Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 2012. / Cataloged from department-submitted PDF version of thesis. 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. / Includes bibliographical references (p. 91-93). / General aviation (GA) is an important component of aviation in the United States. In 2011, general aviation and air taxi operations represented 63% of all towered operations in the United States, while commercial aviation was responsible for 34% of those operations. It is clear that GA is a considerable component of the national airspace and airport system, even when only accounting for towered operations. Because of this significant presence, insight into GA is relevant to issues in air traffic management, air transportation infrastructure, and aviation safety, among others. Beyond the operational aspect, GA is of significance to society as a whole and to other stakeholders, including pilots groups, aircraft manufacturers, and the work force. In 2009, general aviation generated 496,000 jobs and its total economic contribution to the U.S. economy was valued at $76.5 billion. However, a comparison of general aviation's impact on jobs and on the economy between 2008 and 2009, shows a 20% decrease in jobs and a 21% decrease in total economic impact in the course of a year. There is also a significant decreasing trend in the active pilot population, along with steady decreases in GA flight hours and towered operations. The objective of this thesis is to explore the details of these changing trends and to determine what drives and what hinders general aviation activity in the country. A combination of data analysis and the development of a survey administered to general aviation pilots shed light on what has driven activity in the past on a national scale, what factors affect an individual pilot's level of activity, and what challenges the general aviation community faces in the future. / by Kamala Irene Shetty. / S.M.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 2002. / Includes bibliographical references (p. 145). / by Troy D. Downen. / 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 243-250). / Electrosprays of the pure-ion variety embody a unique collection of attributes that have compelled interest in derivative technologies across a spectrum of applications ranging from Focused Ion Beams (FIB) to microrocketry. Unlike conventional colloid sources (i.e., so-called cone-jets or others sources from which droplets typically emanate), pure ion sprays are commonly characterized by narrow distributions of high specific charge and nominal energy deficits as a result of their evaporative mechanisms. Among other properties of the spray, these are known to enable well-behaved optics (e.g. for nanometric patterning with FIB) and low power overhead (e.g. for efficient electrical-to-kinetic energy transduction in microrocketry) while also providing for innate simplicity and spatial compactness. In spite of their potential for paradigm-shifting impact, the practicality of contemporary pure-ion sources has been tempered by issues relating to reliability and predictability. In contrast to droplet emission, for example, empirical studies strongly suggest that pure-ion modes are only permissible under special sets of circumstances and that important beam qualities (namely the stability but also the current) are sensitive functions of the meniscus configuration. The difficulty in controlling these modes is somewhat abated through the use of fluids like ionic liquids (IL), particularly in connection with several heuristics that have emerged, but the process remains substantially fickle. This is believed to owe most directly to an undeveloped physical understanding. While the physics that govern conventional colloid sources are at least functionally understood at this point, an analogous grasp of their ion relatives has proven elusive. The purpose of this thesis is to begin addressing this issue by way of rigorous theoretical investigations, with the ultimate aim of offering deeper fundamental insight and additional recourse to future design initiatives beyond the existing set of over-simplified heuristics. In this thesis we first conduct a survey of potential contributors to the very multi-physical phenomenon of charge evaporation and identify key influences through basic order-of-magnitude analyses. These are used to inform the formulation of a detailed mathematical framework that is subsequently leveraged in the exploration of evaporation behaviors for a prototypical ionic liquid meniscus across a range of field, media, and hydraulic conditions. The results uncover a previously uncharted family of highly-stressed but ostensibly stable solutions for the problem of a volumetrically-unconstrained source. These appear to be confined to a particular subregion of the global parameter space that emphasizes thoughtful sizing of the meniscus and architecting of the feeding system. The impedance aspect of the latter, in particular, is believed to play a critical role in steady emission when large scale disparities, which are common in practical settings, exist across the parent meniscus. Additional influences that are often neglected in the literature, such as that of the liquid permittivity, are also elucidated and shown to play meaningful roles in evaporation. We conclude by outlining a reasonably comprehensive set of conditions that should be met for steady emission and substantiate these with tangible evidence from our studies. / by Chase Coffman. / Ph. D.

Thesis: S.M., Massachusetts Institute of Technology, Department of Aeronautics and Astronautics, 2017. / Cataloged from PDF version of thesis. / Includes bibliographical references (pages 166-170). / Current human motion measurement systems using inertial measurement units (IMUs) typically rely on precise alignment, static calibration poses, or dynamic calibration motions. Muller et al. recently proposed a method for online calibration of the human elbow anatomical joint axes via decomposition of angular velocity measurements. This thesis evaluated this calibration-free method in the context of two motion types. First, the method is evaluated with human-generated motions common to occupational rehabilitation, to investigate activities of daily living (ADLs) as online calibration motions. Second, the method is evaluated with parameterized sinusoidal motion, to investigate amplitudes and frequencies of motions that yield robust axis estimations. It was found for the axis of interest, high on-axis motion and low off-axis motion lead to precise axis estimation and high accuracy estimation of the pronation/supination elbow axis. Further, high off-axis motion and low on-axis motion yielded imprecise axis estimation and inaccurate estimation of both the flexion/extension and pronation/supination elbow axes. A comparative study of different filtering methodologies to the estimation of upper extremity human motion was also performed. Compared to a motion capture truth, the Extended Kalman Filter (EKF) and Unscented Kalman Filter (UKF) were found to perform similarly. An implemented particle filter (PF) was found to perform better than both the EKF and UKF, and on the order of accuracy of a manufacturers black-box algorithm. This work is the first to evaluate a particle filter in the estimation of human motion by inertial sensors. The particle filter was then subject to a sensitivity analysis of the error of its estimated 3D orientation to its underlying algorithm inputs, namely, the accelerometer and magnetometer uncertainties, and number of particles. Recommended operational levels for these parameters are reported. Future work will combine the Muller auto-calibration method, robust IMU orientation filters, and knowledge of appropriate online motions to develop an IMU bias correction method for long periods of measurement. / by Timothy M. McGrath. / S.M.

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 1990. / Title as it appears in the M.I.T. Graduate List, June, 1990: An application of the A* search technique to trajectory optimization. / Includes bibliographical references (leaves 87-88). / by Craig K. Niiya. / M.S.

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 1997. / Includes bibliographical references (p. 199-201). / by Christopher John McLain. / M.S.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 2011. / Cataloged from PDF version of thesis. / Includes bibliographical references (p. 97-102). / In producing a stop consonant, a soft tissue articulator, such as the lower lip, the tongue tip, or the tongue body, is raised to make an airtight closure. Stevens [I] pp 32 9-3 30 hypothesized that the interaction of the air pressure with the yielding soft-tissue wall would lead to a plateau-shaped release trajectory, and the duration of the plateau is progressively longer for bilabial, alveolar, and velar (Fig. 1-1). This thesis analyzes the pressure-wall interaction when a stop closure is released. Three flow models are implemented to derive the release trajectory: quasi-steady incompressible, unsteady incompressible, and unsteady compressible flow. Results from the models confirm Stevens' hypothesis. In the unsteady flow models, this thesis contributes a new method - deformable control volume analysis - to the pressure-wall interaction for small openings. This method may also be applied to quantify the unsteady effect during the closing and opening of the vocal folds and during the initial transient phase of a stop consonant, when the cross-sectional area is small. Indirect means of measuring an unknown parameter in the pressure-wall interaction analysis is discussed with the aid of a closure model which derives the condition of retaining a complete closure against air pressure buildup. In comparison with real speech data, an acoustic measure is defined for determining the duration of the frication noise of voiceless alveolar and velar stop consonants in syllable initial positions. This newly defined measure is based on the time variation of the average FFT magnitude in the whole frequency range and the magnitude in a 50-Hz-wide frequency band containing the front cavity resonance for the signal in every 5 milliseconds (a moving 5-ms window). This measure is found applicable to 25 releases out of 32 releases from TIMIT database. The means of the collected durations are found closest to the estimated duration calculated with the unsteady compressible flow model. / by Lan Chen. / S.M.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 2007. / Includes bibliographical references (p. 165-169). / This thesis describes the design and performance results for the P-NMR fault tolerant avionics system architecture being developed at Draper Laboratory. The two key principles of the architecture are robust software partitioning (P), as defined by the ARINC 653 open standard, and N-Modular Redundancy (NMR). The P-NMR architecture uses cross channel data exchange and voting to implement fault detection, isolation and recovery (FDIR). The FDIR function is implemented in software that executes on commercial-off-the-shelf (COTS) hardware components that are also based on open standards. The FDIR function and the user applications execute on the same processor. The robust partitioning is provided by a COTS real-time operating system that complies with the ARINC 653 standard. A Triple Modular Redundant (TMR) prototype was developed and various performance metrics were collected. Evaluation of the TMR prototype indicates that the ARINC 653 standard is compatible with an NMR and FDIR architecture. Application partitions can be considered software fault containment regions which enhance the overall integrity of the system. The P-NMR performance metrics were compared with a previous Draper Laboratory design called the Fault Tolerant Parallel Processor (FTPP). This design did not make use of robust partitioning and it used proprietary hardware for implementing certain FDIR functions. The comparison demonstrated that the P-NMR system prototype could perform at an acceptable level and that the development of the system should continue. This research was done in the context of developing cost effective avionics systems for space exploration vehicles such as those being developed for NASA's Constellation program. / by Brendan Anthony O'Connell. / 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 140-161). / Air transportation is an integral part of the economy and the transportation infrastructure. However, aircraft activity at airports generates CO2 emissions that affect the climate and other pollutants that affect air quality and human health. The focus of this thesis is to enable the reduction of the air quality impacts of aircraft operations at airports by (1) advancing the understanding of the relationship between aircraft activity and its air quality impacts and (2) evaluating the air quality benefits of controlling aircraft operations. There are atmospheric conditions where decreasing fuel burn (which is directly proportional to CO2 emissions) results in increased population exposure to fine particulate matter (PM2.5) and ozone (O3). This thesis quantifies the duration and magnitude of the tradeoffs between CO2 emissions and population exposure. The research complements current studies that optimize aircraft operations at airports for CO2 emissions but have not quantified the air quality implications of doing so. This raises the possibility of reducing the air quality impacts of airports beyond focusing only on minimizing fuel burn. Next, this thesis characterizes the atmospheric conditions that give rise to tradeoffs between emissions and population exposure to ozone. The ozone exposure response to nitrogen oxide (NOx) and Volatile Organic Compound (VOC) emissions is quantified as a function of ambient NOx and VOC concentrations using ozone exposure isopleths. This is the first time that ozone exposure isopleths are created for all locations in the US, using emission sensitivities from the adjoint of an air quality model. Metrics are calculated based on the isopleths which can be used to determine whether NOx and VOC emission reductions will improve ozone exposure or be counter-productive and the optimal NOx/VOC reduction ratio. Finally, this thesis calculates, for the first time, the air quality and climate benefits of pushback control and de-rated takeoffs for simulated aircraft operations at the Detroit Metropolitan Wayne County Airport (DTW). Operations are also optimized for minimum air quality, environmental and fuel combustion-related costs. The results show that the gate holding strategy is effective in mitigating the environmental impacts of taxi operations at airports, reducing CO2 emissions and air quality impacts by 35-40% relative to a baseline without gate holds. De-rated takeoffs at 75% thrust are effective in reducing the air quality impacts of takeoff operations by 19% but increase fuel burn by 3% relative to full-thrust takeoffs. Environmental costs are minimized with average optimal thrust setting of 81%, while maintenance cost savings are estimated to be 2 orders of magnitude larger than the increase in fuel costs from de-rated takeoffs. / by Akshay Ashok. / Ph. D.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 2008. / Includes bibliographical references (p. 81-84). / Small aircraft engines traditionally have poorer performance compared to larger engines, which until recently, has been a factor that outweighed the aerodynamic benefits of commoditized and distributed propulsion. Improvements in the performance of small engines have, however, prompted another look at this old concept. This thesis examines aspects of aircraft engines that may have application to commodity thrust or distributed propulsion applications. Trends of engine performance with size and time are investigated. These trends are further extended to justify parameter choices for conceptual engines of the current, mid-term (10 years) and far-term (20 years). Uninstalled and installed performances are evaluated for these engines, and parametric studies are performed to determine the most influential and limiting factors. It is found that scaling down of engines is detrimental to SFC and fuel burn, mainly due to the Reynolds number effect. The more scaling done, the more prominent the effect. It is determined that new technology such as higher TIT, OPR and turbomachinery [eta]poly's for small aircraft engines enable the operation of larger bypass ratios, which is the most influential parameter to SFC and fuel bum. The increase of bypass ratio up to a value of 8 is found to be effective for such improvement. SFC decrease from the current to mid-term model is found to be ~20% and ~9% from mid-term to far-term. Range and endurance improvements are found to be ~30% and ~10% respectively for the mission examined. Finally, the mid-term engine model has performance comparable to that of a current, larger state-of-the-art engine, thus suggesting that improvement in small gas turbine technology in the next 10 years will make the application of commodity thrust or distributed propulsion an attractive option for future aircraft. / by Nicholas Y.S. Chan. / S.M.