Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 2000. / Includes bibliographical references (p. 177-186). / A novel new actuator for helicopter rotor control, the X-Frame Actuator, was developed, demonstrating superior performance for applications requiring compact, fast acting, large stroke actuation. The detailed experimental characterization of this actuator is described, including bench-top output energy measurements and transverse shake test performance. A Mach scaled rotor blade utilizing the X-Frame actuator to power a trailing edge servo-flap near the tip was also designed, manufactured and tested. A description of the design and composite manufacturing of the rotor blade and servo-flap is presented. Preliminary bench tests of the active blade actuation system are also presented. The hover tests of the active blade provided transfer function identification of the performance of the actuator in producing flap deflections, and the response of the rotor from deflections of the servo-flap. At the highest field level of 60 V/mil P-P the actuation system produces 7.75 degrees of quasi-static peak-to-peak flap deflection in hover. The servo-flap produces significant control authority, especially near the 3/rev frequency that would be important for the CH-47. Scaled to a full-sized CH-47, the rotor can produce over 16,000 lb peak-to-peak thrust variation at 3/rev, which is 32% of the aircraft's gross weight. Closed-loop feedback control was experimentally applied to the model rotor system. Both single frequency and combined frequency controllers were successfully implemented on the rotor. Most significantly, simultaneous control of 1/rev, 3/rev, 4/rev, 5/rev, and 6/rev harmonic vibration has been successfully demonstrated. The peak vibrations were eliminated at each frequency, as well as the vibrations over a small bandwidth surrounding each peak. Experimental comparison of continuous time versus discrete time control has shown the former to be a more effective approach for vibration reduction. / by Eric Blade Prechtl. / Ph.D.

Massachusetts Institute of Technology. Dept. of Aeronautics and Astronautics. Thesis. 1966. M.S. / Bibliography: leaf 42. / M.S.

Massachusetts Institute of Technology. Dept. of Aeronautics and Astronautics. Thesis. 1969. M.S. / MICROFICHE COPY ALSO AVAILABLE IN AERO LIBRARY. / Bibliography: leaf 61. / M.S.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, February 2004. / Includes bibliographical references (p. 215-222). / In order to maintain Air Traffic Control (ATC) system safety, security and efficiency, conformance monitoring must be performed to ensure that aircraft adhere to their assigned clearances. New Decision Support Tools (DSTs), coupled to advanced communication, navigation and surveillance technologies are being developed which may enable more effective conformance monitoring to be undertaken relative to today. However, there are currently no general analysis techniques to help identify fundamental conformance monitoring issues and more effective approaches that new DSTs should employ. An approach to address this need is presented in this work that draws parallels between ATC conformance monitoring and general system fault detection, allowing fault detection methods developed for other domains to be employed for this new application. The resulting Conformance Monitoring Analysis Framework provides a structure to research conformance monitoring issues and approaches. Detailed discussions are presented for each of the elements of the framework, including the Conformance Basis, Actual System Representation, Conformance Monitoring Model, Conformance Residual Generation and Decision-Making components. Flight test data during a simple lateral non-conformance maneuver was used to demonstrate various implementation options of the framework. Application of the framework for ATC conformance monitoring research was demonstrated using flight test and simulator data in various operational and surveillance environments. Key findings in the lateral, vertical and longitudinal domains during non-transitioning and transitioning flight regimes are presented. In general, it was found that more effective conformance monitoring can / (cont.) be conducted relative to existing systems in the non-transitioning environments when advanced surveillance systems provide higher accuracy, higher update rate and higher order dynamic state information for use in more sophisticated DST algorithms. This is contrasted to the significantly greater conformance monitoring challenges that exist in the transitioning regimes due to Conformance Basis and modeling uncertainties. These challenges can be handled through the use of procedural design, higher fidelity modeling techniques or the surveillance of intent states. Two extended applications of the framework are also presented: a method for intent inferencing to determine what alternative trajectory a non-conforming aircraft may be following and a technique for environmental parameter estimation. / by Tom George Reynolds. / Ph.D.

Massachusetts Institute of Technology. Dept. of Aeronautics and Astronautics. Thesis. 1970. M.S. / MICROFICHE COPY ALSO AVAILABLE IN AERO LIBRARY. / Bibliography: leaf 41. / M.S.

Thesis: S.M., Massachusetts Institute of Technology, Department of Aeronautics and Astronautics, 2014. / Cataloged from PDF version of thesis. / Includes bibliographical references (pages 135-136). / The unsteady pressure field experienced by a centrifugal compressor stage can be dominated by of the impeller-diffuser interaction. The energy of the unsteady field, under certain aerodynamic and structural conditions, is capable of forcing the rotating impeller blades to vibrate excessively to the point of failure, better known as a high cycle fatigue (HCF) failure. This thesis seeks to identify the physical mechanisms that set the forced response amplitude of an impeller due to the impeller-diffuser interaction. The centrifugal stage researched is comprised of a stationary discrete passage diffuser and an unshrouded rotating impeller with both main and splitter blades. The forced response of two splitter blade modes are computed for a variety of structural boundary conditions and unsteady loadings to elicit the driving physical mechanisms. The findings indicate that the forced response is enhanced when the excitation frequency matches a component's natural frequency, the characteristic wavelength of the unsteady loading matches that of the structural vibration mode, the resonance occurs at high speed, and when modal displacement exists at the impeller blade's trailing edge. The findings also suggest that modal coupling of blade and disk dominant modes leads to high sensitivity of the forced response to small variations in airfoil and disk backwall thickness. Identification of blade-disk couplings are described using a simplified SAFE (Singh's Advanced Frequency Evaluation) diagram. The forced response of taut strings, Bernoulli-Euler beams, and a two mass-spring system are also utilized to elicit how the physical mechanisms act on the impeller's forced response. The Bernoulli-Euler beam model suggests that a mismatch of the forcing wavelength to the structural wavelength by 50% will reduce the forced response amplitude by at least 75%. Finally, a decision tree is proposed to assess the relative resonant risk of impeller modes to the diffuser excitation by identifying which of the physical mechanisms may be the dominant driver of the forced response. / by Edward James Walton. / S.M.

Thesis: Ph. D., Massachusetts Institute of Technology, Department of Aeronautics and Astronautics, 2018. / Cataloged from PDF version of thesis. / Includes bibliographical references (pages 120-122). / Oil extraction on many reservoirs requires the use of rod pump systems to pump the fluid to the surface. A longstanding challenging issue in the operation of rod-pump system is the ability to determine the downhole pump conditions based on the knowledge of a finite set of measurables at the top. A novel acoustic-based diagnostic method is put forward as an enabler for determining the downhole conditions. It consists of reconstructing the pressure signal generated by the pump from an acoustic measurement made at the top. Knowing that the operating pump radiates pressure waves in the fluid, the pump operation can thus be monitored. The physical basis of this acoustic method is demonstrated using results from a model of the rod-pump system complemented by field data measured from representative operating oil wells. The rod pump model has shown to be in good accord with available data. The unique feature differentiating the model formulation from the state of art is that each of the model attributes is linked to the physical process that set the pump operation. The wave equations in the rod string and in the tubing are solved using a custom numerical scheme, and the coupling between the rod and the fluid surrounding it is taken into account. The field measurements and the model results are in accord as they prove the hypothesis that a surface measured pressure can be used to determine the downhole condition of the well. Likewise both the field measurements and the model results provide the physical basis for formulating the scaling rule for generic rod pump system which is used in turn to design a scaled down experimental setup. Specifically, the effect of gas on the pump acoustic signature has been characterized and this general scaling allow one to compare different wells to one another and to obtain a universal scaling parameter to measure the amount of gas in wells pumps. The anticipated technological impact on oil production infrastructure is an acoustic diagnostic framework for assessing a broad class of wells operation, from vertical to horizontal oil wells. / by Sébastien Karim Mannaï. / Ph. D.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 2007. / Includes bibliographical references (p. 216-244). / Fusion energy is attractive for use in future spacecraft because of improved fuel energy density and reduced radioactivity compared with fission power. Unfortunately, the most promising means of generating fusion power on the ground (Tokamak based reactors like ITER and inertial confinement reactors like NIF) require very large and heavy structures for power supplies and magnets, in the case of magnetic confinement, or capacitors and lasers in the case of inertial confinement. The mass of these reactors and support equipment is sufficiently large that no existing or planned heavy-lift vehicle could launch such a reactor, thereby necessitating in-space construction which would substantially increase the cost of the endeavor. The scaling of Inertial Electrostatic Confinement (IEC) is such that high power densities might be achievable in small, light-weight reactors, potentially enabling more rapid, lower cost development of fusion power and propulsion systems for space applications. The primary focus of the research into improving particle and energy confinement in IEC systems is based on the idea of electrostatic ion focusing in a spherically symmetric gridded IEC system. / (cont.) Improved ion confinement in this system is achieved by the insertion of multiple concentric grids with appropriately tailored potentials to focus ion beams away from the grid wires. In order to reduce the occurrence of charge exchange and streaming electron power losses, the system is run at high vacuum. This modification to the usual approach was conceived of by Dr. Ray Sedwick and computational modeling has been conducted by Tom McGuire using a variety of custom and commercial codes. In this thesis, a semi-analytic model of the potential structure around a multi-grid IEC device is developed. A 1-D paraxial ray ion beam envelope approximation is then used along an equatorial beamline and the assumed beam density is gradually increased until an effective beam space charge limit is reached at which point the potential fusion output is calculated. Significant use of the commercial particle-in-cell code OOPIC was made, and its ability to predict multi-grid IEC confinement properties is evaluated. An experiment was built to confirm the effectiveness of the multiple-grid structure to improve ion confinement times. It is shown that the multi-grid IEC can improve ion confinement time over the conventional, 2-grid IEC device. The PIC predicted ion bunching mode is also seen in experiment. / by Carl C. Dietrich. / Ph.D.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 2008. / Includes bibliographical references (p. 107-109). / Electric propulsion systems provide an attractive option for various spacecraft propulsion applications due to their high specific impulse. The power balance of an electric thruster based on a helicon plasma source is presented. The power balance is shown to be comprised of several variables, including the RF power supplied to the system, dissipative losses in transmission hardware, losses in the neutral confinement tube, uncoupled RF radiation, ionization power, and plume output power. A thermal model for the neutral confinement tube is presented whereby heat flux may be derived from thermal response data. Numerical simulation and experimental benchmarking are employed to validate this thermal model. A mapping of power consumption is presented. Comparison with experimental parameters indicates that 97% of the power supplied to the system is accounted for, suggesting that primary loss mechanisms have been identified. Avenues for improving the performance of the thruster, based on these data, are presented. / by Daniel B. White, Jr. / S.M.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 2003. / Includes bibliographical references (p. 89-90). / by Sebastien Aknouche. / S.M.