Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 2000. / Also available online at the MIT Theses Online homepage <http://thesis.mit.edu>. / Includes bibliographical references (p. 145-146). / This thesis deals with the manufacture of a 26-bladed 'active' rotor that will be used for developing an experimental database on turbomachinery aeroservoelastic phenomena, such as flutter and its control. The active rotor has blades made of two stress-bearing composite spars, aerodynamically shaped foam, piezoelectric actuators attached to the spar base and a root which allows the blade to be inserted into the rotor. The thesis analyzed the models developed for the active rotor blade design from previous studies and made suitable refinements in them. The following parameters were obtained - spar dimensions, their location and material, piezoelectric dimensions and material, foam material, and root structure and material. Next, technologies were developed for manufacturing the root and the twisted spar, packaging the piezoelectric actuators using copper-Kapton and bonding them to the spars, and wiring the spars and actuators. However, further investigation is necessary with regards to the issues of foam shaping, spar-foam attachment, and development of accurate leading and trailing edges of the blade. The final step involved testing the blade before and after spar-foam bonding. This required testing on the benchtop to obtain the blade performance limitations, and then testing it in vacuum while spinning inside a spin pit, which was constructed for this purpose. The latter gives the blade performance under rotation. The scope of the thesis is limited to the benchtop tests conducted on the active wired spars. Some of the blade and spin pit wiring issues need to be resolved before conducting the spin tests in vacuum. Also a rotor frame incorporating 26 active blades needs to developed to test under vacuum and in a wind tunnel. The results of the preliminary benchtop tests as well as the blade finite element model predict that the blade performance would be lower than the initial target. Several ways of improving its actuation capability considered were: (a) applying higher voltage with DC offset to the actuators, (b) using multi-wafer actuators, and (c) using active fiber composites. However, these issues need further work. The active rotor, when completed, will serve as a robust tool for aeroservoelastic testing over a significantly larger operating range than is currently possible. / by Debashis Sahoo. / S.M.

Thesis: S.M., Massachusetts Institute of Technology, Department of Aeronautics and Astronautics, February 2015. / Cataloged from PDF version of thesis. "February 2015." / Includes bibliographical references (pages 71-74). / Biofuels have the potential to mitigate the environmental impact of aviation and offer increased energy security through the displacement of conventional jet fuel. This study investigates strategies designed to reduce the production cost and lifecycle greenhouse gas (GHG) emissions of microalgae-derived HEFA jet fuel. Additionally, the global production potential of HEFA-J is quantified in order to assess the efficacy of microalgae as an energy crop. Impacts from the integration/scaling of microalgae cultivation were quantified by calculating avoided costs and GHG emissions from inputs displaced as a result of integration/scaling. Avoided costs and emissions associated with each impacted input were calculated in units of $/galHEFA-J and gCO₂e/MJHEFA-J, respectively. Results were summed to produce total impact values and resulting production cost/lifecycle emissions values of HEFA-J for each strategy investigated. Baseline results indicate that integration with wastewater treatment (WWT) facilities may reduce production cost and lifecycle GHG emissions of HEFA-J by 29.2% and >100%, respectively, in open pond systems. Integration with aquaculture processes may reduce production cost by 10.4% in open ponds. Scaling microalgae cultivation from 137 to 2192 barrels per day (BPD) results in a 22.7% reduction in production cost and a 32.0% reduction in lifecycle GHG emissions in open pond systems. Combining scaling and WWT integration methods in open ponds yields a 52.0% reduction in production cost and >100% lifecycle GHG emissions reduction. Global production potential of microalgae-derived HEFA-J is quantified through the summation of annual energy yields of cells at a 5 arc minute resolution. Results are constrained by geographically variable biological growth factors in addition to water/CO₂ transportation constraints, land availability and slope, and industrial CO₂ availability. Maximum jet and maximum distillate product slates were applied to total energy potential results to quantify global production potential of HEFA-J. Baseline results indicate that 27.5 EJHEFA-J/yr may be produced, or approximately 3 times the annual global aviation energy demand. / by Jacob L. Ames. / S.M.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 1998. / Includes bibliographical references (leaves 155-156). / by Raymond John Sedwick. / Ph.D.

Thesis: Ph. D., Massachusetts Institute of Technology, Department of Aeronautics and Astronautics, February 2016. / Cataloged from PDF version of thesis. "February 2015." / Includes bibliographical references (pages 162-173). / The recent development of neuromorphic vision sensors, which provide an asynchronous, high-speed alternative to conventional cameras has lead to a considerable amount of research into their applicability to robotic control systems. However, algorithms for onboard control of mobile robotic platforms such as automobiles or aircraft using these sensors are lacking and in fact almost all existing implementations keep the sensor stationary. This research has several objectives. First, to develop a rigorous understanding of how to use asynchronous temporal contrast vision sensors for heading regulation and tracking in such a way as to fully leverage the remarkable properties of these sensors including high bandwidth, low latency and low power consumption. Second, to provide a theoretical and experimental comparison between neuromorphic vision sensors and conventional cameras in the context of this problem. Finally, to describe and test algorithms for high-speed motion planning in cluttered environments using neuromorphic vision sensors. / by Erich Mueller. / Ph. D.

Thesis: S.M., Massachusetts Institute of Technology, Department of Aeronautics and Astronautics, 2016. / Cataloged from PDF version of thesis. / Includes bibliographical references (pages 103-105). / In this thesis, a priori convergence estimates are developed for outputs, output error estimates, and localizations of output error estimates for Galerkin finite element methods. Specifically, Continuous Galerkin (CG), Discontinuous Galerkin (DG), and Hybridized DG (HDG) methods are analyzed for the Poisson problem. A mixed formulation for DG output error estimation is proposed with improved convergence rates relative to the common approach utilizing statically condensed, p-dependent lifting operators. The HDG output error estimates are new and include the impact of stabilization. Comparisons to numerical results demonstrate (1) the sharpness of the estimates and (2) that the HDG estimates are approximately an order of magnitude more accurate than CG and DG. / by Hugh Alexander Carson. / S.M.

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 1964. / MICROFICHE COPY AVAILABLE IN AERO. / Includes bibliographical references (leaves 93-95). / by David Finkleman. / M.S.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 1990. / Includes bibliographical references (leaves 117-123). / by Michael Joseph Villalba. / Ph.D.

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 1997. / Includes bibliographical references (p. 107-110). / by Jose K. Menendez. / M.S.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 2012. / "June 2012." Cataloged from PDF version of thesis. / Includes bibliographical references (p. 205-212). / The beginning phases of system development and conceptual design require careful consideration, as these decisions will have significant influence on system lifetime performance and are often made with incomplete system knowledge. Decision makers may improve their capacity to discriminate between system concepts and design choices by measuring a system's "ilities" such as changeability, evolvability, and survivability. These ilities may enable systems to respond to perturbations in the design space, context space, and needs space in order to ensure system functionality and adequate performance over time. A system may be designed to change in response to perturbations, or remain statically robust/survivable to perturbations in order to avoid deficiencies or failures. This research attempts to analyze the mechanisms that allow system changes to occur. More specifically, this research will further the characterization of system changeability and evolvability and ultimately provide a structured and meaningful way of classifying system characteristics often described as "ilities". Value sustainment is proposed as an ultimate goal of systems, providing value in spite of perturbations in design, context, or needs. The premise of value sustainment is investigated through four distinct research thrusts: 1) a basis for defining system changes and ilities; 2) a system change examples database with categorical cluster analysis case research; 3) epoch-shift, impact, response, outcome case research; and 4) expert interviews case research. Focusing on change-related ilities, this research proposes constructs for identifying and enabling vague, yet desirable, system properties. Evolvability is characterized as a subset of changeability and defined as the ability of an architecture to be inherited and changed across generations [over time], with a set of ten proposed design principles including decentralization, redundancy, targeted modularity, scalability, integrability, reconfigurability, mimicry, leverage ancestry, disruptive architectural overhaul, and resourceful exaptation. / by Jay Clark Beesemyer, Jr. / S.M.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 2011. / Cataloged from PDF version of thesis. Vita. / Includes bibliographical references (p. 52-55). / Neck and back pain is one of the most common musculoskeletal complaints in personnel in variable acceleration environments such as astronauts and military pilots. Ultrasound is known for dynamic imaging and diagnostic workup of the axial and appendicular skeleton, but is not currently used to image the cervical spine, the injury of which may change the biomechanics of the cervical vertebrae, which CT and MRI (the current gold standard in cervical spine imaging) are poor at capturing. To validate ultrasound as a modality for imaging dynamic motion of the cervical spine several experiments were performed in static and dynamic human and animal (ovine) models: 1. Static analysis of ex-vivo ovine cervical spines imaged by ultrasound, MRI, and CT demonstrated that the imaging modality affected the measured intervertebral disc height (p<0.01); similar evaluation was done in-vivo in Emergency Department patients who received a CT scan as part of their clinical course that showed that ultrasound could fit into existing clinical workflows. 2. Dynamic analysis of isolated ex-vivo ovine cervical spinal segments intervertebral disc displacement with a mounted ultrasound probe demonstrated a measurement uncertainty of ± 0.2 mm and no bias at low frequency sinusoidal spinal displacement. A similar evaluation in-vivo with humans with an ultrasound probe mounted on a cervical-collar found a 0.8-1.3 mm amount of cervical spine distraction from the C4-5 Functional Spinal Unit. In human cadavers subjected to passive flexion and extension of the cervical spine, ultrasound measurements of the relative flexion/extension angles between consecutive cervical vertebrae were similar to fluoroscopy. 3. Ultrasound was able to record dynamic motion of the cervical spine in-vivo in running on a treadmill, during parabolic flight, and traveling over a rough road in a military vehicle. The ultrasound methods developed and tested in this thesis could provide an inexpensive, portable and safe technique that can identify and characterize cervical spine anatomy and pathology. / Funding Acknowledgment: National Space Biomedical Research Institute, Army Research Office, Children's Hospital Orthopedic Surgery Foundation / by Daniel Miller Buckland. / Ph.D.