Thruster Model Research Articles

Wind tunnel testing and performance modeling of an atmospheric ion thruster

Abstract In this work a complete atmospheric electro–hydro-dynamic (EHD) thruster is tested in a subsonic wind tunnel, with the purpose of evaluating changes in performance due to simulated flight conditions and, for the first time, comparing them with a physical model of the drift region. An aerodynamic frame was designed to accommodate the electrodes inside the wind tunnel. Propulsive force and electrical measurements were conducted to assess performance exploiting dimensionless coefficients derived from one-dimensional theory. The results, on top of validating the theory, show how EHD thrusters can operate with a non-zero bulk velocity and highlight the importance of optimized frames and electrodes to enhance the capabilities of flying demonstrators. The test campaign revealed that the operating voltage envelope extends with increasing bulk velocity, leading to an increase in maximum thrust.

Simulation analysis and hydrodynamic performance optimization of small MHD thruster based on improved I-bridge structure

Abstract Magnetic hydrodynamic drive (MHD) generates thrust by the coupling interaction of three fields: flow field-electric field-magnetic field. Because this propulsion method has no propeller or mechanical structure, it has the advantages of quiet, simple structure, easy operation, flexible layout, and difficult to detect. This is the current research hot spot. In order to meet the needs of miniaturized silent propulsion, this paper selects a linear internal magnetic thruster for research and analysis and improves the design of an I-shaped magnetic bridge structure. Firstly, the thrust and efficiency of the thruster under ideal conditions are calculated, and the thruster model is established. The conclusion is that the I-shaped magnetic bridge can increase the magnetic field intensity of the channel and significantly improve the MHD propulsion efficiency. At the same time, it is found that MHD thruster can reduce noise during operation, but the current required for propulsion is large, and seawater electrolysis will occur, which has a certain impact on the environment. Finally, the problems of small direct drive MHD propulsion are analyzed, and the future development direction of MHD propulsion is prospected.

Hall thruster model improvement by multidisciplinary uncertainty quantification

We study the analysis and refinement of a predictive engineering model for enabling rapid prediction of Hall thruster system performance across a range of operating and environmental conditions and epistemic and aleatoric uncertainties. In particular, we describe an approach by which experimentally-observed facility effects are assimilated into the model, with a specific focus on facility background pressure. We propose a multifidelity, multidisciplinary approach for Bayesian calibration of an integrated system comprised of a set of component models. Furthermore, we perform uncertainty quantification over the calibrated model to assess the effects of epistemic and aleatoric uncertainty. This approach is realized on a coupled system of cathode, thruster, and plume models that predicts global quantities of interest (QoIs) such as thrust, efficiency, and discharge current as a function of operating conditions such as discharge voltage, mass flow rate, and background chamber pressure. As part of the calibration and prediction, we propose a number of metrics for assessing predictive model quality. Based on these metrics, we found that our proposed framework produces a calibrated model that is more accurate, sometimes by an order of magnitude, than engineering models using nominal parameters found in the literature. We also found for many QoIs that the remaining uncertainty was not sufficient to account for discrepancy with experimental data, and that existing models for facility effects do not sufficiently capture experimental trends. Finally, we confirmed through a global sensitivity analysis the prior intuition that anomalous transport dominates model uncertainty, and we conclude by suggesting several paths for future model improvement. We envision that the proposed metrics and procedures can guide the refinement of future model development activities.

Thrust of a pulsed plasma jet measured from deviations of a ballistic pendulum

We measured the peak force of the plasma jet produced by a pulsed coaxial plasma gun operated at voltages up to 2 kV, using a home-made ballistic pendulum positioned in two locations, one in the proximity of the gun nozzle at 0.75 cm and the second at a distance of 9 cm from the gun nozzle. The force of the plasma wind is inferred and ranges from 11 to 60 N, which is almost an order of magnitude higher than that of typical ion-based thrusters. The results of various models of self-field magneto-plasmadynamic thrusters indicate that the magnetic component thrust tends to dominate over the thermal expansion, particularly at higher discharge voltages of 1.5 kV and 2 kV. The highest thrust of 60 N is obtained for a 2 kV discharging voltage. The plasma was ignited in CO2 at pressures between 1 and 5 Torr. The displacement of the pendulum pushed by the plasma wind force was measured using a high-speed camera.

Multi-hole grid thruster plume simulation model based on single grid aperture analytical model

This paper presents a plume divergence angle prediction model for ion thruster. Firstly, an analytical model using Gaussian distribution for single grid hole plume is proposed. The parameters of this single hole model are obtained from the particle simulation results of ion optics which utilizes the immersed finite element Particle-in-cell Monte Carlo collision (IFE-PIC-MCC) method. Then, by the extension of the single hole model, a three-dimensional plume model for the whole ion optics is proposed. This plume model can be used to predict the divergence angle of ion thruster plume. Finally, a numerical example with the simulation of a 217-hole ion optics is provided to demonstrate the features of the proposed method.

Modelling a thrust imparted by a highly ionized magnetic nozzle rf plasma thruster

Influence of the local-ionization-induced neutral depletion on the thrust imparted by the magnetic nozzle plasma thruster is discussed by simply considering reduction of the neutral density due to the ionization in the thruster model combining the global source model and the one-dimensional magnetic nozzle model. When increasing the rf power, it is shown that the increase rate of the plasma density is reduced, while the electron temperature continues to increase due to a decrease in the neutral density. Since the major components of the thrust are originated from the electron pressures in the source and in the magnetic nozzle, the increase in the electron temperature contributes to the increase in the thrust in addition to the gradual density increase by the rf power. The model qualitatively predicts the reduction of the thruster efficiency by the neutral depletion for the high-power condition, compared with the constant neutral density model.

An introduction to electric thruster modeling for stratospheric airship

An introduction to electric thruster modeling for stratospheric airship

Comparison Study of the k − kL − ω and γ − Reθ Transition Model in the Open-Water Performance Prediction of a Rim-Driven Thruster

The present work examines the capabilities of two transition models implemented in ANSYS Fluent in the open-water performance prediction of a rim-driven thruster (RDT). The adopted models are the three-equation k−kL−ω and the four-equation γ−Reθ models. Both of them are firstly tested on a ducted propeller. The numerical results are compared with available experimental data, and a good correlation is found for both models. The simulations employing two transition models are then carried out on a four-bladed rim-driven thruster model and the results are compared with the SST k−ω turbulence model. It is observed that the streamline patterns on the blade surface are significantly different between the transition and fully turbulent models. The transition models can reveal the laminar region on the blade while the fully turbulent model assumes the boundary layer is entirely turbulent, resulting in a considerable difference in torque prediction. It is noted that unlike the fully turbulent model, the transition models are quite sensitive to the free-stream turbulence quantities such as turbulent intensity and turbulent viscosity ratio, as these quantities determine the onset of the transition process. The open-water performance of the studied RDT and resolved flow field are also presented and discussed.

Квантово-механическая модель ионного двигателя малого космического аппарата

The article presents a quantum mechanical model of an ion thruster. The basic equations describing the shape of the accelerated beam are considered. Detector plates demonstrating the interference pattern in thin films are presented. A mathematical description of the relief of thin films is given using the resulting wave function. The operation of a low-power ion engine is demonstrated. The results of numerical solution of the model with different initial values are shown. Based on the results of calculations, diagrams of the trajectories of charged particles are constructed.

Experimental investigation on magnetic field strength providing thrust saturation in a magnetic nozzle radiofrequency plasma thruster

Magnetic field strength applied to a magnetic nozzle radiofrequency (rf) plasma thruster having a 10.5 cm diameter source tube is increased up to about 3 kG by pulsing the solenoid current. A target plate is installed at 30 cm downstream of the source and an impulse bit exerted to the target is measured to assess the thrust, where the thrust balance measurement was impossible due to the interaction between the pulsed magnetic fields and the eddy currents on surroundings. Since the diameter of the plasma plume at the target location is larger than the target diameter, a comparison between the thrust balance and target measurements under continuous magnetic field and rf power is performed prior to the pulsed magnetic field experiments, showing that about 65 percent of the plasma momentum is exerted to the target plate. Saturation of the impulse bit, being equivalent to the force multiplied by the rf pulse width, is clearly observed when increasing the magnetic field strength. The magnetic field providing the force saturation is found to be changed by the source diameter, which is qualitatively explained by considering a change in the plasma loss to the source wall in a thruster model containing the particle balance, power balance, and one-dimensional magnetic nozzle models. It is suggested that the magnetic field strength required for optimizing the force, i.e. the thrust, can be reduced when enlarging the source tube diameter.

Plasma plume simulation of an atomic oxygen-fed ion thruster in very-low-earth-orbit

The plasma plume flow of an atomic oxygen-fed (AO-fed) ion thruster is numerically investigated as a simplification of the atmosphere-breathing electric propulsion (ABEP). A predictive analysis is conducted focusing on the ion backflow phenomenon and plume-background interaction in very-low-earth-orbit (VLEO). The computational framework employs two sequentially integrated numerical methods: a zero-dimensional (0-D) analytical model for the radio-frequency ion thruster and a hybrid method of the particle-in-cell (PIC) and direct simulation Monte Carlo (DSMC) techniques. The 0-D analytic model is employed for the prediction of exhaust conditions, while the hybrid PIC-DSMC method adopts these predictions to conduct the plasma plume simulations. A generalized collision cross-section model is introduced to enable consistent kinetic simulations for both AO and xenon propellants in VLEO atmosphere. The plasma plume simulations are conducted in an axisymmetric domain, including a cylindrical satellite body to consider wake flow. The exhaust ions exhibit diffusive transport transverse to the ion beam direction, implying the ion backflow. The backflowing ion current density can be increased in AO-fed thrusters, which require a high propellant flow rate to achieve a practical thrust. The AO-fed ion thruster shows a more active interaction between its plasma plume and the VLEO atmosphere compared to conventional xenon-based thrusters. The intensified plume-background interaction modifies the backflowing ion current density and the kinetic energy of individual ions, factors related to the spacecraft’s surface contamination.

An integrative mathematical model of microwave ion thruster for mHz-frequency thrust noise analysis

Many high-precision space missions need thrusters to produce thrust with low noise to compensate for disturbances and ensure satellite platform stability. Microwave ion thruster is characterized with a wide thrust range and potential for these missions. A cost-effective and accurate mathematical model is crucial for mHz-frequency thrust noise analysis and feedback controller design. The Particle-In-Cell (PIC) and global models are two common simulation tools. The PIC model is characterized with high accuracy but huge computation cost, which is difficult to analyze long-time performance characteristics. Now, the global model is only used for the discharge chamber with low accuracy and cannot reflect ion extraction properties. In this paper, an integrative mathematical model is built for a 1-cm microwave ion thruster and can reflect ion beamlet divergence and impingement on the Accelerator Grid (AG). Simulation results show good agreement with experiments at 0.06 sccm. However, the model demonstrates worse consistency with experiments when the flux increases to 0.1 sccm, which may be because the influence of neutral gas on the Electron Cyclotron Resonance (ECR) is not considered in the model. A long-time (1000 s) simulation is conducted with this model under 35 μN. It takes 3 hrs, and the thrust noise reaches 1 μN/Hz0.5 at 1 mHz.

Coupling Dynamics and Three-Dimensional Trajectory Optimization of an Unmanned Aerial Vehicle Propelled by Electroaerodynamic Thrusters

Electroaerodynamic unmanned aerial vehicles (EAD-UAVs) are innovative UAVs that use high-voltage asymmetric electrodes to ionize air molecules and Coulomb force to push these ions to produce thrust. Unlike fixed-wing and rotor UAVs, EAD-UAVs contain no moving surfaces and have the advantages of very low noise, low mechanical fatigue, and no carbon emissions. This paper proposes an EAD-UAV configuration with an orthogonal arrangement of multiple EAD thrusters to adjust the EAD-UAV attitude and flight trajectory through voltage distribution control alone. Based on a one-dimensional dynamic model of an EAD thruster, the attitude–path coupling dynamics of the EAD-UAV were derived. To achieve EAD-UAV flight control for a specified target, the Bezier shaping approach (BSA) was implemented to realize rapid trajectory optimization considering the coupling dynamic constraints. The numerical simulation results indicate that the BSA can quickly procure an optimized flight trajectory that satisfies the dynamic and boundary constraints. Compared with the Gaussian pseudospectral method (GPM), the BSA changes the optimization index of the objective function by nearly 1.14% but demands only nearly 1.95% of the computational time on average. Hence, the improved integrative Bezier shaping approach (IBSA) can overcome the poor convergence issue of the BSA under the continuous acceleration constraint of multi-target flight trajectories.

Stable nullspace adaptive parameter identification of 6 degree-of-freedom plant and actuator models for underactuated vehicles: Theory and experimental evaluation

Model-based approaches to navigation, control, and fault detection that utilize precise nonlinear models of vehicle plant dynamics will enable more accurate control and navigation, assured autonomy, and more complex missions for such vehicles. This paper reports novel theoretical and experimental results addressing the problem of parameter estimation of plant and actuator models for underactuated underwater vehicles operating in 6 degrees-of-freedom (DOF) whose dynamics are modeled by finite-dimensional Newton-Euler equations. This paper reports the first theoretical approach and experimental validation to identify simultaneously plant-model parameters (parameters such as mass, added mass, hydrodynamic drag, and buoyancy) and control-actuator parameters (control-surface models and thruster models) in 6-DOF. Most previously reported studies on parameter identification assume that the control-actuator parameters are known a priori. Moreover, this paper reports the first proof of convergence of the parameter estimates to the true set of parameters for this class of vehicles under a persistence of excitation condition. The reported adaptive identification (AID) algorithm does not require instrumentation of 6-DOF vehicle acceleration, which is required by conventional approaches to parameter estimation such as least squares. Additionally, the reported AID algorithm is applicable under any arbitrary open-loop or closed-loop control law. We report simulation and experimental results for identifying the plant-model and control-actuator parameters for an L3 OceanServer Iver3 autonomous underwater vehicle. We believe this general approach to AID could be extended to apply to other classes of machines and other classes of marine, land, aerial, and space vehicles.

Computational fluid dynamic study on design and modification of underwater remotely operated vehicle

Remotely Operated Vehicle (ROV) has been widely used in numerous underwater exploration applications such as exploration of complex deep sea environment, pipeline detection, installation, maintenance, and repair. Thus, it is worthy to design, optimize, and performance evaluation of ROV systems for underwater exploration purposes. Computational Fluid Dynamic (CFD) is a computational approach that is very helpful and widely used to examine the flow characteristics of ROV systems. In this research work, CFD analyses of ROV bodies with different thruster blades were carried out in order to generate thrust forces by the thruster blades. For this purpose, ANSYS FLUENT was used to examine the flow characteristics over the ROV body. The analyses were performed at different flow velocities, such as 1 m/s, 1.5 m/s, 2 m/s, 2.5 m/s, 3 m/s and 3.5 m/s. The outcomes were in the form of thrust force, drag force, pressure distribution, and velocity distribution. The result shows that four-blade thruster generates maximum thrust force as compare to other ROV thruster models. The main reason behind this higher thrust force is due to the larger motion of the fluid. Similarly, drag force was also investigated and observed that the drag force is greater for thruster model 3, having four blades due to the large frontal area of the ROV body and thruster blades. The results obtained in this study are very helpful for engineers and researchers to design and optimize ROV models using numerical methods.

Development of minimalistic propulsion system for university nanosatellite

The paper presents the results of development of a neutralizer-free high-frequency ion thruster for university nanosatellite propulsion systems which allow it to perform orbit correction tasks. The application of high-frequency ion thruster technologies allows the self-neutralization mode and is relevant for the development of engines for CubeSat format small satellites where the size and weight of the propulsion system must be as minimal as possible. A pair of shapes of neutralizer-free high-frequency ion thrusters with different accelerating region geometries are proposed. The analysis of plasma flow and the charged particles acceleration was carried out. The trajectory and acceleration of a quasi-neutral plasma flow was calculated for crossed electric and magnetic fields. The cyclotron resonance model was applied for the quasi-neutral plasma flow acceleration in an ambipolar field. The coaxial structure of the ion thruster model is discussed. Preliminary estimate of the performance of the propulsion system prototype was carried out for a pulsed operation mode. Additionally, the energy budget of a high-frequency ion thruster prototype was calculated.

Design analysis and optimisation of an integrated motor pump-jet thruster with improved resistance to cavitation

ABSTRACT In order to meet the basic design requirements for high critical speed met, and anti-cavitation performance enhanced of Integrated Motor Pump-Jet (IMP) thrusters, a three-dimensional model of the IMP thruster using the blade parameter three-dimensional (3D) inverse design method was developed. The model utilises the shear stress transport (SST) turbulence model and the Zwart–Gerber–Belamri (Z-G-B) cavitation model. Then, based on the non-dominated ranking genetic algorithm and multi-objective parameter seeking theory to improve the IMP thruster's cavitation improvement optimization design. After optimisation, the hydrodynamic performance and anti-cavitation performance of the rotor blades were slightly improved. In order to further carry out the design of anti-cavitation performance, the oblique flow is introduced to further analyse according to the influence mechanism. The main focus was on the IMP thruster's excitation force, pulsation pressure and velocity distribution, the oblique flow angle had less impact than the cavitation number in the oblique flow field.

A Coaxial Pulsed Plasma Thruster Model with Efficient Flyback Converter Approaches for Small Satellites

Pulsed plasma thrusters (PPT) have demonstrated enormous potential since the 1960s. One major shortcoming is their low thrust efficiency, typically <30%. Most of these losses are due to joule heating, while some can be attributed to poor efficiency of the power processing units (PPUs). We model PPTs to improve their efficiency, by exploring the use of power electronic topologies to enhance the power conversion efficiency from the DC source to the thruster head. Different control approaches are considered, starting off with the basic approach of a fixed frequency flyback converter. Then, the more advanced critical conduction mode (CrCM) flyback, as well as other optimized solutions using commercial off-the-shelf (COTS) components, are presented. Variations of these flyback converters are studied under different control regimes, such as zero voltage switching (ZVS), valley voltage switching (VVS), and hard switched, to enhance the performance and efficiency of the PPU. We compare the max voltage, charge time, and the overall power conversion efficiency for different operating regimes. Our analytical results show that a more dynamic control regime can result in fewer losses and enhanced performance, offering an improved power conversion efficiency for PPUs used with PPTs. An efficiency of 86% was achieved using the variable frequency approach. This work has narrowed the possible PPU options through analytical analysis and has therefore identified a strategic approach for future investigations. In addition, a new low-power coaxial micro-thruster model using equivalent circuit model elements is developed.This is referred to as the Carlow–Stuttgart model and has been validated against experimental data from vacuum chamber tests in Stuttgart’s Pulsed Plasma Laboratory. This work serves as a valuable precursor towards the implementation of highly optimized PPU designs for efficient PPT thrusters for the next PETRUS (pulsed electrothermal thruster for the University of Stuttgart) missions.

Challenges with the self-consistent implementation of closure models for anomalous electron transport in fluid simulations of Hall thrusters

The performance of closure models for the anomalous electron transport when self-consistently implemented in a fluid model for a Hall effect thruster is investigated. This cross-field transport, which is orders of magnitude higher than classical collisional transport, is represented as an effective collision frequency. The proposed closure models relate this transport coefficient to local fluid properties of the plasma. Before implementation, the models are calibrated against values of the collision frequency inferred empirically from a 9 kW Hall thruster at 300 V and 15 A. It is found that even though closure models match the empirical collision frequency values, they diverge from these values when implemented self-consistently in a Hall thruster code. Possible drivers of this behavior are examined, including the role of non-linearity in the governing equations of the Hall thruster fluid model, artifacts from using time-averaged calibration data, and the non-uniqueness of the empirically-inferred collision frequencies. These results are discussed in the context of their implications for discovering and validating new closures necessary for enabling fully-predictive Hall thruster models.

Discrete event simulation of vessel stationkeeping operations in ice-rich waters

This paper describes a high-fidelity numerical model that simulates vessel stationkeeping operations in ice-rich waters. The discrete event simulation engine incorporates several novel features, including new ice floe failure models for bow and midships locations; an ice floe creation strategy that facilitates rafting of ice floes; and a vessel thruster model that takes into account physical limitations such as thruster angle slew rates and propeller ramp rates. It accommodates a wide range of ice field specifications and runs in real-time on a standard desktop personal computer (Intel® Core™ i7 Processor or equivalent). The model has been validated using physical measurements of a generic drillship model in several broken ice conditions; it predicted thruster forces and motions that were comparable to those observed during dynamic positioning operations.