Thesis: S.M., Massachusetts Institute of Technology, Department of Aeronautics and Astronautics, 2016. / Cataloged from PDF version of thesis. / Includes bibliographical references (pages 131-133). / The Hybrid Shell Model (HSM) is presented as an intermediate-fidelity structural model well suited for conceptual design of aerospace vehicles. Although significantly simpler and more economical than full 3D elasticity models, it can still capture full 3D geometries, large deformations, and anisotropic materials. HSM is formulated from the full 3D equilibrium and compatibility equations all projected onto local bases defined on the 2D shell manifold. General anisotropic constitutive equations are also formulated in the local 2D shell manifold bases. The resulting continuous HSM formulation is discretized in weak form with a Galerkin finite element method (FEM), with spherical interpolation used for the local basis vectors. Displacements, basis rotations, and stress resultants are the primary unknowns. A fully adjoint-consistent plane-stress HSM version (HSM2D) is developed for the purpose of model verification and demonstration of order-of-accuracy convergence. The Method of Exact Solutions (MES) is applied to the case of a uniform plate hanging under its own weight. The effectiveness of the adjoint model for structural optimization is also demonstrated for a simplified rotor blade in a centrifugal force field, featuring non-uniform forcing, non-zero Poisson ratio, large deflection, and optimization of multiple parameters. The suitability of HSM as an intermediate fidelity conceptual aircraft design tool is thus demonstrated. / by William Cooper Thalheimer. / S.M.

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 1994. / Title as it appears in the June 1994 MIT Graduate List: Rotational effects of turbine cooling. / Includes bibliographical references (leaves 102-103). / by Pamela S. Barry. / M.S.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 2004. / This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections. / "September 2004." / Includes bibliographical references (p. 73-75). / (cont.) The last experiment showed that individual subjects PER values changed over time intervals as short as ten minutes, and revealed the importance of the subject's prior experience in PER experiments. This suggests that limitations of working memory may effect the repeatability of the PER measure. The definition and measure of PER for each subject may also provide a means for quantifying the magnitude of a clinical condition known as oscillopsia, where we perceive the world as non-stationary, such as moving independently of our head motions. These findings are important for a perceptually sensitive environment, such as virtual reality. Designers of virtual environments that utilize self-motion perception should consider calibrating PERs within a session for each individual user and be aware that that the subject's calibration may change over time. / If we walk on a treadmill and are looking in the direction of motion of a moving virtual environment, the perceptions from our various senses are harmonious only if the visual scene is moving in a narrow range of speeds that are, typically, greater than our walking speed. This observation has been reported when we project a virtual environment through a display with a restricted field-of-view, such as a head-mounted display (HMD). When the subject feels that the scene-motion is natural for their walking speed, the ratio of the speed of his visual surround to that of the treadmill walking speed is defined as his perceptual equivalence ratio (PER) in that setting. Four experiments explored a set of conditions under which the PER measured on a treadmill is constant. The experiments, motivated by several hypotheses, investigated the relationship between PER and display type (HMD vs. either desktop monitor or on-screen projection), sense of presence in the virtual environment, and the magnitude of illusory self-motion (vection). We also investigated differences among subjects, and the stability of PER over time due to the limitations of working memory. Most experiments considered more than one hypothesis. The first two experiments found that PER was affected by the type of display used, but found no correlation of PER with the sense of presence reported by the subject. A third experiment showed that PER was nearly the same whether we manipulated visual or treadmill speed (and asked the subject to match the other.) While PER values were often constant versus treadmill speed for any individual subject, they were very different from subject to subject. PER appears to be relatively stable over a short test session, but may be highly variable over extended periods of time. / by Kevin R. Duda. / S.M.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 2005. / Includes bibliographical references (p. 111-112). / A unique counter-rotating aspirated compressor was tested in a blowdown facility at the Gas Turbine Laboratory at MIT. The facility expanded on experience from previous blowdown turbine and blowdown compressor experiments. Advances in thermocouple and facility designs enabled efficiency estimates through total temperature and total pressure measurements. The facility was designed to provide at least 100 ms of available test time, approximately a factor of five greater than previous blowdown compressor facilities. The adiabatic core efficiency of the compressor was estimated with an uncertainty of 0.8% and the corrected flow was estimated with an uncertainty of 1.0%. The compressor was tested at several operating conditions and two speed lines were partially mapped. The maximum measured total pressure ratio across the two stages was 3.02 to 1. The measured adiabatic efficiency for that point was 0.885. The span-wise total pressure, total temperature, and efficiency profiles were compared to the predicted profiles for runs with the corrected speeds of the two rotors at 90% of design and 100% design. There appears to be reasonable agreement between the predictions and the measurements. / by David V. Parker. / S.M.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 2006. / This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections. / Includes bibliographical references (p. 185-201). / Carbon nanotubes' (CNTs) superlative combination of electrical, thermal, and especially mechanical properties make them ideal candidates for composite reinforcement. Nanocomposites and hybrid composite architectures employing traditional advanced composites and CNTs offer significant potential mechanical and multifunctional performance benefits. CNT/polymer composites and two different hybrid architectures are experimentally investigated in this work. A novel process for rapidly growing dense, long, high-quality aligned CNT forests is employed. The first architecture is comprised of aligned fibers with CNTs grown radially on their surface. For the second architecture, dense forests of vertically aligned CNTs are placed between the plies of a laminate, in the through-thickness direction. Fundamental issues related to realizing hybrid composite architectures are investigated experimentally: wetting of the CNTs by commercially available polymers for the different architectures, effective reinforcement of the polymer matrices due to the addition of CNTs, and retention of mechanical (stiffness and strength) properties of the fibers after the CNT growth process. / (cont.) Wetting of CNT forests by several commercial polymers (including a highly-viscous epoxy) is demonstrated at rates conducive to creating a fully-dispersed CNT/matrix region for the two hybrid architectures previously described. Direct measurements of the mechanical properties of nanocomposites are reported for the first time in the literature. Increases in the Young's modulus of the polymer as high as 220% with just 2% volume fraction of aligned CNTs are observed. Equivalent reinforcement had been obtained previously by other authors with 5% volume fraction of randomly oriented CNTs. Single-fiber tension tests indicate no mechanical degradation (stiffness and strength) for alumina fibers undergoing the CNT growth process. Preliminary results on the fabrication of the two hybrid architectures are also presented. All the experimental results presented in this work indicate that hybrid CNT/composite architectures are feasible and future work focuses on mechanical and multifunctional property characterization of these and other hybrid architectures, and scaling to a continuous CNT growth process. / by Enrique J. García. / S.M.

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 1991. / Includes bibliographical references (leaves 127-128). / by Kurt D. Eberly. / M.S.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 1997. / Includes bibliographical references (leaves 152-154). / by Duncan P. Reijnen. / Ph.D.

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 1995. / by Kevin Sung-ho Lee. / M.S.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 1991. / Includes bibliographical references (p. 145-150). / by Petros G. Voulgaris. / Ph.D.

Thesis: S.M., Massachusetts Institute of Technology, Department of Aeronautics and Astronautics, 2015. / Cataloged from PDF version of thesis. / Includes bibliographical references (pages 133-135). / This thesis describes experimental assessments of the aerodynamic boundary layer ingestion (BLI) benefit of the D8 advanced civil aircraft design. Two independent methods were applied for 1:11 scale (4.1 m wingspan) powered aircraft model experiments in the NASA Langley 14x22-foot Subsonic Wind Tunnel. The metric used as a surrogate for fuel consumption was the input mechanical flow power, and the benefit was quantified by back-to-back comparison of non-BLI (podded) and BLI (integrated) configurations. The first method (indirect) was the estimate of mechanical flow power based on the measured electrical power to the propulsors, plus supporting experiments to characterize the efficiencies of the fans and the electric motors that drive them, at the MIT Gas Turbine Laboratory. The second method (direct) was the direct integration of flowfield measurements, from five-hole probe surveys at the inlet and exit of the propulsors, which provided flow angles, velocity components, and pressure coefficients. Data were taken at different wind tunnel speeds, and conditions to determine overall performance dependence on non-dimensional power and angle of attack. At the simulated cruise point, the first method gave a measured aerodynamic BLI benefit of 7.9% +/- 1.5% at 70 mph tunnel velocity, and 8.5% +/- 1.5% at 84 mph, and the second method gave a measured benefit of 8.1% +/- 3.3% at 70 mph, and 12.2% +/- 3.4% at 84 mph. For the aircraft models examined, the aerodynamic benefit was found to come primarily from a decrease in the propulsor jet velocity (increase in propulsive efficiency) and thus a decreased jet dissipation, with the contribution from decreased wake and airframe dissipation being roughly an order of magnitude smaller. / by Cécile J. Casses. / S.M.