This research seeks to increase the applicable range and sensitivity of Triple Langmuir Probes (TLPs) and Retarding Potential Analyzers (RPAs) in the characterization of sub-centimeter scale, unsteady plasmas found in micropropulsion and other non-propulsive applications. The validation of these plasma diagnostics is accomplished by their implementation in the plume of a Micro Liquid-fed Pulsed Thruster (MiLiPulT) prototype developed and MEMS fabricated by the Johns Hopkins University Applied Physics Laboratory. A current-mode TLP (CM-TLP) theory of operation for the thin-sheath and the transitional regimes is expanded to include the Orbital Motion Limited regime applicable to low density plasmas. An optimized CM-TLP bias circuit employing operational amplifiers in both a differential amplifier configuration as well as a voltage follower configuration has been developed to adequately amplify current signals in instances where traditional current measuring techniques are no longer valid. This research also encompasses novel sub-microampere signal amplification in the presence of substantial common-mode noise as well as several a priori electromagnetic interference elimination and filtering techniques. The CM-TLP wires used in the experiments were designed with a radius of 37.5 micron and a length of 5 mm. Measurements were taken in the plume of the MiLiPulT at 2.0 cm, 6.0 cm and 10.0 cm downstream of the exit using a linear translation stage. Reduced electron temperature and electron number density profiles for a set of filtered CM-TLP raw currents are presented. The results indicate increased accuracy due to successful amplification of CM-TLP current signals at the risk of op-amp saturation due to inherent electrical noise of the plasma source. This research also includes the experimental validation of two new and distinct collimating RPA design types. Specifically, these design improvements include a 406 micron diameter single channel bore and a multi-channel plate (MCP) consisting of sixty-four 2 micron diameter bores, respectively. Both of these collimators relax the Debye length constraints within the electrode series and increase the instrument's range while minimizing the presence of space charge limitations. The single channel needle also has the added advantage of providing a relatively small cross-section to the incident plasma, thus minimizing pressure gradients and shock effects inherent to bulkier instrumentation. Experimental results obtained in the plume of the MiLiPulT are benchmarked against those of a traditional gridded RPA (having a 650 micron grid wire gap) and are reduced using an iterative fuzzy logic algorithm. Modifications to the classical RPA current collection theory include a thorough treatment of geometrical flux limitations due to an electrically floating cylindrical channel of high diameter to length aspect ratio. The differences between true and effective RPA collimating channel transparencies in the presence of a Maxwellian plasma are also addressed.

This Master's Thesis handles prestudy work and early hardware development that resulted in architectural definitions and prototype hardware of electronic ground support equipment. This equipment is destined to emulate the electric power consumption of the PPS5000 Hall Effect Thruster (HET), for use in satellite end-to-end tests of the all-electric Geostationary Satellite Electra, developed at OHB Sweden AB. The Thruster Emulator (TEM) was defined through a resulting compilation of intricate interdependent components that interface the satellite power system and the thruster, which yielded an architecture development to support some basic predefined emulator requirements. This architecture was then analyzed to form a base-line conceptual function of the emulator system, which incorporates the entire HET functionality. Six primary HET impedances were defined, of which the three most complex impedances were investigated fully. For the primary thruster discharge, research is shown of the complexity of implementing advanced electronic load hardware directly to the satellite's 5kW power system with respect to the transient primary plasma discharge during thruster start up, and with limitations on the electronic load reducing emulator-thruster similarities. Additionally, a fully functional plasma ignition emulator prototype circuit board was built to be used in the final hardware of the TEM to emulate the external HET cathode start-up functionality. Finally, a feasibility study for designing a possible solution for the large PPS5000 electromagnet impedance was performed, resulting in the manufacture of two prototype inductors with unsatisfying performance results according to the design requirements.

O presente trabalho aborda análises de sistemas de propulsão e manobra para comboios fluviais, e seus efeitos na manobrabilidade dos comboios. Analisam-se o sistema de propulsão convencional (propulsor mais leme), o sistema azimutal e o equipamento de proa auxiliar combinado com cada um destes sistemas de propulsão. Apresenta-se a modelagem matemática dos sistemas de propulsão e manobra citados, os quais serviram de base para implementação de um simulador computacional utilizado para obtenção dos resultados desta dissertação. As forças e momentos hidrodinâmicos são obtidos através do método das derivadas hidrodinâmicas para as simulações próximas à velocidade de serviço do comboio, enquanto para simulações em baixa velocidade utilizou um método semi-empírico baseado no princípio de cross-flow. Inicialmente, efetuou-se a validação do simulador com resultados da literatura para o caso do comboio com propulsão convencional. Em seguida, o modelo foi adaptado para os demais tipos de sistemas de propulsão e manobra propostos. Os resultados obtidos mostram que há uma maior eficiência do sistema de propulsão azimutal e do equipamento na proa para manobras em baixas velocidades, o que se torna adequado sua aplicação em comboios fluvial, pois essas embarcações navegam em velocidades menores se comparadas a outros tipos de embarcações. / The present work deal with analysis of propulsion and maneuvering systems for pusher-barge system, and results on the maneuverability of convoys. It analyzes the conventional propulsion system (rudder plus propeller), the azimuth system and combined auxiliary equipment bow with each of these propulsion systems. Presents the mathematical modeling of propulsion and maneuvering systems mentioned, which served as the basis for implementation of a computational simulator used to obtain the results of this dissertation. The hydrodynamic forces and moments are obtained by the method of hydrodynamic derivatives for simulations about service speed, while for simulations at low speed used a semi - empirical method based on the principle of cross-flow. Initially, performed the validation of the simulation results with the literature for the case of pusher-barge system with conventional propulsion. Then the model was adapted to other types of propulsion and maneuvering systems proposed. The results show that there is a greater efficiency of azimuth propulsion system and equipment in the bow to maneuver at low speeds, which makes it suitable for application in river transport, because these vessels navigate slower speeds compared to other types of vessels.

The current technological age is embodied by a constant push for increased performance and efficiency of electronic devices. This push is particularly observable for technologies that comprise free electron sources, which are used in various technologies including electronic displays, x-ray sources, telecommunication equipment, and spacecraft propulsion. Performance of these systems can be increased by reducing weight and power consumption, but is often limited by a bulky electron source with a high energy demand. Carbon nanotubes (CNTs) show favorable properties for field electron emission (FE) and performance as electron sources. This dissertation details the developments of a uniquely designed Spindt type CNT field emission array (CFEA), from initial concept to working prototype, to specifically prevent electrical shorting of the gate. The CFEA is patent pending in the United States. Process development enabled fabrication of a CFEA with a yield of up to 82%. Furthermore, a novel oxygen plasma etch process was developed to reverse shorting after CNT synthesis. CFEA testing demonstrates FE with a current density of up to 293 μA/cm² at the anode and 1.68 mA/cm² at the gate, with lifetimes in excess of 100 hours. A detailed analysis of eighty tested CFEAs revealed three distinct types of damage. Surprisingly, about half of the damaged chips are not electrically shorted, indicating that the CFEAs are very robust. Potential applications of this technology as cathodes for spacecraft electric propulsion were explored. Exposure to an operating electric propulsion thruster showed no significant effect or damage to the CFEAs, marking the first experimental study of CNT field emitters in an electric propulsion environment. A second effort in spacecraft propulsion is a collaboration with the Air Force Institute of Technology (AFIT). CFEAs are the payload on an AFIT developed Cube Satellite, called ALICE, to test electron emission in the space environment. ALICE has passed flight tests and is awaiting launch scheduled for 5 December 2013.

O presente trabalho aborda análises de sistemas de propulsão e manobra para comboios fluviais, e seus efeitos na manobrabilidade dos comboios. Analisam-se o sistema de propulsão convencional (propulsor mais leme), o sistema azimutal e o equipamento de proa auxiliar combinado com cada um destes sistemas de propulsão. Apresenta-se a modelagem matemática dos sistemas de propulsão e manobra citados, os quais serviram de base para implementação de um simulador computacional utilizado para obtenção dos resultados desta dissertação. As forças e momentos hidrodinâmicos são obtidos através do método das derivadas hidrodinâmicas para as simulações próximas à velocidade de serviço do comboio, enquanto para simulações em baixa velocidade utilizou um método semi-empírico baseado no princípio de cross-flow. Inicialmente, efetuou-se a validação do simulador com resultados da literatura para o caso do comboio com propulsão convencional. Em seguida, o modelo foi adaptado para os demais tipos de sistemas de propulsão e manobra propostos. Os resultados obtidos mostram que há uma maior eficiência do sistema de propulsão azimutal e do equipamento na proa para manobras em baixas velocidades, o que se torna adequado sua aplicação em comboios fluvial, pois essas embarcações navegam em velocidades menores se comparadas a outros tipos de embarcações. / The present work deal with analysis of propulsion and maneuvering systems for pusher-barge system, and results on the maneuverability of convoys. It analyzes the conventional propulsion system (rudder plus propeller), the azimuth system and combined auxiliary equipment bow with each of these propulsion systems. Presents the mathematical modeling of propulsion and maneuvering systems mentioned, which served as the basis for implementation of a computational simulator used to obtain the results of this dissertation. The hydrodynamic forces and moments are obtained by the method of hydrodynamic derivatives for simulations about service speed, while for simulations at low speed used a semi - empirical method based on the principle of cross-flow. Initially, performed the validation of the simulation results with the literature for the case of pusher-barge system with conventional propulsion. Then the model was adapted to other types of propulsion and maneuvering systems proposed. The results show that there is a greater efficiency of azimuth propulsion system and equipment in the bow to maneuver at low speeds, which makes it suitable for application in river transport, because these vessels navigate slower speeds compared to other types of vessels.

The I2T5, an iodine-propelled, cold gas thruster, developed by ThrustMe, France, is the first of its kind to make it successfully to space. Due to its simple, reliable and cost-effective design, it is a suitable propulsion system for CubeSat missions with low delta-V (ΔV) requirements. To ensure that the I2T5 performs at its peak, it is crucial to maintain good thermal control of the thruster, to keep it within the operational temperature range. The first flight measurements of the I2T5 provided insight into its thermal performance. It was observed that the required temperature to sublimate the iodine propellant was not reached within the expected time frame, which led to a longer warm-up period, and a reduction in thrust. The problem arose due to an unforeseen conductive thermal contact between the tank and the thruster walls. This thesis delves deeper into this issue, and focuses on alleviating the total conductive heat loss from the tank to the satellite frame, where the I2T5 is integrated. The insulating washer-bolt configuration of the I2T5 side panels is observed to be responsible for the conductive heat transfer. A preliminary analysis is performed to obtain an initial maximum for the conductive heat flux lost to the satellite frame. A plan of action is then determined to optimise the geometry, material or configuration of the insulating washers to lower the maximum heat flux value. Following this, an experiment was conducted with a new washer-bolt configuration to determine the heat flux values. A case study is performed for the orbital environment heat fluxes that the I2T5 would receive if it were integrated to a CubeSat in sun-synchronous orbit. An overview of results shows that, for the thermal simulations, all the methods employed to reduce the conductive heat loss at the frame were effective. The experiment provided neutral results, and would need to be repeated with different experimental parameters to have a clear perspective of the heat losses. In reality, the satellite frame receives radiative fluxes in addition to conductive heat fluxes, but radiation is not considered for this thesis, and is suggested as a prospective study.

Es wird gezeigt, dass die angestrebte Steuerung der Lastverteilung auf Pilotmeißel und Erweiterungswerkzeug durch den Einsatz eines hydraulischen Thrusters im Pilotstrang erreicht werden kann. Das zur Steuerung bestehende operative Fenster einer solchen Bohrgarnitur ist jedoch im Allgemeinen klein und bedarf für jeden Einsatzfall einer detaillierten Vorausplanung. Ein entsprechender Berechnungsansatz zur Simulation der Vorgänge in einer komplexen Bohrgarnitur mit schaltbarem Erweiterungswerkzeug wurde entwickelt und getestet. Er stützt sich auf die Bingham-Gleichung für die Bohrgeschwindigkeit, die für die speziellen Belange der vorliegenden Untersuchung modifiziert wurde. Die Einflüsse individueller operativer und konstruktiver Parameter auf das Steuerverhalten der komplexen Bohrgarnitur wurden eingehend untersucht. Die Auswertung der Ergebnisse führte zu allgemeinen Planungs- und Einsatzempfehlungen.

Alors que les applications spatiales prennent une place de plus en plus cruciale dans nos vies, les coûts d'opération des satellites doivent être réduits. Ceci peut être obtenu par l'utilisation de systèmes de propulsion électriques, plus efficients que leurs homologues chimiques traditionnellement utilisés. Une des technologies de propulsion électrique la plus performante et la plus utilisée est le propulseur à effet Hall, toutefois ce système reste complexe et peu compris. En effet de nombreuses questions, concernant le transport anormal des électrons ou les interactions plasma/paroi, sont encore ouvertes.Les réponses à ces questions sont basées sur des mécanismes cinétiques et donc ne peuvent être résolues par des modèles fluides. De plus les caractéristiques géométriques et temporelles de ces mécanismes les rendent difficilement observables expérimentalement. Par conséquent nous avons, pour répondre à ces questions, développé un code cinétique bi-dimensionnel.Grâce à un modèle simplifié de propulseur à effet Hall, nous avons observé l'importance de l'instabilité de dérive électronique pour le transport anormal. Ensuite en utilisant un modèle réaliste de propulseur, nous avons pu étudier les effets des interactions plasma/paroi sur la décharge plasma. Nous avons également pu quantifier les effets intriqués des émissions électroniques secondaires et de l'instabilité de dérive sur le transport anormal. Par une étude paramétrique sur les émissions électroniques secondaires, nous avons pu identifier trois régimes de décharge plasma. Finalement l'impact des ergols alternatifs a pu être étudié en utilisant des processus collisionnels réalistes. / As space applications are increasingly crucial in our daily life, satellite operating costs need to be decreased. This can be achieved through the use of cost efficient electric propulsion systems. One of the most successful and competitive electric propulsion system is the Hall effect thruster, but this system is characterized by its complexity and remains poorly understood. Indeed some key questions, concerning electron anomalous transport or plasma/wall interactions, are still to be answered.Answers to both questions are based on kinetic mechanisms, and thus cannot be solved with fluid models. Furthermore the temporal and geometrical scales of these mechanisms make them difficult to be experimentally measured. Consequently we chose, in order to answer those questions, to develop a bi-dimensional fully kinetic simulation tool.Using a simplified simulation of the Hall effect thruster, we observed the importance of the azimuthal electron drift instability for anomalous cross-field electron transport. Then, using a realistic model of a Hall effect thruster, we were able to study the effects of plasma/wall interactions on the plasma discharge characteristics, as well as to quantify the coupled effects of secondary electron emission and electron drift instability on the anomalous transport. Through parametric study of secondary electron emission, three plasma discharge regimes were identified. Finally the impact of alternative propellants was studied.

A computational model of the micro-ion thruster MiXI has been developed, analyzed, and partially verified. This model includes submodels that govern the physical, magnetic, electrostatic, plasma physics, and power deposition of the thruster. Over the past few years, theses have been conducted with the goal of running tests and analyzing the results; this model is used to understand how the thruster components interact so as to make predictions about, and allow for optimization of, the thruster operation. Testing is then performed on the thruster and the results are compared to the output of the code. The magnetic structure of the thruster was analyzed and numerous different configurations generated which were also evaluated by the optimizer and tested. Using the different configurations, models, and optimization tools, the total efficiency of the thruster is theoretically able to reach 69.4%. Operational testing of the thruster at many different throttle settings demonstrated a maximum total efficiency of 45.9 ±24.6%, discharge loss values as low as 109 ±25 eV/ion, and total power required as low as 50.5 ±0.1W to maintain thruster operation with beam extraction. Measurements of the plasma were taken using a Langmuir probe and the interpretation of the tests are used to verify the plasma physics submodel. Power draw measurements and analysis of the throttle inputs during testing are compared to the performance model outputs but were not accurate or consistent enough to fully verify the power deposition and plasma physics models. Analysis of the models and operational testing in this study have led to an increased understanding of the performance and operation of the MiXI-CP-V3 thruster, furthering the effort to create an efficient, flight capable micro-ion thruster.

This thesis explores the potential of utilizing metal-based plasma sources as a sustainable solution for high-powered electric propulsion and its implications for future interplanetary travel. Focusing on the Vacuum Arc Thruster and the Variable Specific Impulse Magnetoplasma Rocket engine, the study encompasses numerical simulations, analytical comparisons, and performance analyses to assess the feasibility of metal plasma fuels in space missions.The numerical analysis employs COMSOL Multiphysics to delve into the magnetohydrodynamics behavior within the VAT. Such simulation setup could provide valuable insights. Although the numerical results are disappointing for this paper, there exist possibilities within future work. The main hurdle is the simulation of vacuum. There are workarounds in COMSOL's Vacuum System Modeling tool which was not available for this thesis. Also, the used material properties were not suited for this high temperature plasma environment. The lack of material properties is a consequence of the insufficient research in the metal plasma field.Performance analysis is conducted on both the VAT and VASIMR engine, exploring efficiency, thrust capabilities, and feasibility for interplanetary missions. The results demonstrate the potential of metal-based plasma sources to reduce dependence on Earth for refueling and decrease mission costs. It is found that aluminum and magnesium have similar performance as the argon gas used in the VASIMR.Although challenges exist, such as integration problems and availability of material properties for metals in plasma states, the study underscores the promise of metal plasma fuels for sustainable space exploration. By advancing high-powered electric propulsion technologies, we move closer to realizing humanity's ambitious journey to distant celestial bodies. This research paves the way for future innovations, enabling a more self-sustaining space economy and unlocking new horizons of interplanetary travel.