Thesis: S.M., Massachusetts Institute of Technology, Department of Aeronautics and Astronautics, 2013. / Cataloged from PDF version of thesis. / Includes bibliographical references (pages 59-60). / This thesis describes the construction of an automated gradient-based optimization process using the adjoint method and its application to centrifugal compressor return channel loss reduction. A proper objective function definition and a generalized geometry parametrization and manipulation algorithm were developed, and the appropriate adjoint equations and boundary conditions were derived for internal flow of an axisymmetric incompressible laminar flow. The adjoint-based gradient calculation was then validated against finite-difference calculations and embedded in a quasi- Newton optimization algorithm. An optimal design was proposed, which achieved an approximately 5% performance improvement compared to the baseline design in an incompressible laminar flow. The geometry was assessed in a compressible turbulent flow at the actual Mach number and Reynolds number and found to yield a 11% performance improvement for an axisymmetric channel with a previously optimized geometry. / by Wei Guo. / S.M.

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 1984. / Microfiche copy available in Archives and Barker. / Includes bibliographical references. / by Dale Gordon Stuart. / M.S.

Thesis: S.M., Massachusetts Institute of Technology, Department of Aeronautics and Astronautics, 2016. / Cataloged from PDF version of thesis. / Includes bibliographical references (pages 83-85). / As humanity prepares to break the bonds of Earth's orbit and send explorers deeper into the solar system, mission duration will drastically increase; forcing crewmembers to retain skills and knowledge from prior training on Earth for unprecedented lengths of time. Since performance generally diminishes when a skill is unused, the development of efficient and effective refresher training is essential. The effectiveness of training presumably can be increased by taking into account the learning style of the student and customizing training or retraining material. To understand the effect of customized retraining material on skill reacquisition, we compared space telerobotics performance post training and six months later using two refresher training regimens: written refresher material and personally customized refresher videos. Videos were created by the subjects after training was completed. We used a simulator of the ISS Robotic Arm as a complex task, which requires intricate bi-manual control as well as adherence to complex procedures. We compared performance change between the two retraining styles using subjective instructor evaluation as well as quantitative performance metrics. We assessed each subject's Felder-Silverman Index of Learning Style (ILS), and developed an analogous rubric to assess the teaching style of the refresher videos. We found weak correlations between learning and teaching metrics in 2/4 dimensions. We also found metrics of a subject's spatial abilities (MRT and PTA, with p-values <0.005) predicted performance and retention in procedurally complex tasks. Spatial ability had more effect on the control group's retention than those who received customized retraining. Results of this study will be used to inform NASA on the appropriate refresher materials for long-duration spaceflight crews. / by Lynn Marie Geiger. / S.M.

Thesis: S.M., Massachusetts Institute of Technology, Department of Aeronautics and Astronautics, 2017. / Cataloged from PDF version of thesis. / Includes bibliographical references (pages 91-92). / This thesis explores a variety of materials and methods for creating emitter arrays for the ion electrospray propulsion system (iEPS), a compact, efficient, and scalable space propulsion system for use in a wide range of space missions. The increasing utilization of small, cheap, easy-to-launch satellites known as CubeSats has spurred demand for a propulsion system which exists at the nexus of high power efficiency, low mass, surface area, and volume, and high specific impulse. iEPS has demonstrated a unique potential to satisfy all of these stringent design requirements in a way no presently existing propulsion system can. The first part of this work explores utilizing microelectromechanical systems (MEMS) processing to increase the thrust density of iEPS. Silicon molds were designed and manufactured with differing emission site size and spacing. Additionally, a variety of materials were tested with the aim of forming a porous network within the molds prior to selective removal of the mold. A molded array is successfully fired as a result of these research efforts. The second part of this work explores creation of porous substrates for use with an existing laser ablation method of creating emitter arrays. The first iEPS thrusters tested in space used porous borosilicate glass emitter chips, which demonstrated shortcomings in terms of material uniformity, pore size, and ionic liquid fuel containment. This work explores materials and methods for improving all of these and demonstrates the successful firing of an array made by sintering a silicon dioxide nano-bead powder. / by Alexander Connor Larkin Bost. / S.M.

Thesis: S.M., Massachusetts Institute of Technology, Department of Aeronautics and Astronautics, 2018. / Cataloged from PDF version of thesis. / Includes bibliographical references (pages 81-85). / This thesis presents a multi-fidelity methodology to enable the incorporation of high-fidelity data into a conceptual design process. The methodology is based upon a fidelity weighted combination of Gaussian Process surrogate models that takes into account both the quality of the Gaussian Process approximation and the confidence of the designer in the disciplinary model being approximated. The methodology is demonstrated on the stability and control analysis of a Blended-Wing-Body aircraft's center of gravity limits. The results show that low-fidelity data is enhanced by the presence of high-fidelity data in key areas of the design space. At the same time, the presence of even sparse high-fidelity data is key to reducing the variance in the stability and control analysis, thereby improving the quality of the predictions of the center of gravity limits. / by Alexander W. Feldstein. / S.M.

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 1995. / Includes bibliographical references (p. 109-111). / by Masahiko Kuzume Ikuta. / M.S.

Thesis: S.M., Massachusetts Institute of Technology, Department of Aeronautics and Astronautics, 2016. / Cataloged from PDF version of thesis. / Includes bibliographical references (pages 111-112). / This thesis analyzes the effects of two algorithms that control the departure of aircraft at congested airports, with an emphasis on the uncertainty of the underlying processes. These algorithms, N-control and dynamic programming, belong to a broader class of control policies called Pushback Rate Control (PRC) policies that calculate a pushback rate for departing aircraft based on the state of the airport surface congestion. During times of congestion, these algorithms limit the amount of aircraft on the airport surface while maintaining departure throughput. This reduces the taxi-out time of aircraft, resulting in reduced fuel burn and emissions. This thesis introduces the policies and simulates their performance at LaGuardia Airport while varying two policy parameters, the length of the prediction interval and the number of prediction intervals, under several types of uncertainty, including the departure schedule and arrival rate. As will be shown, each policy results in significant taxi-out time reductions, saving airlines at least 60,000 minutes of taxiing over a 2-month period with the traditional 15-minute time window simulations. However, when accounting for the uncertainty in the algorithm inputs or the variation of policy parameters, the performance of both PRC policies degrades. By accounting for the variation of policy parameters and the different sources of uncertainty that affect airport surface management, the main contribution of this thesis provides a realistic analysis of PRC policies. / by Patrick Kough McFarlane. / S.M.

Thesis: S.M., Massachusetts Institute of Technology, Department of Aeronautics and Astronautics, 2015. / Cataloged from PDF version of thesis. / Includes bibliographical references (pages 93-97). / Electrohydrodynamic (EHD) thrusters utilize ion neutral collisions in air to produce a propulsive force. The ions are generated at an emitting electrode in an asymmetric capacitor by a corona discharge. This thesis presents a Hybridized Discontinuous Galerkin (HDG) formulation for solving the EHD thruster governing equations with the exception of fluid flow equations. The problem is two-way coupled and non-linear. A smoothed charge injection model from the literature for the corona discharge is included in the HDG scheme. The formulation is validated against a model problem which has an analytical solution and parallel wire single stage and dual stage thruster performance data from the literature. The model problem consists of concentric cylinders with charge density and potential specified on the inner and outer cylinders. The inner cylinder is offset to test the charge injection boundary condition in an asymmetric solution. The single stage thruster consists of two parallel wires of different diameters separated by a 1 cm gap. The dual stage thruster consists of three inline parallel wires of different diameters separated by 1 cm and 3 cm. The HDG solution for the model problem is found to produce normalized errors on the order of 10-3 for the potential and charge density solutions. The charge density applied to the inner emitter electrode is increased over several solution iterations to resolve high charge density gradients. The charge density boundary condition applied to the offset case represented the expected qualities of a corona discharge. The smoothed boundary condition is shown to be tunable to allow for a trade-off between accuracy and numerical stability. The single stage thruster model replicated experimental thrust results within 14% error using homogeneous charge injection and the smoothed charge injection model requires a less stable setting to achieve similar accuracy. The dual stage model shows the necessity of a mixed outflow boundary condition to avoid non-unique solutions. / by Andrew Dexter. / S.M.

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 1991. / Includes bibliographical references (p. 93-94). / by Jesse Ross Gossner. / M.S.

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 1992. / Includes bibliographical references (leaves 136-143). / by Andrew D. Rothstein. / M.S.