Artykuły w czasopismach: „Gridded thruster”

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Yamashita, Yusuke, Ryudo Tsukizaki, Yuta Yamamoto, Daiki Koda, Kazutaka Nishiyama i Hitoshi Kuninaka. "Azimuthal ion drift of a gridded ion thruster". Plasma Sources Science and Technology 27, nr 10 (16.10.2018): 105006. http://dx.doi.org/10.1088/1361-6595/aae29b.

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Grondein, P., T. Lafleur, P. Chabert i A. Aanesland. "Global model of an iodine gridded plasma thruster". Physics of Plasmas 23, nr 3 (marzec 2016): 033514. http://dx.doi.org/10.1063/1.4944882.

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Soulas, George C. "Modeling Neutral Densities Downstream of a Gridded Ion Thruster". Journal of Propulsion and Power 27, nr 3 (maj 2011): 538–52. http://dx.doi.org/10.2514/1.b34094.

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Dobkevicius, Mantas, i Davar Feili. "Multiphysics Model for Radio-Frequency Gridded Ion Thruster Performance". Journal of Propulsion and Power 33, nr 4 (lipiec 2017): 939–53. http://dx.doi.org/10.2514/1.b36182.

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Williams, Logan T., i Mitchell L. R. Walker. "Ion production cost of a gridded helicon ion thruster". Plasma Sources Science and Technology 22, nr 5 (27.09.2013): 055019. http://dx.doi.org/10.1088/0963-0252/22/5/055019.

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Aanesland, Ane, Dmytro Rafalskyi, Jerome Bredin, Pascaline Grondein, Noureddine Oudini, Pascal Chabert, Dimitry Levko, Laurent Garrigues i Gerardus Hagelaar. "The PEGASES Gridded Ion-Ion Thruster Performance and Predictions". IEEE Transactions on Plasma Science 43, nr 1 (styczeń 2015): 321–26. http://dx.doi.org/10.1109/tps.2014.2369534.

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Magaldi, Bernardo, Júlia Karnopp, Argemiro da Silva Sobrinho i Rodrigo Pessoa. "A Global Model Study of Plasma Chemistry and Propulsion Parameters of a Gridded Ion Thruster Using Argon as Propellant". Plasma 5, nr 3 (28.07.2022): 324–40. http://dx.doi.org/10.3390/plasma5030025.

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This work reports on the (zero-dimensional) global model study of argon plasma chemistry for a cylindrical thruster based on inductively coupled plasma (ICP) whose output has a system of two grids polarized with each other with direct current potential. The global model developed is based on particle and energy balance equations, where the latter considers both charged and neutral species. Thus, the model allows the determination of the neutral gas temperature. Finally, this study also investigated the role of excited species in plasma chemistry especially in the ions production and its implications for propulsion parameters, such as thrust. For this, the study was carried out in two different scenarios: (1) one taking into account the metastable species Arr and Arp (multi-step ionization), and (2) the other without these species (single-step ionization). Results indicates a distinct behavior of electron temperature with radiofrequency (RF) power for the investigated cases. On the other hand, the gas temperature is almost the same for investigated power range of up to 900 W. Concern propulsion analysis, a thrust of 40 mN at 450 W was verified for case (1), which represents a remarkable thrust value for electric thrusters.

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Neumann, Andreas, i Nina Sarah Mühlich. "Ground-Based Experiment for Electric Propulsion Thruster Plume—Magnetic Field Interaction". Aerospace 10, nr 2 (26.01.2023): 117. http://dx.doi.org/10.3390/aerospace10020117.

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Electric space propulsion is a technology which is employed on a continuously increasing number of spacecrafts. While the current focus of their application area is on telecommunication satellites and on space exploration missions, several new ideas are now discussed that go even further and apply the thruster plume particle flow for transferring momentum to targets such as space debris objects or even asteroids. In these potential scenarios, the thruster beam impacts on distant objects and subsequently generates changes in their flight path. One aspect which so far has not been systematically investigated is the interaction of the charged particles in the propulsion beam with magnetic fields which are present in space. This interaction may result in a deflection of the particle flow and consequently affect the aiming strategy. In the present article, basic considerations related to the interaction between electric propulsion thruster plumes and magnetic fields are presented. Experiments with respect to these questions were conducted in the high-vacuum plume test facility for electric thrusters (STG-ET) of the German Aerospace Center in Göttingen utilizing a gridded ion thruster, an RIT10/37, and a Helmholtz coil to generate magnetic fields of varying field strength. It was possible to detect a beam deflection on the RIT ion beam caused by a magnetic field with an Earth-like magnetic field strength.

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Williams, Logan T., i Mitchell L. R. Walker. "Initial Performance Evaluation of a Gridded Radio Frequency Ion Thruster". Journal of Propulsion and Power 30, nr 3 (maj 2014): 645–55. http://dx.doi.org/10.2514/1.b35018.

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Rovey, Joshua L., i Alec D. Gallimore. "Dormant Cathode Erosion in a Multiple-Cathode Gridded Ion Thruster". Journal of Propulsion and Power 24, nr 6 (listopad 2008): 1361–68. http://dx.doi.org/10.2514/1.37031.

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Quarta, Alessandro A. "Preliminary Trajectory Analysis of CubeSats with Electric Thrusters in Nodal Flyby Missions for Asteroid Exploration". Remote Sensing 17, nr 3 (1.02.2025): 513. https://doi.org/10.3390/rs17030513.

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This paper studies the performance of an interplanetary CubeSat equipped with a continuous-thrust primary propulsion system in a heliocentric mission scenario, which models a nodal flyby with a potential near-Earth asteroid. In particular, the mathematical model discussed in this work considers a small array of (commercial) miniaturized electric thrusters installed onboard a typical CubeSat, whose power-generation system is based on the use of classic solar panels. The paper also discusses the impact of the size of thrusters’ array on the nominal performance of the transfer mission by analyzing the trajectory of the CubeSat from an optimization point of view. In this context, the propulsive characteristics of a commercial electric thruster which corresponds to a iodine-fueled gridded ion-propulsion system are considered in this study, while the proposed procedure can be easily extended to a generic continuous-thrust propulsion system whose variation in thrust magnitude and specific impulse as a function of the input electric power is a known analytic function. Using an indirect approach, the paper illustrates the optimal guidance law, which allows the interplanetary CubeSat to reach a given solar distance, with the minimum flight time, by starting from a circular (ecliptic) parking orbit of assigned radius. The mission scenario is purely two-dimensional and models a rapid nodal flyby with a near-Earth asteroid whose nodal distance coincides with the solar distance to be reached.

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Chabert, P., J. Arancibia Monreal, J. Bredin, L. Popelier i A. Aanesland. "Global model of a gridded-ion thruster powered by a radiofrequency inductive coil". Physics of Plasmas 19, nr 7 (lipiec 2012): 073512. http://dx.doi.org/10.1063/1.4737114.

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Yamashita, Yusuke, Ryudo Tsukizaki, Koda Daiki, Yoshitaka Tani, Ryo Shirakawa, Kana Hattori i Kazutaka Nishiyama. "Plasma hysteresis caused by high-voltage breakdown in gridded microwave discharge ion thruster μ10". Acta Astronautica 185 (sierpień 2021): 179–87. http://dx.doi.org/10.1016/j.actaastro.2021.05.001.

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Rovey, Joshua L., i Alec D. Gallimore. "Ion energy measurements near a dormant cathode in a multiple-cathode gridded ion thruster". Physics of Plasmas 14, nr 3 (marzec 2007): 033505. http://dx.doi.org/10.1063/1.2536514.

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Fu, Chencong, Yicheng Dong, Yifei Li, Weizong Wang, Zihan Wang i Wei Liu. "Kinetic simulations of low-pressure inductively coupled plasma: an implicit electromagnetic PIC/MCC model with the ADI-FDTD method". Journal of Physics D: Applied Physics 57, nr 13 (4.01.2024): 135201. http://dx.doi.org/10.1088/1361-6463/ad1729.

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Abstract Low-pressure inductively coupled plasma (ICP) is promising for space electric propulsion. For the first time, an implicit electromagnetic particle-in-cell Monte Carlo collision model based on the alternating-direction-implicit finite-difference time-domain (ADI-FDTD) method is developed to investigate low-pressure xenon plasma characteristics of a miniature ICP source. The induced simulated electric field is well consistent with that calculated by the finite element method, indicating that this method can provide an accurate estimation of the electromagnetic field. The simulation time step used in the ADI-FDTD method is no longer restricted by the Courant–Friedrichs–Lewy constraints. Compared with the FDTD method, the ADI-FDTD method increases the size of the time step and significantly improves computational efficiency. The method is validated by comparing the simulated and measured electron density and plasma potential profile and reasonable agreement is reached. Therefore, the model is used to investigate the temporal and spatial distribution of plasma properties and the influence of the current amplitude of radio frequency (RF) coil, applied frequency of RF coil and neutral gas pressure on the plasma dynamics in the ionization chamber of a miniature gridded RF ion thruster. To explain the influence of the operating parameters, a concept called ‘the energy relaxation characteristics of electrons in response to the change of electric field’ is proposed and verified. The simulations also find that the oscillation frequency of plasma properties is twice the applied frequency of RF coil. The oscillation characteristics reveal the dynamic energy balance in the ICP. The experiment on the gridded RF ion thruster BHRIT-4 confirms the oscillation by measuring the plasma sheath potential.

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Yamashita, Yusuke, Ryudo Tsukizaki i Kazutaka Nishiyama. "Effect of ion beam extraction on neutral density distribution inside a gridded microwave discharge ion thruster". Vacuum 200 (czerwiec 2022): 110962. http://dx.doi.org/10.1016/j.vacuum.2022.110962.

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Tsukizaki, Ryudo, Yuta Yamamoto, Daiki Koda, Yamashita Yusuke, Kazutaka Nishiyama i Hitoshi Kuninaka. "Azimuthal velocity measurement in the ion beam of a gridded ion thruster using laser-induced fluorescence spectroscopy". Plasma Sources Science and Technology 27, nr 1 (17.01.2018): 015013. http://dx.doi.org/10.1088/1361-6595/aa9f9a.

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Kozakov, Ruslan, Maximilian Maigler, Jochen Schein i Neil Wallace. "Determination of Self-Neutralization Phenomena of Ion Beams with Langmuir Probe Measurements and PIC-DSMC Simulations". Applied Sciences 14, nr 8 (19.04.2024): 3470. http://dx.doi.org/10.3390/app14083470.

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Small mN-class gridded ion thrusters are usually tested in a vacuum chamber without the use of a neutralizer, relying on self-neutralization of the ion beam due to interaction with facility walls. Langmuir probe measurements performed immediately downstream of such a thruster reveal values of the plasma potential of several hundreds of volts. If this locally very high potential indeed exists, it would have significant impact on the erosion rate of RIT grids and thus reduce the lifetime of thrusters compared to the generally accepted plasma potential of a few tens of volts. Further measurements performed with a movable Langmuir and emissive probes indicate that the probe mount violates the ability of the ion beam to self-neutralize. This is concluded due to dependence of the measured potential value on the degree of neutralization introduced in the experiment. Particle-in-cell and direct-simulation Monte Carlo simulations of the ion beam corresponding to experimental conditions (ion energy EXe+=1.5 keV and ion beam current IXe+=17 mA) are carried out to determine the phenomena responsible for the self-neutralization; mainly, reactions with neutral species such as ionization by electron or ion impact and secondary electron emission (SEE) from the facility walls are compared. Reasonable agreement with measurements is achieved, and SEE is determined to be the primary source of electrons, indicating that facility and measurement disturbance effects majorly influence testing of (non-neutralized) ion beams. Further, limitations of the applicability of probe diagnostics on non-neutralized ion beams are described.

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Gomez, I., KL Aplin, A. Lawrie i CA Toomer. "Modelling an Ion Thruster for a Small Spacecraft in Very Low Earth Orbit". Journal of Physics: Conference Series 2702, nr 1 (1.02.2024): 012019. http://dx.doi.org/10.1088/1742-6596/2702/1/012019.

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Abstract A gridded ion thruster running on two different propellants (Xenon and Iodine) and sited within a 3U CubeSat satellite, is modelled in a Low-Earth-Orbit (altitude 400 km), using a Particle-in-Cell approach. Charged exchange collisions cause a plume backflow, which results in erosion or contamination of external spacecraft surfaces. In particular, this research is motivated by evaluating the risks to solar panel arrays from plume backflow. At low altitudes there is a wide range of ambient species able to interact electrostatically with the ion plume. In particular one must consider the plasma potential of the incoming particle flux at the solid boundaries as well as a sheath comparison and the temperature of the solar panel surfaces. This enables evaluation of the effect of temperature on the charged exchange region. A Particle-in-Cell is used, with a hybrid approach where electrons are treated as a fluid and the propellant as kinetic particles. Our results compare surface ablation for two propellants, focusing on solar panel arrays which are considered to be especially vulnerable to the backflow of ions from the plume expansion. It is found that the flux of incoming particles increases for lower satellite surface temperatures. Furthermore, Xenon results in having a lower overall effect on the sensitivity of the particle flux in comparison to Iodine.

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Alifano, Filippo, Mario Panelli i Francesco Battista. "Preliminary Design Tool for Medium-Low-Power Gridded Ion Thrusters". Applied Sciences 13, nr 9 (1.05.2023): 5600. http://dx.doi.org/10.3390/app13095600.

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Gridded ion thrusters (GITs) are an established technology that, by covering a wide range of power class, allows one to accomplish a lot of space mission types. Many analysis tools and analytical models describing the physics of GITs are present in the open literature, while there is a lack of tools for preliminary design, considering the mission requirements (i.e., thrust or power). Thus, in this work, a tool that takes as input thrust or power and that combines analytical formulas, describing GITs’ physics; a curve-fitting approach, exploiting data from different ion thrusters present in the open literature; and an FEMM (finite element method magnetics) simulation has been developed and validated against known medium-low-power (<5 kW) gridded ion thrusters (e.g., NSTAR, XIPS, ETS-8). Some of the main outputs of the developed tool are its specific impulse, efficiencies, voltages, and propellant flow rate. The results obtained by the tool have been in good agreement with the real performance and working parameters of the thrusters selected for the validation, obtaining an average error of less than 5–10%. The tool has been also compared with a tool proposed in the literature as a possible design tool, which makes use of a simple macroscopic plasma-source simulation (SMPS) code with a genetic algorithm (GA) and obtains slightly more accurate results on average. Finally, the tool has been exploited for the design of a very low-power GIT (100 W) that is able to produce 2 mN of thrust, as the interest of the scientific community in miniaturizing electric engines has recently grown because they could enable new space missions.

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Dale, Ethan, Benjamin Jorns i Alec Gallimore. "Future Directions for Electric Propulsion Research". Aerospace 7, nr 9 (20.08.2020): 120. http://dx.doi.org/10.3390/aerospace7090120.

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The research challenges for electric propulsion technologies are examined in the context of s-curve development cycles. It is shown that the need for research is driven both by the application as well as relative maturity of the technology. For flight qualified systems such as moderately-powered Hall thrusters and gridded ion thrusters, there are open questions related to testing fidelity and predictive modeling. For less developed technologies like large-scale electrospray arrays and pulsed inductive thrusters, the challenges include scalability and realizing theoretical performance. Strategies are discussed to address the challenges of both mature and developed technologies. With the aid of targeted numerical and experimental facility effects studies, the application of data-driven analyses, and the development of advanced power systems, many of these hurdles can be overcome in the near future.

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Gallimore, Alec D., Joshua L. Rovey i Daniel A. Herman. "Erosion Processes of the Discharge Cathode Assembly of Ring-Cusp Gridded Ion Thrusters". Journal of Propulsion and Power 23, nr 6 (listopad 2007): 1271–78. http://dx.doi.org/10.2514/1.27897.

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Borgue, O., F. Valjak, M. Panarotto i O. Isaksson. "SUPPORTING ADDITIVE MANUFACTURING TECHNOLOGY DEVELOPMENT THROUGH CONSTRAINT MODELLING IN EARLY CONCEPTUAL DESIGN: A SATELLITE PROPULSION CASE STUDY". Proceedings of the Design Society: DESIGN Conference 1 (maj 2020): 817–26. http://dx.doi.org/10.1017/dsd.2020.289.

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AbstractFunction and constraints modelling are implemented to design two gridded ion thrusters for additive manufacturing (AM). One concept takes advantage of AM design freedom, disregarding AM limitations and is not feasible. The other concept considers AM limitations and is manufacturable and feasible. Constraints modelling highlights AM capabilities that can be improved, showing where future investment is needed. Constraints representation can also support the creation of technology development roadmaps able to identify areas of AM technologies that must be improved.

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Wang, Xiaoxiang, i Ilya Tsvankin. "Ray-based gridded tomography for tilted transversely isotropic media". GEOPHYSICS 78, nr 1 (1.01.2013): C11—C23. http://dx.doi.org/10.1190/geo2012-0066.1.

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Reflection tomography in the migrated domain can help reconstruct heterogeneous, anisotropic velocity fields needed for accurate depth imaging of complex geologic structures. The presence of anisotropy, however, increases the uncertainty in velocity analysis and typically requires a priori constraints on the model parameters. Here, we develop a 2D P-wave tomographic algorithm for heterogeneous transversely isotropic media with a tilted symmetry axis (TTI) and investigate the conditions necessary for stable estimation of the symmetry-direction velocity [Formula: see text] and the anisotropy parameters [Formula: see text] and [Formula: see text]. The model is divided into rectangular cells, and the parameters [Formula: see text], [Formula: see text], [Formula: see text], and the tilt [Formula: see text] of the symmetry axis are defined at the grid points. To increase the stability of the inversion, the symmetry axis is set orthogonal to the imaged reflectors, with the tilt interpolated inside each layer. The iterative migration velocity analysis involves efficient linearized parameter updating designed to minimize the residual moveout in image gathers for all available reflection events. The moveout equation in the depth-migrated domain includes a nonhyperbolic term that describes long-offset data, which are particularly sensitive to [Formula: see text]. Synthetic tests for models with a “quasi-factorized” TTI syncline (i.e., [Formula: see text] and [Formula: see text] are constant inside the anisotropic layer) and a TTI thrust sheet demonstrate that stable parameter estimation requires either strong smoothness constraints or additional information from walkaway VSP (vertical seismic profiling) traveltimes. If the model is quasi-factorized with a linear spatial variation of [Formula: see text], it may be possible to obtain the interval TTI parameters just from long-spread reflection data.

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Liu, Qingguo, Xinxue Liu i Jian Wu. "A Fast Computational Method for the Minimum Duration Transfer Trajectories of Space-to-Ground Vehicles". Mathematical Problems in Engineering 2019 (20.05.2019): 1–17. http://dx.doi.org/10.1155/2019/5319530.

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On the conditions that the spacecraft engine is in finite thrust mode and the maneuver time is given, it takes a long time to compute the minimum duration transfer trajectories of space-to-ground vehicles, which is mainly because the initial values of the adjoint variables involved in the optimization model have no definite physical meanings and the model is sensitive to them. In order to develop space-to-ground transfer trajectory programmes in real time in an uncertain environment for the decision makers, we propose a fast method for computing the minimum duration transfer trajectories of space-to-ground vehicles with the given position of the landing point and the arbitrary maneuver point. First, the optimization model based on the hybrid method is established to compute the minimum duration transfer trajectory. Then, the region composed of maneuverable points is gridded and the initial values of the adjoint variables and the values of partial state variables of the minimum duration transfer trajectories at all gridded points are computed and saved to a database. Finally, the predicted values of the initial values of the adjoint variables and the values of partial state variables at any maneuver point within the region composed of maneuverable points are computed by using a binary cubic interpolation method. Finally, the minimum duration transfer trajectory is obtained by the hybrid method which takes the neighborhood of the predicted values as the search ranges of the initial values of the adjoint variables and the values of partial state variables. Simulation results demonstrate that the proposed method, which requires only 2.93% of the computational time of the hybrid method, can improve substantially the computational time of the minimum duration transfer trajectory of a space-to-ground vehicle under the guarantee of ensuring accuracy. The methodology of converting the time domain into the space domain is well applied in this paper.

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Banazadeh, A., F. Saghafi, M. Ghoreyshi i P. Pilidis. "Experimental and computational investigation into the use of co-flow fluidic thrust vectoring on a small gas turbine". Aeronautical Journal 112, nr 1127 (styczeń 2008): 17–25. http://dx.doi.org/10.1017/s0001924000001950.

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Abstract This paper presents the application of a relatively new technique of fluidic thrust-vectoring (FTV), named Co-flow, for a small gas-turbines. The performance is obtained via experiment and computational fluid dynamics (CFD). The effects of a few selected parameters including the engine throttle setting, the secondary air mass-flow rate and the secondary slot height upon thrust-vectoring performance are provided. Thrust vectoring performance is characterised by the ability of the system to deflect the engine thrust with respect to the delivered secondary air mass-flow rate. The experimental study was conducted under static conditions in an outdoor environment at Cranfield University workshop that was especially designed for this purpose. As part of this investigation, the system was modelled by CFD techniques, using Pointwise’s Gridgen software and the three-dimensional flow solver, Fluent. Also, Cranfield’s gas-turbine performance code (TurboMatch) was utilised to estimate boundary conditions for the CFD analysis with respect to the integrated nozzle. The presented technique is easy-to-use approach and offers better result for thrust-vectoring problems than previously published works. Experimental results do show the overall viability of the blowing slot mechanism as a means of vectoring the engine thrust, with the current configuration. Computational predictions are shown to be consistent with the experimental observations and make the CFD model a reliable tool for predicting Co-flow fluidic thrust-vectoring performance of similar systems.

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Chandler, Val W., i Kelley Carlson Malek. "Moving‐window Poisson analysis of gravity and magnetic data from the Penokean orogen, east‐central Minnesota". GEOPHYSICS 56, nr 1 (styczeń 1991): 123–32. http://dx.doi.org/10.1190/1.1442948.

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Analytical correlation of gravity and magnetic data through moving‐window application of Poisson's theorem is useful in studying the complex Precambrian geology of central Minnesota. Linear regression between the two data sets at each window position yields correlation, intercept, and slope parameters that quantitatively describe the relationship between the gravity and magnetic data and, in the case of the slope parameter, are often accurate estimates of magnetizatons‐to‐density ratios (MDR) of anomalous sources. In this study, gridded gravity and magnetic data from a 217.6 × 217.6 km area in central Minnesota were analyzed using a 8.5 × 8.5 km window. The study area includes part of the Early Proterozoic Penokean orogen and an Archean greenstone‐granite terrane of the Superior Province. The parameters derived by the moving‐window analysis show striking relationships to many geologic features, and many of the MDR estimates agree with rock property data. Inversely related gravity and magnetic anomalies are a characteristic trait of the Superior Province, but moving‐window analysis reveals that direct relationships occur locally. In the Penokean fold‐and‐thrust belt, gravity and magnetic highs over the Cuyuna range produce a prominent belt of large MDR estimates, which reflect highly deformed troughs of iron‐formation and other supracrustal rocks. This belt can be traced northeastward to sources that are buried by 3–5 km of Early Proterozoic strata in the Animikie basin. This configuration, in conjunction with recent geologic studies, indicates that the Animikie strata, which may represent foreland basin deposits associated with the Penokean orogen, unconformably overlie parts of the fold‐and‐thrust belt, and that earlier stratigraphic correlations between Cuyuna and Animikie strata are wrong. The results of this study indicate that moving‐window Poisson analysis is useful in the study of Precambrian terranes.

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Ali, Mohammed Y., Anthony B. Watts i Asam Farid. "Gravity anomalies of the United Arab Emirates: Implications for basement structures and infra-Cambrian salt distribution". GeoArabia 19, nr 1 (1.01.2014): 143–58. http://dx.doi.org/10.2113/geoarabia1901143.

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ABSTRACT Gravity measurements onshore and offshore of the United Arab Emirates (UAE) have been used to construct a new Bouguer gravity anomaly map of the region. The gravity data, which has been gridded at 2,700 m × 2,700 m interval, has been used to constrain the tectonic elements, major lineation trends and structures of the Neoproterozoic basement of the Arabian Plate and the distribution of infra-Cambrian salt basins. Advanced transformation techniques (including first vertical derivative, total horizontal derivative, tilt derivative and Euler deconvolution) were applied to identify gravity source edges as an aid to structural interpretation and geological modelling of the study area. Three major structural provinces (fold-and-thrust belt, foreland and salt tectonic provinces) were identified based on the residual Bouguer gravity anomaly field. The eastern fold-and-thrust belt province is associated with short-wavelength positive gravity anomalies, which are attributed to the allochthonous series of the Semail Ophiolite and its related thrust sheets. The central foreland basin province is characterised by NNW-oriented negative gravity anomalies associated with deepening of the basement and thickening of Aruma and Pabdeh sediments in the foredeep basins and flexure of the top and base of the crust by the load of the Semail Ophiolite. The western salt tectonic province displays well-defined local gravity lows superimposed on a regional gravity high, which probably reflects the swelling of infra-Cambrian salt above a shallowing of the basement and thinning of the foredeep sediments. In addition, gravity modelling constrained by seismic and well data indicates the presence of substantial infra-Cambrian salt bodies in all basins of the UAE both onshore and offshore including the southern area of the Rub’ Al-Khali Basin. An extensive array of previously unmapped N-S, NW- and SW-trending lineaments affecting the basement and possibly overlying sediments are mapped in the UAE. The N-S Arabian trending lineament represents the effect of a major structure, along which many important oilfields are located (e.g. Bu Hasa). The SW trend has regular spacing and is dominant in the southern and central part of Abu Dhabi, east of the Falaha syncline. The NW-SE lineament is the most striking and includes two well-defined trends that cross Abu Dhabi Emirate, which in this paper are named as the Abu Dhabi Lineaments. These lineaments are associated with a linear gravity high extending from the southwestern border with Oman to the offshore close to Zakum oilfield. They are probably related to the Najd Fault System.

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Bundesmann, Carsten, Christoph Eichhorn, Horst Neumann, Frank Scholze, Daniel Spemann, Michael Tartz, Hans J. Leiter, Roman Y. Gnizdor i Fabrizio Scortecci. "In situ erosion measurement tools for electric propulsion thrusters: triangular laser head and telemicroscope". EPJ Techniques and Instrumentation 9, nr 1 (8.02.2022). http://dx.doi.org/10.1140/epjti/s40485-022-00076-z.

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AbstractThe lifetime of electric propulsion (EP) thrusters depends particularly on the erosion characteristics of operation relevant components, for instance, the grid hole erosion of gridded ion thrusters or the channel wall erosion of Hall effect thrusters. Here two tools for in situ erosion measurements are presented, a triangular laser head for surface profiling and a telemicroscope for high-resolution optical imaging. Both can give access to radial and axial erosion parameters. The measurements can be done in situ without the need for breaking the vacuum and dismounting the thruster, which reduces thruster testing time considerably. In situ measurements can also help to ensure reproducibility of thruster performance conditions and can improve statistics of thruster characterization. The present work describes the fundamentals of both techniques in detail, selected experimental setups are presented, their performance is characterized and critically evaluated. The capabilities and limitations related to erosion measurements of EP thrusters are, exemplary, demonstrated for a gridded ion thruster RIT-22 and a Hall effect thruster SPT-100D.

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Jia-Richards, Oliver, i Trevor Lafleur. "Iodine Electric Propulsion System Thrust Validation: From Numerical Modeling to In-Space Testing". Journal of Propulsion and Power, 24.08.2023, 1–9. http://dx.doi.org/10.2514/1.b39198.

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In this paper, we complete a full-thrust audit of an iodine-based gridded ion thruster. Prior results have demonstrated excellent agreement between indirect and direct laboratory thrust estimates. Here, thrust estimates from numerical modeling, indirect laboratory testing from diagnostic probes and propulsion system telemetry, indirect in-space testing from onboard propulsion system telemetry, and direct in-space testing by analyzing orbital maneuvers are compared to demonstrate consistency between the four methods and complete the thrust audit. Results from recent in-space testing of the iodine-based thruster demonstrate that thrust estimates from all four methods agree to within three standard deviations of uncertainty for the 11 maneuvers studied. This thrust audit represents a critical step toward improving the understanding and technological maturity of iodine-based gridded ion thrusters for future mission applications, and it demonstrates the utility of recently developed in-space thrust inference techniques for analyzing low-thrust maneuvers.

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31

Chi, Zhemin, Yang Wang i Lin Cheng. "Indirect low-thrust trajectory optimization with gridded ion thruster model". Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, 1.10.2021, 095441002110438. http://dx.doi.org/10.1177/09544100211043846.

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The work deals with indirect optimization of minimum-time and minimum-fuel interplanetary trajectories when gridded ion thruster models are considered. Using an accurate model of solar electric propulsion is beneficial in preliminary mission design, and allows including operational constraints. The maximum thrust and the specific impulse are expressed as a function of thruster input power, which is achieved by means of point-fitting lines that match the performance capabilities of the thrusters. Minimum-time and minimum-fuel problems are formulated to be solved by indirect optimization. In order to increase the accuracy and robustness of the shooting procedure, analytic Jacobians are derived, and a hybrid switching detection technique is used to improve the integration accuracy for minimum-fuel problems. Two examples of Earth-to-Mars transfer and Near-Earth rendezvous mission using the realistic NASA’s Evolutionary Xenon Thruster (NEXT) are given to substantiate the feasibility and effectiveness of the proposed method.

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Zeng, Ming, Hui Liu, Hongyan Huang i Daren Yu. "Magnetic confinement less microwave discharge gridded ion thruster". Plasma Sources Science and Technology, 12.09.2023. http://dx.doi.org/10.1088/1361-6595/acf8ef.

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Abstract A watt-level microwave discharge is induced without magnetic confinement for a high-precision gridded ion thruster, making use of a coaxial transmission line resonator (CTLR). The thruster is characterized by performance measurements and plasma diagnosis, and a description of the operating mechanism of this thruster is given in this paper. A Faraday probe and a retarding potential analyzer are employed for the diagnosis. The results show that the plume divergence increases due to the electric field formed between the plume and the ion-induced electron emission cathode. A discharge mode transition is found during the increase of the microwave power, in which the bulk heating mode is converted to the surface heating mode. The magnetic-less microwave discharge gridded ion thruster performs a continuously adjustable thrust range of 5-115 μN and a highest total efficiency of 17.2%. Compared to the common ECR ion thruster, this thruster is free from magneto-static interference on the instruments and the additional magnetic momentum on the spacecraft.

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33

Eichhorn, Christoph, Lukas Pietzonka, Frank Scholze, Carsten Bundesmann, Daniel Spemann, Horst Neumann i Hans J. Leiter. "Single- and two-photon absorption laser-induced fluorescence spectroscopy in rare gases for gridded ion thruster diagnostics". EPJ Techniques and Instrumentation 9, nr 1 (7.03.2022). http://dx.doi.org/10.1140/epjti/s40485-022-00077-y.

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AbstractMethods based on laser-induced fluorescence spectroscopy are widely used for spatially resolved non-intrusive diagnostics of atomic or molecular densities and velocity distributions in plasma applications. With regard to electric space propulsion, one focus is on the investigation of rare gases such as xenon or krypton, which are currently the favored propellants in gridded ion- and Hall-effect thrusters. For gridded ion engines, diagnostics of neutral atoms is of interest since charge-exchange processes between neutrals and ions are the main driver of accelerator grid erosion, which limits the lifetime of a gridded ion thruster. Extending the capabilities of the advanced electric propulsion diagnostics platform which has been developed by the IOM and partners, single- and two-photon absorption laser-induced fluorescence diagnostics have been set-up recently at our institute. Both experimental set-ups, and as a series of first applications, measurements of krypton neutrals in the plume of the radiofrequency ion thruster RIT-10 (ArianeGroup GmbH), and xenon neutrals within the discharge chamber of a gridded radiofrequency ion source developed at IOM, are presented.

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Scholze, Frank, Fred Pietag, Harry Adirim, Matthias Kreil, Michael Kron, Ronny Woyciechowski, Carsten Bundesmann i Daniel Spemann. "Development and test of a cost-efficient gridded ion thruster propulsion system for small satellites – IonJet". Journal of Electric Propulsion 1, nr 1 (1.12.2022). http://dx.doi.org/10.1007/s44205-022-00028-5.

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AbstractIonJet is an engineering model of a low-cost electric propulsion system for small satellites. Whereas the flow control subsystem is based on the MICROJET 2000 system launched 2016 on the BIROS satellite, the thruster subsystem is based on a novel gridded ion thruster where the neutralizer is integrated in the ion thruster allowing for simultaneous ion and electron extraction. This design allows reducing the number of components and consequently costs and system complexity. The whole system was successfully tested under vacuum conditions regarding ignition and stable operation of the propulsion system. In the performance tests, thrusts of 1 mN could be achieved using Xe gas as propellant at a total power consumption of less than 50 W as well as specific impulses larger than 1000 s, including the gas consumption of the neutralizer. In addition, first tests with Kr gas were performed showing that for the same total power the achievable thrust is reduced to 55% – 68% of that for Xe.

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35

Saini, Vinod, i Rajaraman Ganesh. "Numerical simulation of an expanding magnetic field plasma thruster: a comparative study for argon, xenon and iodine fuel gases". Journal of Plasma Physics 90, nr 4 (sierpień 2024). http://dx.doi.org/10.1017/s0022377824000801.

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During a space mission, switching to an electric propulsion system from chemical propulsion, once the spacecraft is out of the Earth's gravity, significantly reduces the mission's overall cost. In electric propulsion, the Hall thruster and gridded ion thruster are established technologies. These thrusters compromise mission longevity due to continuous erosion of the device electrode material. To overcome this issue, an electrode less expanding magnetic field plasma thruster or helicon plasma thruster (HPT), was proposed and research is on going worldwide. The HPT shows scaling of thrust with input power while Hall thrusters and ion thrusters do not. Typically, an inert xenon gas is used as a fuel in HPT devices due to a low ionization potential and non-hazardous nature. Xenon is not easily available in nature and during a space mission it needs to be stored in high pressure tanks. Recently, iodine has been proposed as an alternate to xenon as it is easily available and does not have any storage issues. In most of the numerical simulations, argon is used as a fuel gas to reduce the simulation cost. Using a 1D3V particle-in-cell Monte Carlo collision code, we present here a net thrust generation for different fuel gases such as argon, xenon and iodine. We compare plasma flow rates and directed ion beam velocity for different fuel gases having identical inputs. Thrust and plasma flow are investigated for different magnetic field gradients in the plasma expansion region for unidirectional and bidirectional HPT and is reported here. Using iodine fuel, a significant increase in net thrust is obtained for higher magnetic field divergence for identical simulation input parameters while comparing with xenon fueled cases.

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Magaldi, Bernardo Vieira, Rodrigo Sávio Pessoa i Argemiro Soares da Silva Sobrinho. "A global model study of argon plasma chemistry used as propellant of a gridded ion thruster". Revista Brasileira de Aplicações de Vácuo 40, nr 1 (11.02.2021). http://dx.doi.org/10.17563/rbav.v40.1192.

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The search for new propulsion devices for corrections and adjustments in the orbits of space systems composed of constellations of satellites in specific arrangements has progressively increased with the growth of requests for data transmission with greater speed and capacity. Electric propulsion is the best solution to reduce the propellant mass, in addition to allowing long mission times. Among the various types of thrusters, electrostatic thrusters have a better-defined physics, making possible the development of computational models for the study and optimization of their operational parameters. A global model was develed for a cylindrical ion thruster with the inductively coupled plasma (ICP) generator originated by the circulation of a radio-frequency current in an inductive coil that surrounds the thruster, having at the output a polarized grid extraction system accelerating the ionized argon gas (propellant). The global model is formed by charged and neutral particle balance equations and energy equations of electrons and gas. Neutral and excited species are accelerated by drift out of the thruster and ionized species accelerated for the reason of the electric field generated by the pair of polarized grids in direct current. The most in-depth study of argon plasma chemistry found that, among the various parameters that interfere with species density, the number of excited species has a direct influence on ionization, although it does not interfere much with ion density, what can be translated into a higher rate ion replacement, which is extremely important to gain thrust and specific impulse.

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37

Vieira Magaldi, Bernardo, Rodrigo Sávio Pessoa i Argemiro Soares da Silva Sobrinho. "A global model study of argon plasma chemistry used as propellant of a gridded ion thruster". Revista Brasileira de Aplicações de Vácuo 40, nr 1 (11.02.2021). http://dx.doi.org/10.17563/rbav.v40i1.1192.

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The search for new propulsion devices for corrections and adjustments in the orbits of space systems composed of constellations of satellites in specific arrangements has progressively increased with the growth of requests for data transmission with greater speed and capacity. Electric propulsion is the best solution to reduce the propellant mass, in addition to allowing long mission times. Among the various types of thrusters, electrostatic thrusters have a better-defined physics, making possible the development of computational models for the study and optimization of their operational parameters. A global model was developed for a cylindrical ion thruster with the inductively coupled plasma (ICP) generator originated by the circulation of a radio-frequency current in an inductive coil that surrounds the thruster, having at the output a polarized grid extraction system accelerating the ionized argon gas (propellant). The global model is formed by charged and neutral particle balance equations and energy equations of electrons and gas. Neutral and excited species are accelerated by drift out of the thruster and ionized species accelerated for the reason of the electric field generated by the pair of polarized grids in direct current. The most in-depth study of argon plasma chemistry found that, among the various parameters that interfere with species density, the number of excited species has a direct influence on ionization, although it does not interfere much with ion density, what can be translated into a higher rate ion replacement, which is extremely important to gain thrust and specific impulse.

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Takahashi, Kazunori. "Thirty percent conversion efficiency from radiofrequency power to thrust energy in a magnetic nozzle plasma thruster". Scientific Reports 12, nr 1 (10.11.2022). http://dx.doi.org/10.1038/s41598-022-22789-7.

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AbstractInnovations for terrestrial transportation technologies, e.g., cars, aircraft, and so on, have driven historical industries so far, and a similar breakthrough is now occurring in space owing to the successful development of electric propulsion devices such as gridded ion and Hall effect thrusters, where solar power is converted into the momentum of the propellant via acceleration of the ionized gases, resulting in a high specific impulse. A magnetic nozzle (MN) radiofrequency (rf) plasma thruster consisting of a low-pressure rf plasma source and a MN is an attractive candidate for a high-power electric propulsion device for spacecraft, as it will provide a long lifetime operation at a high-power level due to the absence of an electrode exposed to the plasma and a high thrust density. The high-density plasma produced in the source is transported along the magnetic field lines toward the open-source exit and the plasma is then spontaneously accelerated in the MN. By ejecting the plasma flow from the system, the reaction forces are exerted to the thruster structure including the source and the MN, and the spacecraft is resultantly propelled. The thruster will open the next door for space technologies, while the performance of the MN rf plasma thruster has been lower than those of the mature electric propulsion devices due to the energy loss to the physical walls. Here the thruster efficiency of about 30%, being the highest to date in this type of thruster, is successfully obtained in the MN rf plasma thruster by locating a cusp magnetic field inside the source, which acts as a virtual magnetic wall isolating the plasma from the source wall. The increase in the thrust by the cusp can be explained by considering the reductions of the loss area and the plasma volume in a thrust analysis combining a global source model and a one-dimensional MN model.

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39

Conde, L., J. Gonzalez, J. M. Donoso, J. L. Domenech-Garret i M. A. Castillo. "Thrust measurements and mesothermal plasma plume of the Alternative Low Power Hybrid Ion Engine (alphie)". Journal of Electric Propulsion 1, nr 1 (14.11.2022). http://dx.doi.org/10.1007/s44205-022-00027-6.

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AbstractThe high specific impulse Alternative Low Power Ion Engine (alphie) is a gridded plasma thruster different from conventional (Kaufman) ion engines. In this disruptive concept, the ionization of the propellant neutral gas and the neutralization of ion outflow is achieved with only one cathode located in front and outside of the thruster. Electrons and ions move under the self-consistent field created by the DC voltage applied to its two planar grids together with the currents of charges flowing through them, unlike to conventional ion engines, where only ions move through its ion optics system. The stationary mesothermal flow of ions and electrons in the plasma plume is characterized with a retarded field energy analyzer in conjunction with Langmuir and emissive probes. The ion velocity distribution functions and the electron energy spectra for different operating conditions of the alphie thruster are discussed. The observed high ion temperatures are explained by the collisional interaction between the fast ionizing electrons and the neutral atoms that increases their average kinetic energy. Finally, the alphie delivers 0.8-3.5 mN throttleable thrusts giving specific impulses in the range of 14000-20000 s with estimated thruster efficiencies between 8% and 40%.

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Becker, Felix, Pascal Sarnoch, Kristof Holste, Hans Leiter i Peter J. Klar. "Determining the 2D spatial distribution of plasma parameters in a cylindrical cross section of a radio-frequency ion thruster by optical emission spectroscopy". Journal of Electric Propulsion 4, nr 1 (27.02.2025). https://doi.org/10.1007/s44205-025-00112-6.

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Abstract Gridded ion engines, such as the radio-frequency ion thruster, are highly efficient designs for generating thrust on satellites or spacecrafts for both commercial and scientific missions, due to the very high exhaust velocities achieved. A thorough understanding of the low-temperature and low-pressure plasma parameters is essential in order to characterize, design, and optimize such a thruster. Corresponding plasma parameters can be obtained non-invasively from empirical correlations between the results of Langmuir double probe measurements and optical emission spectroscopy. The plasma parameters can be extracted solely from the recorded optical emission spectra once such an empirical correlation is established for a specific experimental setup and various operation conditions. Light from an object plane at a specified depth within the plasma is focussed onto the projection plane, using a telescopic arrangement of lenses and an aperture. Despite being out of focus, the grid structure is still identifiable though slightly blurred. By carefully scanning across this image, taking spectra at every light spot, we can record a series of optical emission spectra where each spectrum corresponds to a plasma volume located in the object plane behind a grid hole. The object plane is a 2D cross section within the bulk of the plasma at a distance of 5 cm behind the grid. Our approach therefore allows us to monitor the spatial profiles of plasma parameters in this cross section of the RIT 10 for different operating points of the thruster. Such spatial profiles are essential for characterizing thruster performance and improving global modeling of such thrusters. We believe that this method is also applicable for RITs of other sizes in the context of space qualification.

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Foster, John E., i Tyler J. Topham. "A review of the impact of ground test-related facility effects on gridded ion thruster operation and performance". Physics of Plasmas 31, nr 3 (1.03.2024). http://dx.doi.org/10.1063/5.0173655.

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A key consideration in the interpretation of ground test data of electric propulsion devices purposed for spaceflight is understanding how facility-effects influence thruster operation. This understanding is critical to the prediction of actual thruster performance in space. The necessity of science-based predictions gleaned from ground tests are particularly critical at higher thruster power levels. Operation of engines at higher power levels in vacuum chambers leads to considerable elevation in background pressure, background plasma density, and backsputter rates. This review examines the influence of ground test facility effects on gridded ion thruster operation. Ground test operation is compared with flight data, where available, to obtain a clear picture of operational differences. Mitigation strategies to alleviate facility effects are also commented upon.

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42

Nishii, Keita, i Deborah A. Levin. "Three-Dimensional Kinetic Simulations of Carbon Backsputtering in Vacuum Chambers from Ion Thruster Plumes". Journal of Propulsion and Power, 4.10.2023, 1–15. http://dx.doi.org/10.2514/1.b39194.

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Gridded ion thrusters are tested in ground vacuum chambers to verify their performance when deployed in space. However, the presence of high background pressure and conductive walls in the chamber leads to facility effects that increase uncertainty in the performance of the thruster in space. To address this issue, this study utilizes a fully kinetic simulation to investigate the facility effects on the thruster plume. The in-chamber condition shows a downstream neutral particle density 100 times larger than the in-space case due to ion neutralization at the wall and limited vacuum pump capability, resulting in a significant difference in the density and distribution of charge-exchange ions. The flux, energy, and angle of charge-exchange ions incident on the chamber wall are found to be altered by the electron sheath, which can only be simulated by the fully kinetic approach, as opposed to the conventionally used quasi-neutral Boltzmann approach. We also examine the effect of backsputtering, another important facility effect, and find that it does not necessarily require a fully kinetic simulation as the incident flux and energy of the sampled charge-exchange ion are negligibly small. Finally, we demonstrate that the carbon deposition rate on the thruster is significantly influenced by the angular dependence of the sputtered carbon, with a nearly 50% effect.

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Ramasamy, Sai Vigness, i Leonid Bazyma. "Application of iodine plasma for electric propulsion". Aerospace Technic and Technology, nr 4sup1 (29.08.2024). http://dx.doi.org/10.32620/aktt.2024.4sup1.10.

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Most state-of-the-art electric space propulsion systems, such as gridded and Hall effect thrusters, use xenon as the propellant gas. However, xenon is very rare and expensive to produce, and it is used in a number of competing industrial applications. Iodine is emerging as an attractive alternative to xenon in several electric propulsion technologies. Its lower cost and larger availability, solid state at standard temperature and pressure, its low vapor pressure and its low ionization potential make it an attractive option. Attempts to implement an alternative to xenon propellants (Iodine, O2 , N2 , H2 , CO2 etc) in conventional propulsion systems have been met with measured success. However, the use of chemically reactive species, such as O2, H2, or iodine, requires the chosen propulsion platform to be chemically compatible with the propellant. Significant reductions in the operational lifetime of the thruster because of chemical incompatibility negates any potential increase in thruster performance or propellant availability. Thus, careful material selection for the electric propulsion system itself and for the components employed on the satellite is required in the light of a typical space mission duration of several years. Due to the more complex reaction processes and energy loss channels in iodine plasma´s however, as well as the historical lack of reliable collision cross-section data, the development of accurate theoretical and numerical models has been hindered. The development of techniques that can be applied to chemically dissimilar propellants, focusing on electromagnetic behaviour, would represent a significant improvement in the state of discharge characterization and thruster analysis. In this work, we conducted a comparative analysis of the existing modeling results for various types of electric propulsion using iodine as a propellant gas, as well as the results of experiments with iodine plasma with an emphasis on the thrust-to-power ratio.

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44

Bräumer, Kalle, Rodrigo Sandoval Rodriguez, Markus Stein, Konstantin Keil, Kristof Holste, Felix Becker, Jana Zorn, Konrad Wehkamp, Sangam Chatterjee i Peter J. Klar. "Validating THz time-domain spectroscopy as a tool for characterizing low pressure inductively coupled plasmas of ion thrusters". Journal of Electric Propulsion 4, nr 1 (25.02.2025). https://doi.org/10.1007/s44205-025-00106-4.

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Abstract Accurate characterization of plasmas within the discharge chambers of gridded ion engines is essential for their advancement. This study showcases the effectivity of terahertz time-domain spectroscopy (THz-TDS) as a non-invasive technique for profiling low-pressure inductively coupled plasmas, mimicking the conditions of the discharge chamber in a radio-frequency ion thruster. Operating at pressures of 3 - $$7\cdot 10^{-3}$$ 7 · 10 - 3 mbar inside the discharge chamber and a supply power of the radio frequency generator ranging from 10 - 80 W, THz-TDS reveals electron densities in the range of $$2\cdot 10^{16}$$ 2 · 10 16 - $$2\cdot 10^{17}$$ 2 · 10 17 m $$^{-3}$$ - 3 for xenon, krypton, and argon plasmas. Our results show good agreement with Langmuir probe measurements and global plasma modeling, highlighting the accuracy and reliability of THz-TDS. This validation, conducted under conditions representative of gridded ion engines, demonstrates that THz-TDS is, in principle, suitable for characterizing the electron system of the plasma ignited in such thrusters in operation. This offers great potential of developing a promising additional tool for plasma diagnostics in electric propulsion systems.

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Lafleur, Trevor, Lui Habl, Elena Zorzoli Rossi i Dmytro Rafalskyi. "Development and validation of an iodine plasma model for gridded ion thrusters". Plasma Sources Science and Technology, 17.10.2022. http://dx.doi.org/10.1088/1361-6595/ac9ad7.

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Abstract Iodine is emerging as an attractive alternative propellant to xenon for several electric propulsion technologies due to its significantly lower cost and its ability to be stored unpressurized as a solid. Because of the more complex reaction processes and energy-loss channels in iodine plasmas however, as well as the historical lack of reliable collision cross-section data, the development of accurate theoretical and numerical models has been hindered. Using recently calculated theoretical cross-sections, we present an iodine plasma model and perform a comparison with experimental data obtained from an iodine-fuelled gridded ion thruster. The model is in reasonable agreement with experimental measurements of the ion beam current, propellant mass utilization efficiency, and ion beam composition, and is able to quantitatively and qualitatively reproduce system behaviour as the input mass flow rate and RF power are varied. In addition, both the model and experiment show that the use of iodine can lead to a performance enhancement when compared with xenon. This occurs because of the combination of different iodine reaction processes, collision cross-section values, and inelastic energy thresholds which result in lower collisional energy losses, as well as an increased antenna-plasma power transfer efficiency for thrusters using a radio-frequency inductive coil.

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Guaita, Matteo, Alberto Marín-Cebrián, Mario Merino, Eduardo Ahedo, Fabrice Cipriani i Kathe Dannenmayer. "Electron populations and neutralization process in the plume of a gridded ion thruster". Plasma Sources Science and Technology, 24.03.2025. https://doi.org/10.1088/1361-6595/adc482.

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Abstract In order to assess the importance of collisional processes in the neutralization of a gridded ion thruster plume this study presents a series of simulations carried out with a planar, full-PIC code provided of a library of electron, ion and neutral collisions. In particular, we find that the inclusion of electron inelastic collisions, such as ionization and excitation, results fundamental in the generation of a population of electrons trapped in the plume's potential well, which play a major role in the neutralization of the plume and in the formation of the electric potential map. A further investigation is therefore carried out on the properties of the electron populations present in the plume, suggesting that the trapped population results mostly insensitive to the emission properties of the cathode, but displays a strong dependence on the inclusion of inelastic collisions and a slow approach to stationary conditions dictated by the timescales of these collisions. Given the symmetry of the plume bulk even in presence of an externally mounted cathode, we further extend the study to an axisymmetric simulation case with an annular cathode, that allows the evaluation of a three-dimensional expansion process. The build up of the trapped electron population in this case is even slower, because of the smaller neutral density observed when expanding the plume in three dimensions, and an acceleration strategy that speeds-up the approach to steady state without altering it is therefore proposed. Nevertheless, the main governing physical processes observed in the planar case remain prominent also in this latter case.

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47

Nishii, Keita, i Deborah A. Levin. "Kinetic simulation of ion thruster plume neutralization in a vacuum chamber". Plasma Sources Science and Technology, 31.10.2023. http://dx.doi.org/10.1088/1361-6595/ad0836.

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Abstract The electrical environment of a ground vacuum testing chamber creates facility effects for gridded ion thrusters. For example, it is well known that the plume from the thruster generates current paths that are very different from what occurs in space, and the neutralization of this plume is also different. For reasons such as this, it is important to clarify how the experimental testing environment affects plasma flows, but understanding this effect solely through ground experiments is difficult. To that end, this study utilizes particle-in-cell and direct simulation Monte Carlo methods to simulate xenon beam ions and electrons emitted from a neutralizer. First, we compare simulations conducted within the chamber to those conducted in space, demonstrating that grounded chamber walls increase the electric potential and electron temperature. Next, we investigate the impact of the neutralizer's position and the background pressure on the plume in the vacuum chamber. We find that as the neutralizer position moves closer to the location of maximum potential, more electrons are extracted, resulting in increased neutralization of the plume. We also observe that high background pressure generates slow charge-exchange ions, creating ion sheaths on the side walls that alter ion current paths. Finally, we discuss how the potential at the thruster and neutralizer exits affects the plume. The relative potential of the neutralizer to the vacuum chamber wall is observed to significantly influence the behavior of the electrons, thereby altering the degree of plume neutralization. These findings are shown to be consistent with experimental results in the literature and demonstrate the promise of high-performance simulation.

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Yang, Zhi, Honghui Guo, Jinwei Bai, Yang Li, Yong Cao i Yu Zhu. "Experimental study of a neutralizer-free gridded ion thruster using radio-frequency self-bias effect". Plasma Science and Technology, 8.11.2022. http://dx.doi.org/10.1088/2058-6272/aca13f.

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Abstract An experimental study on the quasi-neutral beam extracted by a neutralizer-free gridded ion thruster prototype was presented. The prototype was designed using an inductively coupled plasma (ICP) source terminated by a double-grid accelerator. The beam characteristics were compared when the accelerator was radio-frequency (RF) biased and direct-current (DC) biased. An RF power supply was applied to the screen grid via a blocking capacitor for the RF acceleration, and a DC power supply was directly connected to the screen grid for the DC acceleration. Argon was used as the propellant gas. Furthermore, the characteristics of the plasma beam, such as the floating potential, the spatial distribution of ion flux, and the ion energy distribution function (IEDF) were measured by a four-grid retarding field energy analyzer. The floating potential results showed that the beam space charge is compensated in the case of RF acceleration without a neutralizer, which is similar to the case of classical DC acceleration with a neutralizer. The ion flux of RF acceleration is 1.17 times higher than that of DC acceleration under the same DC component voltage between the double-grid. Moreover, there are significant differences in the beam IEDFs for RF and DC acceleration. The IEDF of RF acceleration has a widened and multi-peaked profile, and the main peak moves toward the high-energy region with increasing the DC self-bias voltage. In addition, by comparing the IEDFs with RF acceleration frequencies of 3.9 MHz and 7.8 MHz, it is found that the IEDF has a more centered main peak and a narrower energy spread at a higher frequency.

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Dobkevicius, Mantas, i Davar Feili. "A coupled performance and thermal model for radio-frequency gridded ion thrusters*". European Physical Journal D 70, nr 11 (listopad 2016). http://dx.doi.org/10.1140/epjd/e2016-70273-7.

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Nono, Ayumu, Takato Morishita, Satoshi Hosoda, Ryudo Tsukizaki i Kazutaka Nishiyama. "Effect of spacecraft surface conductivity on voltage of microwave neutralizer in gridded ion thrusters". Acta Astronautica, sierpień 2023. http://dx.doi.org/10.1016/j.actaastro.2023.07.045.

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