Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 2007. / Includes bibliographical references (p. 69-71). / This thesis demonstrates a technique that reduces the perceived error introduced in the visualization of higher-order DG solutions with traditional tools. Most visualization techniques work by using the solution at the mesh vertices and linearly interpolating to color the interior of the element. For higher-order solutions (where the visualization mesh is the same as the solution mesh) this method renders the high-order solution linear. By inserting new nodes at element quadrature points where the difference between the actual solution and the linear rendering is above a user-defined tolerance, additional elements are created and used for the visualization process. In order to keep the counts low for this new mesh, after each insertion a local rearrangement is performed to readapt the parent element so that the total visualization error is reduced. The method introduced here has many advantages over isotropic adaptation used by some higher-order visualization techniques. Isotropic adaptation adapts all the elements regardless of error, thus creating a higher total element count and therefore requiring more memory and rendering time. In some cases isotropic elements are not ideal in representing the solution (ie: boundary layers, shocks, wakes, etc.). Lastly, by providing an option to define the maximum visualization error allows the user to specify how close the visualized solution is to the actual calculated one (at the expense of a denser visualization mesh). Second, this work introduces a new method to apply an accuracy maintaining post-processor on DG vector fields to improve on the standard streamlining algorithms. Time integration methods do not work accurately and may even fail on discontinuos fields. The post-processor smoothens the field and eliminates the discontinuity between elements thus resulting in more accurate streamlines. To keep down the computational cost of the method, the post-processing is done in a one dimensional manner along the streamline. / by David Walfisch. / S.M.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 2010. / 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 (p. 60-61). / NASA is concerned with finding performance predictors for space teleoperation tasks in order to improve training efficiency. Experiment 1 determined whether scores on tests of spatial skills could predict performance when selecting camera views for a simulated teleoperation task. The hypothesis was that subjects with high spatial ability would perform camera selection tasks more quickly and accurately than those with lower spatial ability, as measured by the Mental Rotation Test (MRT), Purdue Spatial Visualization Test (PSVT), and the Perspective Taking Ability (PTA) test. Performance was defined by task time, number of correct camera selections, preparation time, number of camera changes, and correct identification of clearance issues. Mixed regression and nonparametric tests showed that high-scoring subjects on the MRT and PTA spatial ability tests had significantly lower task times, higher camera selection scores, and fewer camera changes than subjects with lower scores, while High PSVT scorers had significantly lower preparation times. Experiment 2 determined whether spatial ability, joystick configuration, and handedness influenced performance of telerobotic fly-to tasks in a virtual ISS environment. 11 righthanded and 9 left-handed subjects completed 48 total trials, split between two hand controller configurations. Performance was defined by task time, percentage of translational and rotational multi-axis movement, percentage of bimanual movement, and number of discrete movements. High scorers for the MRT, PSVT, and PTA tests had lower Task Times, and High PSVT and PTA scorers made fewer Discrete Movements than Low scorers. High MRT and PTA scorers had a higher percentage of translational and rotational multi-axis movement, and High MRT scorers had a higher percentage of bimanual movement. The overall learning effect appears to be greater than the effect of switching between hand controller configurations. No significant effect of handedness was found. These results indicate that these spatial ability tests could predict performance on space teleoperation tasks, at least in the early phases of training. This research was supported by the National Space Biomedical Research Institute through NASA NCC 9- 58. / by Teresa Maria Pontillo. / S.M.

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. 82-86). / Astronauts on the International Space Station must perform mission critical space telerobotics tasks consistently despite restricted and slam shifted sleep and circadian schedules and long session durations, which all potentially degrade cognitive function, response time, and attention. A ground laboratory experiment was designed to 1) Determine the effects of fatigue on performance metrics in simulated space telerobotics tasks, 2) Examine the relationships between performance on complex robotics tasks and traditional metrics of cognitive task performance and sleepiness, 3) Assess the efficacy of caffeine and blue light countermeasures, and 4) Evaluate individual subject vulnerability to fatigue. Subjects were screened for robotics aptitude, and trained on three robotics tasks and a mental workload assessing secondary task at MIT. After a week of 6-hr sleep restriction, they were admitted to the Brigham and Women's Hospital sleep laboratory, a time-cue free environment, and underwent a 13 day double blind protocol including physiologic monitoring and robotic and cognitive testing. Their sleep schedule was repeatedly slam shifted 9 hours earlier then they performed the robotics tasks under different countermeasure conditions. This thesis documents the protocol and details of the robotics training and testing, and includes a preliminary analysis of data from 16 subjects focusing on robotics and secondary task data. Since the study is continuing and investigators are blinded to countermeasure conditions, data from the countermeasure sessions is not included. Thesis goals were to 1) Analyze the predictive capability of spatial ability tests on individual robotics performance, 2) Evaluate the effects on robotics metrics of proxy measures of circadian and time-on-task, and 3) Assess individual differences in performance and vulnerability to fatigue. The Vandenberg Mental Rotation Test was found to be the best predictor of both robotics screening test and experimental performance, although an average of four spatial ability tests was slightly better for screening purposes. A comparison between a final training and non- countermeasure test session indicated that slam shifting had no significant effect on group average performance in any of the three robotics tasks or the secondary task. However, within the slam shifted session, a time-on-task related effect in secondary task performance was evident, suggesting that mental workload gradually increased even though subjects were able to maintain primary robotics task performance. Inter-subject differences were consistently larger than other effects. / by Raquel Galvan. / S.M.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 2008. / Includes bibliographical references (p. 117-120). / The terminal-area surrounding an airport is an important component of the air transportation system, and efficient and robust terminal-area schedules are essential for successfully meeting the projected increase in air traffic demand. Aircraft arrival schedules are subject to a variety of operational constraints, such as minimum separation requirements for safety, required arrival time-windows, limited deviation from a nominal or FCFS sequence, and precedence constraints on the arrival order. With these constraints, there is a range of desirable objectives associated with multiple stakeholders that could be optimized in these schedules. The schedules should also be robust against the uncertainty around the terminal-area. A dynamic programming algorithm for determining the minimum cost arrival schedule, given the aircraft-dependent delay costs, is presented in this thesis. The proposed approach makes it possible to determine various tradeoffs between multiple objectives in terminal-area operations. The comparison of schedules that maximize throughput to those that minimize average delay shows that the benefit from maximizing throughput could be at the expense of an increase in average delay, and that minimizing average delay is the more advantageous of the two objectives in most cases. A comprehensive analysis of the tradeoffs between throughput and fuel costs, and throughput and operating costs is conducted, accounting for both the cost of delay (as reported by the airlines) and the cost of speeding-up when possible (from models of aircraft performance). It is also demonstrated that the proposed aircraft scheduling algorithm can be applied to the optimization problem for the coupled operations of arrivals and departures on a single runway. / (cont.) Using the same framework, a dynamic programming algorithm for robust scheduling in terminal-area is also developed. This algorithm is designed to minimize the possibility that an air traffic controller has to intervene the initially determined schedule under the uncertainty of the landing time accuracy due to the aircraft equipage. The result from the proposed approach is a tradeoff curve between runway throughput and robustness. / by Hanbong Lee. / S.M.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 2004. / Includes bibliographical references (p. 86-87). / Recent developments in astronautical engineering have led to the adoption of low thrust rocket engines for spacecraft. Optimizing the orbital transfers for low thrust engines is significantly more complicated than optimizing transfers for impulsive engines because a continuous control law must be found and long integrations are necessary to determine whether the control law works or not. Previous work on optimizing low thrust orbital transfers has led to the development of control laws for continuous thrusting including the effects of oblateness, multiple attracting bodies, eclipses, and solar cell degradation. The current work adds to this by developing control laws for optimal coasting and for variable specific impulse at constant power. The Hamiltonian method is used to develop the optimal control laws and physical interpretations are given to each term in the Hamiltonian. Application of the optimal coasting control law to transfers from LEO to GEO indicate that small amounts of coasting can significantly reduce the fuel needed for a transfer. / by James K. Whiting. / S.M.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 2006. / Includes bibliographical references (p. 177-179). / The trajectory analysis and mission design for inspection of a host spacecraft by a microsatellite is motivated by the current developments in designing and building prototypes of a microsatellite inspector vehicle. Two different, mission scenarios are covered in this thesis - a host spacecraft in orbit about Earth and in deep space. Some of the key factors that affect the design of an inspection mission are presented and discussed. For the Earth orbiting case, the range of available trajectories - natural and forced - is analyzed using the solution to the Clohessy-Wiltshire (CW) differential equations. Utilizing the natural dynamics for inspection minimizes fuel costs, while still providing excellent opportunities to inspect and image the surface of the host spacecraft. The accessible natural motions are compiled to form a toolset, which may be employed in planning an inspection mission. A baseline mission concept for a microsatellite inspector is presented in this thesis. The mission is composed of four primary modes: deployment mode, global inspection mode, point inspection mode, and disposal mode. Some figures of merit that may be used to rate the success of the inspection mission are also presented. / (cont.) A simulation of the baseline mission concept for the Earth orbiting scenario is developed from the trajectory toolset. The hardware simulation is based on the current microinspector hardware developments at the Jet Propulsion Laboratory. Through the figures of merit, the quality of the inspection mission is shown to be excellent, when the natural dynamics are utilized for trajectory design. The baseline inspection mission is also extended to the deep space case. / by Susan C. Kim. / S.M.

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 1998. / Includes bibliographical references (leaves 187-190). / by Eric Benjamin Nelson. / M.S.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 2010. / 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 (p. 75-76). / We present a high-fidelity numerical study of a two-dimensional °apping airfoil, ad- dressing the hypothesis that boundary layer feedback control can enable improved performance in flapping light. To this end, we model a novel biologically-inspired feedback controller which adjusts wing motion in response to the flow-induced bending load experienced by sensory hairs mounted on the wing. Such hairs have been observed on bats, and biological studies suggest that an associated feedback controller may play an important role in enabling bats' well-known mastery of light. The coupled °uid and structural equations of our model are solved numerically by a Discontinuous Galerkin finite element method, combined with an Arbitrary Lagrangian-Eulerian (ALE) formulation to account for airfoil motion. Feedback control is deed by a simple proportional-derivative (PD) control law relating hair sensor feedback to an applied torque at the pivot point of the wing. We also include a torsional spring at the pivot point to model passive aeroelasticity, following prior work by Israeli [5]. Our results show that hair sensors are well-suited for detecting flow separation, and sensors placed near the leading edge enable better light performance than sensors placed near the trailing edge. We compute a "performance envelope" for a purely passive flapping airfoil, and demonstrate that our active feedback controller enables improvements of up to 5% in propulsive efficiency. We also present gust alleviation experiments, where we find that an optimal PD controller reduces lift deviation by 33% compared to a spring-only airfoil. Mechanisms for these performance improvements are discussed. Our findings suggest that boundary layer feedback control may plausibly contribute to the outstanding °ight abilities of bats, and may also provide valuable clues for designing robust and maneuverable Micro Air Vehicles (MAVs). / by Hemant Kumar Chaurasia. / S.M.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 2012. / This thesis was scanned as part of an electronic thesis pilot project. / Cataloged from PDF version of thesis. This thesis was scanned as part of an electronic thesis pilot project. / Includes bibliographical references (p. 157-165). / Numerical simulations of incompressible viscous flows in realistic configurations are increasingly important in many scientific and engineering fields. In Aeronautics, for instance, relatively cheap numerical computations replace costly hours of wind tunnel investigations in the early design stages of new aircraft. However, standard methods to obtain numerical solutions over complex geometries require sophisticated meshing techniques and intensive human interaction. In contrast, "immersed methods" incorporate complex boundaries and/or interfaces into regular meshes (Cartesian meshes or simple triangulations). Hence, immersed methods simplify the task of mesh generation and are of great interest in the study of incompressible viscous flows. The objective of this thesis is to advance current immersed methods by formulations that yield highly accurate discretizations without compromising computational efficiency. This is achieved by introducing a new type of immersed method, the correction function method. This new method is based on the concept of a correction function that provides smooth extensions of the solution across boundaries and/or interfaces, such that standard (accurate and efficient) discretizations of the governing equations remain valid everywhere in the computational domain. Furthermore, the key concept behind the correction function method is the introduction of the correction functions as solutions to partial differential equations, which are defined locally around the immersed boundaries and interfaces. Then, we can solve these equations to any desired order of accuracy, resulting in high accuracy methods. Specifically, in this thesis the correction function method is implemented to 4th order of accuracy in the context of Poisson's equation, the heat equation, and the nonlinear convection advection diffusion in 2D. Then, these techniques are combined to solve the incompressible Navier-Stokes equations, which govern the dynamics of incompressible viscous flows. / by Alexandre Noll Marques. / Ph.D.

Thesis: Ph. D., Massachusetts Institute of Technology, Department of Aeronautics and Astronautics, 2014. / Cataloged from PDF version of thesis. / Includes bibliographical references (pages 193-210). / Planetary exploration missions are becoming increasingly complex and expensive due to ever more ambitious scientific and technical goals. On the other hand, budgets in planetary science have suffered from dramatic cuts over the past decade and projections estimate a flat budget of approximately $1.2B/year for the upcoming years. This has led to a desire for a reduction in the risk and complexity, as well as an increase in the robustness and reliability, of planetary exploration vehicles. One of the methods proposed to deal with this issue is the use of distributed, multi-vehicle architectures as a replacement for the traditional large, monolithic systems used in flagship missions. However, mission concept formulation engineers do not possess the tools to include multi-vehicle architectures in their early trade space exploration process. This is mostly due to the fact that these types of architectures cannot be readily evaluated against monolithic systems through the use of traditional mass-based metrics. Furthermore, in multi-vehicle system, architectural decisions about one vehicle, such as instrument or capability selection, quickly propagate through the entire system and impose requirements on the other vehicles. This can be difficult to model without going through detailed point designs. The objective of this thesis is to explore the potential benefits of both spatially and temporally distributed multi-vehicle systems, where the vehicles are heterogeneous, as compared to monolithic systems. Specifically, a set of metrics mapping the effects of using multi-vehicle systems on science benefit, complexity, mass, cost, coverage, productivity and risk are developed. Furthermore, a software tool to simulate the performance of teams of planetary surface vehicles in their operational environment has been built and its use demonstrated. Finally, the framework put forward in this thesis is used to perform several case studies, including a case study on the exploration of the Jovian moon Europa and another on the ascent and return components of a Mars Sample Return mission. From these, distributed systems are shown to provide increased science return and robustness as well as lower development and manufacturing costs as compared to their monolithic equivalents. / by Farah Alibay. / Ph. D.