High Efficiency Multistage Plasma Thrusters (HEMPTs) are a relatively new form of electric propulsion that show promise for use on a variety of missions and have several advantages over their older EP competitors. One such advantage is their long predicted lifetime and minimal wall erosion due to a unique periodic permanent magnet system. A laboratory HEMPT was built and donated by JPL for testing at Cal Poly. Previous work was done to characterize the performance of this thruster and it was found to exhibit a large plume divergence, resulting in decreased thrust and specific impulse. This thesis explores the design and application of a magnetic shield to modify the thruster’s magnetic field to force more ion current towards the centerline. A previous Cal Poly thesis explored the same concept, and that work is continued and furthered here. The previous thesis tested a shield which increased centerline current but decreased performance. A new shield design which should avoid this performance decrease is studied here. Magnetic modelling of the thruster was performed using COMSOL. This model was verified using guassmeters to measure the field strength at many discrete points within and near the HEMPT, with a focus on the ionization channel and exit plane. A shield design which should significantly reduce the radial field strength at the exit plane without affecting the ionization channel field was modelled and implemented. The HEMPT was tested in a vacuum chamber with and without the shield to characterize any change to performance characteristics. Data were collected using a nude Faraday probe and retarding potential analyzer. The data show a significant increase in centerline current with the application of the shield, but due to RPA malfunction and thruster failure the actual change in performance could not be concluded. The unshielded HEMPT was characterized, however, and was found to produce 12.1 +/- 1.3 mN of thrust with a specific impulse of 1361 +/- 147s. The thruster operated with a total efficiency of 10.63 +/- 3.66%, an efficiency much lower than expected. A large contributor to this low efficiency is likely the use of argon in place of xenon. Its lower mass and higher ionization energy make it a less efficient propellant choice. Further, the thruster is prone to overheating, indicating that significant thermal losses are present in this design.

Powering spacecraft with electric propulsion is becoming more common, especially in CubeSat-class satellites. On account of the risk of spacecraft interactions, it is important to have robust analysis and modeling tools of electric propulsion engines, particularly of the plasma plume. The Navier-Stokes equations used in classic continuum computational fluid dynamics do not apply to the rarefied plasma, and therefore another method must be used to model the flow. A good solution is to use the DSMC method, which uses a combination of particle modeling and statistical methods for modeling the simulated molecules. A DSMC simulation known as SINATRA has been developed with the goal to model electric propulsion plumes. SINATRA uses an octree mesh, is written in C++, and is designed to be expanded by further research. SINATRA has been initially validated through several tests and comparisons to theoretical data and other DSMC models. This thesis examines expanding the functionality of SINATRA to simulate charged particles and make SINATRA a DSMC-PIC hybrid. The electric potential is calculated through a 7-point 3D stencil on the mesh nodes and solved with a Gauss-Seidel solver. It is validated through test cases of charged particles to demonstrate the accuracy and capabilities of the model. An ambipolar diffusion test case is compared to a neutral diffusion case and the electric field is shown to stabilize the diffusion rate. A steady state flow test case shows the simulation is able to stabilize and solve the electric potential for a plume-like scenario. It includes additional features to simplify further research including a comprehensive user manual, industry-standard version control, text file inputs, GUI control, and simple parallelism of the simulation. Compilation and execution are standardized to be simple and platform independent to allow longevity of the code base. Finally, the execution bottlenecks of linking particles to cells and particle moving were removed to reduce the simulation time by 95%.

Since 2000, a relatively new electric thruster concept has been in research, development, and production at Thales Electron Devices in Germany. This High Efficiency Multistage Plasma Thruster, or HEMPT, has promising lifetime capabilities due to its plasma confinement system. However, the permanent magnet system that offers this and other benefits also creates a hollow plume, where ions are accelerated at angles rather than up the thruster centerline, causing a dip in ion current along the centerline. A laboratory model, built at JPL, was run at Cal Poly to characterize this plume shape and implement a shield to restore a conical shape to the plume. A similar solution was used on a different type of thruster, a cylindrical hall thruster, at Princeton with excellent results. A shield was designed to shunt the magnetic field outside the thruster, where the Princeton experiments have identified a radial magnetic field as the cause for this hollow plume. The thruster was run with and without the shield, taking measurements of the ion current in the plume using a linear probe drive. The shield fixed the plume shape, increasing centerline current by 48%, however it also had detrimental effects on thruster performance, causing a decrease in thrust, specific impulse, and cut the total efficiency in half. The shield design was reexamined and a new design has been suggested for future testing of the HEMPT to restore performance while still fixing the plume shape.

Les hydrazines utilisées en propulsion sont aujourd’hui identifiées par la réglementation REACH comme des substances extrêmement préoccupantes (SVHC) et leur utilisation est par conséquent menacée. Les HEDM (High Energy Density Material) représentent une classe de composés à l’architecture polyazotée voire strictement azotée dont les performances énergétiques théoriques sont en rupture avec les technologies actuelles et dont la décomposition en N2 offrirait une réponse à cette règlementation. De plus, leur utilisation simplifierait la technologie des lanceurs et permettrait d’abaisser leur coût. Deux candidats potentiels ont donc été proposés par les tutelles du laboratoire en raison de leurs excellentes performances théoriques : la triaziridine (N3H3) et la tétrazétidine (N4H4). L’objectif général de cette thèse est de développer de nouvelles méthodologies de synthèse de composés polyazotés et d’étudier leur réactivité afin de valider l’accès aux structures originales telles que les cycles triaziridine et tétrazétidine. Une toute nouvelle méthodologie d’homologation par ajout d’azodicarboxylates permettant d’accéder à des systèmes polyazotés linéaires supérieurs (N3, N4, N5, N6…) a été mise au point. Des preuves structurales de ces enchainements azotés inédits ont été obtenues par DRX. La réactivité par activation régiosélective et par oxydation des systèmes synthétisés a ensuite été étudiée afin d’accéder aux structures polyazotées cycliques / Hydrazines for propulsion have been identified by REACH regulation as Substances of Very High Concern (SVHC) and their use is therefore threatened. High Energy Density Materials (HEDM) represent a class of polynitrogen compounds with computed energetic performances breaking away from existing technologies. Besides solving toxicity issues thanks to their decomposition in molecular nitrogen, their use would highly simplify launcher’s technologies and decreases their cost. Two candidates have been proposed by the CNES and ArianeGroup to replace hydrazines: triaziridine (N3H3) and tetrazetidine (N4H4). The main goal of this thesis is to develop new methodologies for the synthesis of polynitrogen compounds and to investigate their reactivity to access to original structures such as triaziridine and tetrazetidine. Homologation of simple nitrogen-based compounds with azodicarboxylates enabled us to access new original superior polynitrogen molecules (N3, N4, N5, N6…). Structural evidences of these new polynitrogen backbones have been obtained by X-ray diffraction. Their reactivity by regioselective activation and by oxidation has been studied to access cyclic polynitrogen structures

<p>A series of experimental tests were performed to study the transient response of gas/liquid injectors exposed to transverse detonation waves. A total of four acrylic injectors were tested to compare the response between gas/liquid and liquid only injectors, as well as compare the role of various geometric features of the notional injector design. Detonation waves are produced through the combustion of ethylene and oxygen, at conditions to produce average wave pressures between 128 and 199 psi. The injectors utilize water and nitrogen to simulate the injection of liquid and gaseous propellants respectively. Quantification of injector refill times was possible through the use of a high-speed camera recording at a frame rate of 460,000 frames per second. High frequency pressure measurements in both the gaseous and liquid manifolds allow for quantification of the temporal pressure response of the injectors. Variations in simulant mass flow rates, measured through the use of sonic nozzles and cavitating venturis, produce pressure drops up to 262 psi across the injector. Injector refill times are found to be a strong function of the impulse delivered across the injector. Manifold acoustics were found to play a large role in injector response as manifolds that promote manifold over-pressurizations during the injector recovery period recover quicker than designs that limit this response.</p>

Hybrid rocket motors have become of great international interest during the last couple of years. A hybrid rocket motor is propelled by the use of a solid fuel and a liquid oxidizer. The fundamental principle of the hybrid propelled system is that the liquid oxidizer is injected into a combustion chamber to enable the combustion of the solid fuel. The exhaust gases are then accelerated through a nozzle to supersonic velocity to produce the desired level of thrust. To describe the overall performance of a propulsion system, it is common use the specifc impulse which expresses the performance as the total impulse per mass unit of propellant. However, in order to optimize a propulsion system, it is necessary to consider the entire system with the oxidizer tank, feed system, combustion chamber and nozzle. The issue with using the specifc impulse as a performance index is that it does not consider the total mass of the propulsion system. Therefore, this thesis will instead analyze the system specifc impulse, which expresses the performance as the total impulse per mass unit of propulsion system. By studying the entire hybrid propulsion system it is possible to determine the relations between the various parameters of the diferent components and should therefore be able to optimize the mass, volume and system specifc impulse of the system. This master’s thesis aims to illustrate how the hybrid propulsion system can be optimized depending on various fxed parameters. This analysis studies a generic hybrid propulsion systemwith Hydroxyl-terminated polybutadiene (HTPB) as a solid fuel with diferent combinations ofoxidizers. Each oxidizer- and fuel confguration shall have identical combustion chamber presssures and shall generate the same total impulse. Nevertheless, each combination will result indiferent specifc impulses since the optimal confguration for each combination will generate diffferent oxidizer and fuel masses. It is then desirable to analyze how the diferent components ofthe propulsion system are affected by the required oxidizer and fuel for each optimal confgurationand how it drives the design of the system and generates diferent system specifc impulses.

La thèse porte sur l’étude de l’influence des textures sur le mouillage et la propulsion. Trois situations ont été considérées, selon la taille des textures utilisées.Des textures nanométriques hydrophobes permettent d’obtenir des surfaces aérophiles. Lorsque ces surfaces sont immergées dans un bain, elles restent recouvertes d’un fin film d’air et ouvrent toute une classe de nouveaux problèmes de mouillage, où les interfaces gaz – liquide sont inversées par rapport aux situations traditionnelles. Nous avons décrit l’étalement d’une bulle d’air sur une surface aérophile, la dépression capillaire ou encore la dynamique de bulles sur des fils.En situation de lévitation, des textures de l’ordre du millimètre permettent de rediriger efficacement le flux d’air qui sépare un objet de son support. L’écoulement étant contrôlé, une direction privilégiée peut être choisie et l’objet se trouve alors efficacement propulsé. Selon l’emplacement des textures, un entrainement visqueux ou une propulsion par effet fusée peuvent être observés.Sur des créneaux millimétriques recouverts de nanotextures hydrophobes, l’eau est en situation non-mouillante. Il suffit d’une toute petite inclinaison de la surface pour qu’une goutte dévale, et elle atteint rapidement des vitesses importantes puisque la friction est très faible. La présence des macrotextures sur la surface permet de ralentir considérablement la goutte : l’étude a porté sur l’optimisation du contrôle d’une goutte, éventuellement visqueuse. / This thesis deals with the influence of textures on wetting and propulsion. Three situations have been considered, depending on the texture size.Aerophilic surfaces can be obtained with hydrophobic nanometric structures. When immerged in a liquid bath, these surfaces remain covered by a thin plastron of air. This oppens a new class of problems where gas – liquid interfaces are exchanged, compared to usual studies. We described the spreading of an air bulle over an aerophilic surface, capillary depression and the dynamics of a bubble on a wire.Millimetric sutructures allow an efficient redirection of the air cushion between a levitating object and its substrate. Because the flux is controlled, a specific direction can appear, and the object is efficiently propelled. Depending on the textures location, viscous entrainement or rocket effect can be the propulsive mechanism.Hydrophobic nanotextures are used to generate non-wetting situation of water. A tiny angle of tilt of the surface is enough to see a drop mouving; its velocity is high because of the low friction. Macrotextures, as millimetric crennels slow down very efficiently the drop: the study optimized the control of the drop (possibly viscous) motion.

Thesis: S.B., Massachusetts Institute of Technology, Department of Electrical Engineering, 1965 / "September 1965." / Includes bibliographical references (leaf 65). / by Eduardo Jose Barragan Schenone. / S.B. / S.B. Massachusetts Institute of Technology, Department of Electrical Engineering

Electric propulsion systems utilize electrical energy to produce thrust for spacecraft propulsion. These systems have multiple applications ranging from Earth orbit North-South station keeping to solar system exploratory missions such as NASA’s Discovery, New Frontiers, and Flagship class missions that focus on exploring scientifically interesting targets. In an electromagnetic thruster, a magnetic field interacting with current in an ionized gas (plasma) accelerates the propellant to produce thrust. Pulsed inductive thrusters rely on an electrodeless discharge where both the magnetic field in the plasma and the plasma current are induced by a time-varying current in an external circuit. The multi-dimensional acceleration model for a pulsed inductive plasma thruster consists of a set of circuit equations describing the electrical behavior of the thruster coupled to a one-dimensional momentum equation that allow for estimating thruster performance. Current models lack a method to account for the time-varying energy distribution in an inductive plasma accelerator.

Combustion emissions from aviation operations contribute significantly to climate change and air pollution. Accordingly, there is increasing interest in advancing battery-powered propulsion for aviation applications to reduce emissions. As batteries continue to improve, it is essential to recognize breakthroughs in battery specific energy in the context of air transport vehicles. Most electric aircraft designs and programs have focused on small aircraft because of restrictive battery performance. This work presents a feasibility assessment for an all-electric airliner based on an Airbus A220-100 with turbofan engines replaced by electric motors and propellers. The analysis compares the performance characteristics of the electric airliner to the A220-100 and establishes several configurations with varying battery pack-specific energy. The short-term electric airliner could replace conventional aircraft on very short, high-density missions. In contrast, the long-term electric airliner requires significant battery technology improvements that are not currently foreseen. The alternative long-term electric airliner could complete half of the A220-100’s missions, but the necessary specific energy value is also not anticipated shortly. All-electric airliners would significantly impact manufacturing, operations, costs, and emissions but are commercially infeasible with current battery technology. Additional development of more advanced battery technology is required to increase the specific energy of battery packs, enhance battery safety and reliability, and develop lighter high-power electric motors.