The Dynamic Positioning (DP) System is responsible for the station keeping of vessels in several offshore operations. The forces required by the DP System are distributed among the available thrusters by a thrust allocation algorithm which should be accurate, efficient and robust. This means that the effective forces match the required forces while power consumption is minimized. Additionally, in case of impossibility of generating the required forces the heading of the vessel is maintained to avoid increasing environmental forces. To accurately generate the required forces, the physical limitations of the thrusters and the hydrodynamic interactions must be considered. The hydrodynamic interactions are consistently modelled to accommodate the following typical effects: thruster-hull, thruster-current and thruster-thruster interaction. The result of this modeling is a nonlinear optimization problem, which is solved using the Sequential Quadratic Programming (SQP) algorithm with slack variables. The DP simulation carried out show that by considering the hydrodynamic interactions on thrust allocation the overall performance (controllability and power consumption) of the DP system is improved. / O Sistema de Posicionamento Dinâmico (DP) é responsável pela manutenção da posição de embarcações em diversas operações offshore. As forças requeridas pelo Sistema DP são distribuídas entre os propulsores disponíveis por um algoritmo de alocação de empuxo que deve ser preciso, eficiente e robusto. Isso significa que as forças efetivas correspondem às forças solicitadas, enquanto o consumo de energia é minimizado. Além disso, em caso de impossibilidade de gerar as forças necessárias, o rumo da embarcação é mantido para evitar o aumento das forças ambientais. Para gerar com precisão as forças necessárias, as limitações físicas dos propulsores e as interações hidrodinâmicas devem ser consideradas. As interações hidrodinâmicas são modeladas de forma consistente para acomodar os seguintes efeitos típicos: interação entre casco e propulsor, correnteza e propulsor e entre propulsores. O resultado desta modelagem é um problema de otimização não linear, que é resolvido usando o algoritmo de Programação Quadrática Sequencial (SQP) com variáveis de relaxamento. As simulações de posicionameto dinâmico realizadas mostram que, ao considerar as interações hidrodinâmicas na alocação de empuxo, o desempenho geral (controlabilidade e consumo de energia) do sistema DP melhora.

The work presented here is a continuation of Spacecraft Trajectory Optimization Suite (STOpS), a master’s thesis written by Timothy Fitzgerald at California Polytechnic State University, San Luis Obispo. Low-thrust spacecraft engines are becoming much more common due to their high efficiency, especially for interplanetary trajectories. The version of STOpS presented here optimizes low-thrust trajectories using the Island Model Paradigm with three stochastic evolutionary algorithms: the genetic algorithm, differential evolution, and particle swarm optimization. While the algorithms used here were designed for the original STOpS, they were modified for this work. The low-thrust STOpS was successfully validated with two trajectory problems and their known near-optimal solutions. The first verification case was a constant-thrust, variable-time Earth orbit to Mars orbit transfer where the thrust was 3.787 Newtons and the time was approximately 195 days. The second verification case was a variable-thrust, constant-time Earth orbit to Mercury orbit transfer with the thrust coming from a solar electric propulsion model equation and the time being 355 days. Low-thrust STOpS found similar near-optimal solutions in each case. The final result of this work is a versatile MATLAB tool for optimizing low-thrust interplanetary trajectories.

The objective of this Master’s thesis is to find shape optimal design based on min- imizing friction force of thrust bearing by using genetic algorithm(GA) which is one of an optimization toolbox in Matlab. Reducing the friction force of thrust bearing is one way of making shaft to decreasing friction losses. With four parameters of thrust bearing geometry number of segments(m), angle of running surface(), segment inner radius(R0), and segment outer radius(R1) substitute in Reynolds’ equation. In order to know friction force, it is necessary to generate a connecting variable, oil film thickness(h0) from loading capacity(W ) and revolution per minute(rpm). Friction power loss, as well as weight func- tion conclude the final shape optimization of thrust bearing: m = 7, = 0.1, R0 = 15 mm, and R1 = 20 mm.

Applying the anisotropy of magnetic susceptibility to analogue models provides detailed insights into the strain distribution and quantification of deformation within contractional tectonic settings like fold-and-thrust belts (FTBs). Shortening in FTBs is accommodated by layer-parallel shortening, folding, and thrusting. The models in this research reflect the different deformation processes and the resulting magnetic fabric can be attributed to thrusting, folding and layer-parallel shortening. Thrusting develops a magnetic foliation parallel to the thrust surface, whereas folding and penetrative strain develop a magnetic lineation perpendicular to the shorting direction but parallel to the bedding. These fabric types can be observed in the first model of this study, which simulated a FTB shortened above two adjacent décollements with different frictional properties. The different friction coefficients along the décollements have not only an effect on the geometric and kinematic evolution of a FTB, but also on the strain distribution and magnitude of strain within the belt.  The second series of models performed in this study show the development of a thrust imbricate and the strain distribution across a single imbricate in more detail. Three models, with similar setup but different magnitudes of bulk shortening, show strain gradients by gradual changes in principal axes orientations and decrease in degree of anisotropy with decreasing distance to thrusts and kinkzones. These models show that at the beginning of shortening, strain is accommodated mainly by penetrative strain. With further shortening, formation of thrusts and kinkzones overprint the magnetic fabric locally and the degree of anisotropy is decreasing within the deformation zones. At thrusts, an overprint of the magnetic fabric prior deformation towards a magnetic foliation parallel to the thrust surfaces can be observed. A rather complex interplay between thrusting and folding can be analysed in the kinkzones. In general, this thesis outlines the characteristics of magnetic fabric observed in FTBs, relates different types of magnetic fabric to different processes of deformation and provides insights into the strain distribution of FTBs.

This master´s thesis solves the problem of stationary viscous flow of incompressible fluids in thin layers of fluid film lubrication in fixed pad thrust bearings. The parametric computational model of oil domain was created for investigation the distribution of pressure, velocity and thermal fields together with the determination of the basic parameters as axial force, heating up and friction loss. Subsequently this model was applied for investigation influence of uneven bearing clearance. The problem task was solved by final volume method in Ansys CFX 12.0 software.

Pulse Detonation Engines (PDEs) are propulsion systems that use repeated detonations to generate thrust. Currently in early stages of development, PDEs have been theorised to have advantages over current deflagration based engines. Air-breathing PDEs could attain higher specific impulse values and operate at higher Mach numbers than today's air-breathing engines, while Pulse Detonation Rocket Engines (PDREs) could become a lighter, cheaper, and more reliable alternative to traditional rocket engines. There are still however, many technological hurdles to overcome before PDEs can be developed into practical propulsion systems, one major barrier being management of their immense heat loads. This thesis outlines the development of a numerical model for determining thrust performance and heat load characteristics of PDEs. The model is based on a set of analytical equations which characterise the gas dynamics inside the engine throughout it's cyclic process. Being numerically light -when compared to CFD analysis- the model allows for fast turnaround of results and the ability to sweep through parameters to determine optimum operating conditions to maximise engine performance and reduce heat load. In this study, the working principles of the model are described and it's outputs are validated against data from published experimental and numerical studies. The model is then used to conduct a comprehensive parametric study on the effects of various reactant combinations, operating conditions, and engine geometries on engine thrust, specific impulse and heat load. Lastly, a brief study is conducted on the feasibility of regenerative cooling for PDEs, using model outputs to determine if a heat balance can be achieved and the performance losses and complications that would result.

While the interest in the Martian moons increases, the low-thrust propulsion technology is expected to enable novel mission scenarios but is associated with unique trajectory design challenges. Accordingly, the current investigation introduces a multi-phase low-thrust design framework. The trajectory of a potential spacecraft that departs from the Earth vicinity to reach both of the Martian moons, is divided into four phases. To describe the motion of the spacecraft under the influence of gravitational bodies, the two-body problem (2BP) and the Circular-Restricted Three Body Problem (CR3BP) are employed as lower-fidelity models, from which the results are validated in a higher-fidelity ephemeris model. For the computation and optimization of low-thrust trajectories, direct collocation algorithm is introduced. Utilizing the dynamical models and the numerical scheme, the low-thrust trajectory design challenge associated each phase is located and tackled separately. For the heliocentric leg, multiple optimal control problems are formulated between the planets in heliocentric space over different departure and arrival epochs. A contour plot is then generated to illustrate the trade-off between the propellant consumption and the time of flight. For the tour of the Martian moons, the science orbits for both moons are defined. Then, a new algorithm that interfaces the Q-law guidance scheme and direct collocation algorithm is introduced to generate low-thrust transfer trajectories between the science orbits. Finally, an end-to-end trajectory is produced by merging the piece-wise solutions from each phase. The validity of the introduced multi-phase formulation is confirmed by converging the trajectories in a higher-fidelity ephemeris model.<br>

Recent advancements in electric propulsion systems have made electric vertical takeoff and landing aircraft a reality, and one that is seen as a partial solution to the growing issue of urban traffic congestion. Designing an aircraft with multiple smaller motors and rotors spread across the wings–referred to as distributed electric propulsion (DEP)–has shown great potential in help- ing improve electric aircraft performance by offering increased propulsive efficiency, augmented lift, and structural load distribution. For these reasons, DEP is one configuration that is currently being implemented into multiple prototype designs (e.g. NASA’s Maxwell X-57, Airbus Vahana, Opener BlackFly, and Joby S2). However, while a DEP configuration has many potential benefits, it complicates the aerodynamics by introducing complex rotor-on-rotor interactions which can significantly affect noise generation. In this study we use unsteady Reynolds-averaged Navier–Stokes (RANS) simulations (STAR-CCM+) with an aeroacoustic solver (PSU-WOPWOP) to quantify thrust fluctuations and noise generation for two distinct rotor-rotor configurations. The configurations investigated in this study are: 1) coplanar rotors with a varying tip separation distance and 2) one rotor downstream of the other at varying distances for a fixed tip separation distance. Both configurations are investigated using an APC 10x7E and DJI-based 0.24 m rotor. It was found that tip-to-tip separation distance has a stronger influence on noise generation than the downstream separation distance does. A one diameter change in tip separation distance resulted in a ∼15 dBA change in noise while a three diameter change in downstream separation distance only resulted in a ∼9 dBA change in noise for the same rotor. Changes in thrust fluctuations were found to predict trends in noise generation well for multi-rotor configurations. Additionally, it was shown that when rotors are located less than 10% of the diameter apart from each other, noise can be decreased by up to 9 dBA by moving one rotor ∼0.5 diameter downstream of the other.

Tradition spacecraft proximity operations require large and expensive on-board sensors and significant ground support. Relative angle measurements can be obtained from small, simple, and inexpensive on-board sensors, but have not traditionally been used for proximity operation because of difficulty generating rang information. In this thesis it is shown that useful relative range data can be generated provided that the spacecraft is experiencing a small continuous thrust such as would be provided by a low-thrust propulsion system.

The downstructure of viewing geologic maps, balanced and cross sections, and hanging-wall-sequence diagrams are applied to produce the first comprehensive synthesis of the structure below the willard thrust sheet. Development of the duplex beneath the Willard thrust may be explained with a "piggyback" thrust model where younger thrust slices form below and fold an older, overlying thrust sheet. Progressive failure of the footwall ramp of the Willard thrust sheet extended the sole thrust eastward and produced a duplex consisting of thrust slices (horses) which adhered to the overriding thrust sheet where it ramped from a lower sole thrust to an upper decollement horizon. The resulting structural culmination produced a distinct antiform in the Willard thrust sheet. The duplex is here named the Ogden duplex. Frontal folds (formed at ramps perpendicular to transport) and lateral folds (formed at ramps parallel to transport) mark the margin of Individual horses within the duplex. Folded thrusts, thrust-splay relationships, and lateral overlap of horses help determine the sequence of thrusting. The involvement of cratonic foreland basement rocks (Farmington Canyon Complex) in thrust slices within the Ogden duplex is similar to the Moine thrust belt in northern Scotland and pinpoints this area within zone III of Boyer and Elliott's (1982) model of a thrust system dominated by a major thrust sheet. The basement rocks form the core of several horses which moved a minimum of 9.6 km. Total shortening within the Ogden duplex is estimated at 8 to 12 km. The sequence of thrusting is proposed from higher to lower: the willard thrust fault moved first, then the Ogden thrust fault and, finally, the Taylor and Weber thrust system (here named). Striking similarities between the Ogden thrust fault, the Weber-Taylor thrust system, and the Durst thrust fault geometries suggest that they are all part of the same system.