar power stations, fuel depots and space habitats. The purpose of this thesis is to address the highest risk elements associated with the docking and servicing of satellites: the sensors, actuators, and associated algorithms. First, a peripheral agnostic robotics platform is introduced, upon which a suite of technology payloads may be developed. Next, a flight qualified docking port for small satellites is presented, and the results detailing its operation in a relevant environment are discussed. In addition, we review a high precision relative sensor designed to enable boresight visual docking. The measurements from this optical camera are applied to a nonlinear estimator to provide the highly accurate sensing necessary for docking. Finally, a free-flying robotic arm is examined and modeled as an experimental payload for the SPHERES Facility on the International Space Station. / by Duncan Lee Miller. / S.M.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 2004. / Includes bibliographical references (p. 109-111). / This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections. / Limit analysis is relevant in many practical engineering areas such as the design of mechanical structures or the analysis of soil mechanics. Assuming a rigid, perfectly-plastic solid subject to a static load distribution, the problem of limit analysis consists of finding the minimum multiple of this load distribution that will cause the body to collapse. This collapse multiplier results from solving an infinite dimensional saddle point problem, where the internal work rate is maximized over an admissible set of stresses -defined by a yield condition- and minimized over the linear space of kinematically admissible velocities for which the external work rate equals the unity. When strong duality is applied to this saddle point problem, the well-known convex (and equivalent) static and kinematic principles of limit analysis arise. In this thesis, an efficient procedure to compute strict upper and lower bounds for the exact collapse multiplier is presented, with a formulation that explicitly considers the exact convex yield condition. The approach consists of two main steps. First, the continuous problem, under the form of the static principle, is discretized twice (one per bound) by means of different combinations of finite element spaces for the stresses and velocities. For each discretization, the interpolation spaces are chosen so that the attainment of an upper or a lower bound is guaranteed. The second step consists of solving the resulting discrete nonlinear optimization problems. Towards this end, they are reformulated into the canonical form of Second-order Cone Programs, which allows for the use of primal-dual interior point methods that optimally exploit the convexity and duality properties of the limit analysis / (cont.) model and guarantee global convergence to the optimal solutions. To exploit the fact that collapse mechanisms are typically highly localized, a novel method for adaptive meshing is introduced based on local bound gap measures and not on heuristic estimates. The method decomposes the total bound gap as the sum of positive elemental contributions from each element in the mesh, and refines only those elements which are responsible for the majority of the numerical error. Finally, stand-alone computational certificates that allow the bounds to be verified independently, without recourse to the original computer program, are also provided. This removes the uncertainty about the reliability of the results, which frequently undermines the utility of computational simulations. The efficiency of the methodology proposed is illustrated with several applications in plane stress and plane strain, demonstrating that it can be used in complex, realistic problems as a supplement to other models. / by Héctor Ciria Suárez. / S.M.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 2004. / Includes bibliographical references (p. 77-80). / A micro-fabricated solid oxide fuel cell is currently being designed by the Micro-chemical Power Team(funded under the Multidisciplinary University Research Initiative(MURI) Research Program). In the current design a plate structure vital to power generation is exposed to harsh thermal operation conditions, making it susceptible to structural failure. This thesis investigates the mechanisms of its structural failure, develops tools and models to understand the mechanisms quantitatively, and gives suggestions to guide the design process with the models developed. The thesis begins with a brief overview of the principles of fuel cell operation, their associated operating conditions, along with a description of how these conditions may lead to structural failure. Next a representative structure of a portion of a fuel cell critical to power generation is analyzed, for a given temperature distribution. Different temperature distributions across the same structure are also analyzed. Results from these analyses are then used to provide guidance for the design process. Finally future directions for research are given. / by Tze Yung Andrew Ie. / S.M.

Thesis (S.M.)--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. 97-102). / The supply of clean water in remote and off-grid areas has been a major global challenge for humanity. Over 780 million people lack access to clean water [1]. However, a significant fraction of these people have access to undrinkable surface, brackish or sea water. A promising solution to this problem is to use photovoltaic powered reverse osmosis (PVRO) systems to purify this unsafe water to produce clean drinking water. However, high initial capital costs and a lack of commercial viability have prohibited these systems for commercial and daily use. For this approach to be feasible and reach large-scale commercial viability, PVRO systems need to be energy efficient and cost-competitive compared with reverse osmosis systems powered by conventional sources, such as diesel engines or electricity from the grid. The costs and energy consumption in a PVRO system can be significantly decreased by maximizing water production and minimizing the effects of membrane degradation to extend system life. The membrane degradation considered here is the fouling phenomenon in which suspended solids and dissolved substances collect on the surface and within the pores of the membrane thereby reducing its permeability This thesis describes an innovative approach to autonomously controlling and optimizing community scale PVRO systems by controlling membrane degradation due to fouling, using a self-optimizing condition based maintenance algorithm. Additionally, by exploiting the energy compliance of PVRO elements and actively controlling the individual components of the system, water production can be maximized. The compliance in a PVRO system has been found to significantly affect PVRO performance by reducing system efficiency and resulting in long startup delays in producing clean water. In this thesis, a controllable recovery ratio concept system has been presented. By actively controlling the PVRO system, an improvement of 47% over the existing performance of a fixed recovery ratio system has been shown in simulations. Use of condition based maintenance strategies show an improvement of over 10% in cumulative clean water production compared to scheduled quarterly maintenance and 58% over 1 year in cumulative clean water production compared to the case without any maintenance. This is interesting since typical community scale and point of use systems can be and are operated without periodic maintenance [2]. Combining the optimal power control and condition-based maintenance strategies, an improvement in water production of 85 % is shown for a July day in Boston over the MIT PVRO system. Finally, a self-optimizing condition based maintenance algorithm is proposed as the optimal solution to control membrane degradation due to fouling. / by Aditya Sarvanand Bhujle. / S.M.

Thesis: Ph. D., Massachusetts Institute of Technology, Department of Aeronautics and Astronautics, 2014. / Cataloged from PDF version of thesis. / Includes bibliographical references (pages 91-99). / In resource-constrained inferential settings, uncertainty can be efficiently minimized with respect to a resource budget by incorporating the most informative subset of observations - a problem known as active inference. Yet despite the myriad recent advances in both understanding and streamlining inference through probabilistic graphical models, which represent the structural sparsity of distributions, the propagation of information measures in these graphs is less well understood. Furthermore, active inference is an NP-hard problem, thus motivating investigation of bounds on the suboptimality of heuristic observation selectors. Prior work in active inference has considered only the unfocused problem, which assumes all latent states are of inferential interest. Often one learns a sparse, high-dimensional model from data and reuses that model for new queries that may arise. As any particular query involves only a subset of relevant latent states, this thesis explicitly considers the focused problem where irrelevant states are called nuisance variables. Marginalization of nuisances is potentially computationally expensive and induces a graph with less sparsity; observation selectors that treat nuisances as notionally relevant may fixate on reducing uncertainty in irrelevant dimensions. This thesis addresses two primary issues arising from the retention of nuisances in the problem and representing a gap in the existing observation selection literature. The interposition of nuisances between observations and relevant latent states necessitates the derivation of nonlocal information measures. This thesis presents propagation algorithms for nonlocal mutual information (MI) on universally embedded paths in Gaussian graphical models, as well as algorithms for estimating MI on Gaussian graphs with cycles via embedded substructures, engendering a significant computational improvement over existing linear algebraic methods. The presence of nuisances also undermines application of a technical diminishing returns condition called submodularity, which is typically used to bound the performance of greedy selection. This thesis introduces the concept of submodular relaxations, which can be used to generate online-computable performance bounds, and analyzes the class of optimal submodular relaxations providing the tightest such bounds. / by Daniel S. Levine. / Ph. D.

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 1988. / Bibliography: leaves 87-88. / by Yusuf Rezah Jafry. / M.S.

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 1992. / Includes bibliographical references (leaves 77-78). / by Gary S. Hufford. / M.S.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 1972. / Vita. / Includes bibliographical references. / Ph.D.