Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 2006. / Includes bibliographical references (p. 59-60). / The design of hypersonic airbreathing aircraft pushes the envelope of current state-ofthe-art aerospace propulsion and materials technology. Therefore, these aircraft are highly integrated to produce adequate thrust, reduce drag, and limit surface heating. Consequently, every aircraft component (e.g., wings, fuselage, propulsion system) is sensitive to changes in every other component. Including Radar Cross Section (RCS) considerations further complicates matters. During preliminary design, this requires the rapid analysis of different aircraft configurations to investigate component interactions and determine performance trends. This thesis presents a framework and accompanying software for performing such an analysis. The intent is to optimize a hypersonic airbreathing aircraft design in terms of aerodynamic performance and RCS. Computational Fluid Dynamics (CFD) and Computational Electromagnetics (CEM) are the two main framework software components. CFD simulates airflow around the aircraft to analyze its aerodynamic performance. Alternately, CEM simulates the electromagnetic signature of the aircraft to predict its RCS. The framework begins with the generation of a three-dimensional computer aided design aircraft model. Next, a grid generator discretizes this model. The flow simulation is performed on this grid and the aircraft's aerodynamic characteristics are determined. Flow visualization aids this determination. Then, aircraft geometry refinements are made to improve aerodynamic performance. Afterward, CEM is performed on aerodynamically favorable designs at various aspect angles and frequencies. RCS values are determined and used to rank the different configurations. Also, inverse synthetic aperture radar images are generated to locate major scattering centers and aid the design refinement. The design loop continues in this fashion until an acceptable aircraft design is achieved. The NASA X-43A test vehicle was used to validate this preliminary design framework. / by Daniel L. DiCara. / S.M.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 2011. / Cataloged from PDF version of thesis. / Includes bibliographical references (p. 115-116). / The objective of stochastic process design is to strategically identify, measure, and reduce sources of uncertainty to guide the development of complex systems. Fundamental to this design approach is the idea that system development is driven by measurable characteristics called quantities of interest. These quantities of interest collectively describe the state of system development and evolve as the system matures. This thesis provides context for the contributions of quantities of interest to a stochastic process view of complex system development using three space hardware development projects. The CASTOR satellite provides the opportunity for retrospective identification of quantities of interest and their evolution through time. As a complement to CASTOR, the preliminary design of the REXIS x-ray spectrometer provides the foundation for applying stochastic process approaches during the early phases of system development. Lastly, a spacecraft panel structural dynamics experiment is presented that illustrates analysis techniques commonly employed in stochastic process analysis. / by George Ralph Sondecker, IV. / 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. 93-98). / This thesis presents an overview of the design process for creating greedy decentralized task allocation algorithms and outlines the main decisions that progressed the algorithm through three different forms. The first form was called the Sequential Greedy Algorithm (SGA). This algorithm, although fast, relied on a large number of iterations to converge, which slowed convergence in decentralized environments. The second form was called the Consensus Based Bundle Algorithm (CBBA). CBBA required significantly fewer iterations than SGA but it is noted that both still rely on global synchronization mechanisms. These synchronization mechanisms end up being difficult to enforce in decentralized environments. The main result of this thesis is the creation of the Asynchronous Consensus Based Bundle Algorithm (ACBBA). ACBBA broke the global synchronous assumptions of CBBA and SGA to allow each agent more autonomy and thus provided more robustness to the task allocation solutions in these decentralized environments. / by Luke B. Johnson. / S.M.

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 1997. / Includes bibliographical references (p. 92-93). / by Dawn Hastreiter. / M.S.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 2010. / Cataloged from PDF version of thesis. / Includes bibliographical references (p. 71-72). / This thesis examines an axial compressor body force representation constructed from 3D CFD calculations. The radial distribution of body forces is compared to that of a body force representation based on axisymmetric streamline curvature (SLC) calculations, and shown to be in qualitative agreement except in the vicinity of the blade tip. In terms of stall inception type and stall point, computations based on both representations exhibit agreement with rig test data. A parametric study is undertaken in which the magnitude of the forces in the blade tip region of both representations is reduced so as to obtain reductions in compressor pressure rise similar to those observed experimentally due to increased tip clearance. It is shown that on a back-to-back basis, a given change to the end wall forces produces similar effects on the computed stall point, whether the underlying body force representation derives from 3D CFD or SLC. Based on this result one route to capturing effects of tip clearance on stall prediction can be the development of a tip clearance body force model for use in conjunction with SLC calculations. / by Jonathan Kerner. / S.M.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 2002. / Includes bibliographical references (p. 189-190). / by Theodore R. Ducyman. / S.M.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, June, 2010. / "May 2010." Cataloged from PDF version of thesis. / Includes bibliographical references (p. 87-90). / Sensor networks used for activities like border security, search and rescue, planetary exploration, commonly operate in harsh environments for long durations, where human supervision is minimal. A major challenge confronting such devices is providing adequate and reliable power supply required for long durations. This research considers the feasibility of a miniature Proton Exchange Membrane (PEM) fuel cell system coupled with battery to supply power for long life missions. The focus of this research is to prove the feasibility of long-life, self-contained power-supplies using miniature fuel cells for low-power distributed sensor networks. In this research, the performance of fuel cell power-supplies weighing not more than a few hundred grams is studied. The performance of the PEM fuel cell is modeled, analyzed and validated using experimental results. The feasibility of the fuel cell power systems are studied for two reference missions - one on the lunar surface and the other in the desert regions of Negev, Israel. This research analyzes the use of passive methods to achieve thermal, air and water management for PEM fuel cells supplying power to these field sensors. The results of this study suggest that the proposed fuel cell power system is capable of providing power to sensor modules in challenging field conditions with operational lives extending from many months to years. The scope of this concept can be extended to power devices such as micro-robots and small unmanned aerial vehicles operating in extreme environmental conditions for sustained periods of time. / by Kavya Kamal Manyapu. / S.M.

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 1991. / Includes bibliographical references (p. 83-87). / by Paula S. Aqui. / M.S.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 2008. / Includes bibliographical references (p. 189-197). / Small unmanned aerial vehicles (UAVs), equipped with navigation systems and video capability, are currently being deployed for intelligence, reconnaissance and surveillance missions. One particular mission of interest involves computing location estimates for targets detected by onboard sensors. Combining UAV state estimates with information gathered by the imaging sensors leads to bearing measurements of the target that can be used to determine the target's location. This 3-D bearings-only estimation problem is nonlinear and traditional filtering methods produce biased and uncertain estimates, occasionally leading to filter instabilities. Careful selection of the measurement locations greatly enhances filter performance, motivating the development of UAV trajectories that minimize target location estimation error and improve filter convergence. The objective of this work is to develop guidance algorithms that enable the UAV to fly trajectories that increase the amount of information provided by the measurements and improve overall estimation observability, resulting in proper target tracking and an accurate target location estimate. The performance of the target estimation is dependent upon the positions from which measurements are taken relative to the target and to previous measurements. Past research has provided methods to quantify the information content of a set of measurements using the Fisher Information Matrix (FIM). Forming objective functions based on the FIM and using numerical optimization methods produce UAV trajectories that locally maximize the information content for a given number of measurements. In this project, trajectory optimization leads to the development of UAV flight paths that provide the highest amount of information about the target, while considering sensor restrictions, vehicle dynamics and operation constraints. / (cont.) The UAV trajectory optimization is performed for stationary targets, dynamic targets and multiple targets, for many different scenarios of vehicle motion constraints. The resulting trajectories show spiral paths taken by the UAV, which focus on increasing the angular separation between measurements and reducing the relative range to the target, thus maximizing the information provided by each measurement and improving the performance of the estimation. The main drawback of information based trajectory design is the dependence of the Fisher Information Matrix on the true target location. This issue is addressed in this project by executing simultaneous target location estimation and UAV trajectory optimization. Two estimation algorithms, the Extended Kalman Filter and the Particle Filter are considered, and the trajectory optimization is performed using the mean value of the target estimation in lieu of the true target location. The estimation and optimization algorithms run in sequence and are updated in real-time. The results show spiral UAV trajectories that increase filter convergence and overall estimation accuracy, illustrating the importance of information-based trajectory design for target localization using small UAVs. / by Sameera S. Ponda. / S.M.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 2011. / Cataloged from PDF version of thesis. / Includes bibliographical references (p. 89-91). / Auction theory is a very interesting topic which studies mechanisms of various formats for buying and selling goods. There are all kinds of mechanisms covered in the ambit of auction theory, ranging from sealed bid auctions like first-price or second price auctions, to open bid auctions like the English or Dutch auctions. One interesting kind of auction is the all-pay auction, in which, as the name suggests, all the players pay their bids. Analysis of all-pay auctions with virtual money has so far been neglected in the auction theory literature. However, it can be used to design a mechanism with a wide variety of applications including equitable resource allocation, and fairer systems for legislation and corporate management. In this thesis, we shall present this novel mechanism, analyze it in a game-theoretic framework and consider the variants of the problem including the perfect and imperfect information cases. Furthermore, we shall outline how to find the equilibrium bidding strategies for this mechanism which lead to equitable distribution of resources. One possible application of this is in equitable resource allocation, such as in a battlefield where different agents have competing needs for limited resources to complete their missions. Finally, we shall draw the connection between this mechanism, and the process of voting in the legislature or the company board rooms. Currently, a party needs just more than 50% of seats in the legislature to control 100% of the bills. Similarly, a shareholder needs just 51% of shares to completely control the company. We shall show how it is possible to modify these voting systems, using the proposed mechanism to enable even the minority players to have an equitable say in the decisions. / by Rajarshi Ghosh Dastidar. / S.M.