Thruster Performance Research Articles

Thrust measurements of a waveguide electron cyclotron resonance thruster

Direct thrust measurements are performed on a circular waveguide electron cyclotron resonance (ECR) thruster working at 5.8 GHz using a pendulum thrust balance with mechanically amplified displacement. Thrust levels between 1 and 3.5 mN are found for power levels in the range of 60–350 W and xenon flow rate between 2 and 8 SCCM. A maximum thrust efficiency of 3.5% is reached at 2 SCCM and 60 W. Plasma plume diagnostics are used to estimate the thruster partial efficiencies to understand the main losses, and to perform a comparative analysis between directly and indirectly measured thrust. Results suggest that the low energy conversion efficiency and propellant utilization efficiency (<6.4% and < 53%, respectively) are the key factors spoiling the ECR thruster performance. Finally, retarding potential analyzer measurements show the presence of energetic electrons with energy tail up to about 300 eV.

An Experimental Study of the Effects of Asymmetric Pitching Motion on the Hydrodynamic Propulsion of a Flapping Fin

Aquatic organisms have evolved exceptional propulsion and even transoceanic migrating capabilities, surpassing artificial vessels significantly in maneuverability and efficiency. Understanding the hydrodynamic mechanisms of aquatic organisms is crucial for developing advanced biomimetic underwater propulsion vehicles. Underwater tetrapods such as sea turtles use fins or flippers for propulsion, which exhibit three rotational degrees of freedom, including flapping, sweeping, and pitching motions. Unlike previous studies that often simplify motion kinematics, this study employs a specially designed experimental device to mimic sea turtle fins’ motion and explore the impact of pitching amplitude, asymmetric pitching kinematics, and pausing time on lift and thrust generation. Force transducers and particle image velocimetry techniques are used to examine the hydrodynamic forces and flow field, respectively. It is found that boosting the fin’s pitching amplitude enhances both its lift and thrust efficiency to a certain extent, with a more pronounced effect on thrust performance. Surprisingly, the asymmetrical nature of the pitching angle’s pausing time within one flapping cycle significantly influences the lift and thrust characteristics during sea turtle swimming; extending the pausing time during the forward and upward flapping process improves lift efficiency; and prolonging the pausing time during the downward flapping process enhances thrust efficiency. Furthermore, the mechanism for high lift and thrust efficiency is revealed by examining the vortices shed from the fin during different motion kinematics. This research contributes to a more comprehensive understanding of the fin’s hydrodynamic characteristic, providing insights that can guide the design of more efficient biomimetic underwater propulsion systems.

A review of the impact of ground test-related facility effects on gridded ion thruster operation and performance

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.

Mini Gaz Türbini (MGT) Motorunda Aspir Metil Ester-Jet A1 Karışımlarının Kullanımının Performans ve Emisyonlara Etkisinin Araştırılması

This study focused on the investigation of the effect of the SME-Jet A1 mixture on the thrust performance, fuel consumption and pollutant emissions of a small-scale jet engine, also the alternative of safflower methyl ester (SME) to Jet A1 fuel. The experiments were carried out by using bio jet fuels obtained by mixing Jet A1 and the fuel produced from safflower oil in taxi, approach, climb and take-off power cycles of a jet engine. The thrust forces of both types of fuel obtained from the percentage power values of the aircraft under real operating conditions were determined and accordingly CO, HC, CO2 emissions, fuel consumption and exhaust gas temperature measurements were made. As a result of the measurements, approximately 27.5% reduction in thrust was observed with the use of biojet. In addition, HC emissions decreased by up to 51%, while CO emissions increased by 30% at take off while being closer to each other at low rpm. While the CO2 emissions of methyl ester increased by 8-16% depending on the speed change, fuel consumption, while at an acceptable level at low rpm, exceeded 50% at take off.

A global model for evaluating discharge characteristics and performance of hollow cathodes

Hollow cathode, with the highest plasma density, current density, and temperature, becomes one of the most important components in the electro-thruster system. As the electric-propulsion thruster performance is directly related to the ionization rate, reliability, and lifetime of the hollow cathode, this paper develops a global model to study the effects of discharge current, gas flow rate, and gas species on the discharge characteristics in the insert and orifice regions of the hollow cathode. The emitter wall temperatures of hollow cathodes predicted by the global model are compared with experimental results from NSTAR thruster neutralization cathodes, confirming the model's validity. The influence of hollow cathode emitter material and structure sizes on the plasma parameters in the internal regions was also evaluated. The simulation results show that there is an optimal matching relationship between the discharge current and gas flow rate to guarantee the maximum ionization rate. The optimal working region for the hollow cathode has been determined under different energetic, regime and structural parameters. The global model established in this paper can quickly determine the key structure and operating parameters of hollow cathode at the design stage, and provide the theoretical basis for hollow cathode design and development.

Multi-objective aerodynamic optimization of expansion–deflection nozzle based on B-spline curves

An expansion–deflection nozzle (EDN) is an altitude-compensated nozzle that can accommodate a wide range of nozzle pressure ratio (NPR) variations. An EDN design with good thrust performance under both high- and low-NPR conditions can effectively improve the launch capability of the vehicle. In this study, a multi-objective aerodynamic optimization design is developed considering the performance of the EDN in both open and closed wake modes. The design method of the outer wall and pintle of the EDN is developed using B-spline curves. The design variables are the coordinates of the control points of the curves, and the objective functions are the thrust efficiencies of the EDN at NPRs of 30 and 400. The nozzle thrust is obtained using a Reynolds Averaged Navier–Stokes (RANS) equation solver and validated by experimental results. A radial basis function neural network and a non-dominated sorting genetic algorithm II (NSGA-II) are used to construct the surrogate model and search for the Pareto front, respectively. The relationship between the nozzle contour geometry and the nozzle thrust characteristics of the four optimised individuals on the Pareto front is discussed and analysed. The results demonstrate the effectiveness of the multi-objective optimization design for an EDN. One of the optimized designs improved the thrust efficiency at NPR = 30 by 3.5 % while improving the thrust efficiency at NPR = 400 by 0.6 %. Moreover, to ensure superior performance of the EDN in both operating modes, the nozzle length and pintle ending angle must be designed as a compromise, whereas a larger nozzle exit angle is favoured for both conditions. This study demonstrates the potential of the B-spline method for nozzle optimization design.

Research on the hydrodynamic performance of propellers under oblique flow conditions

The phenomenon of oblique water inflow is widespread in the operation of thrusters, which will cause adverse effects on the hydrodynamic performance of thrusters. In order to investigate the hydrodynamic performance and stress variation of the propeller in oblique flow, based on computational fluid dynamics theory, this paper takes the DTMB4119 propeller as the research object and conducts numerical simulation research on the propeller in oblique flow by solving the RANS equation. By calculating the open water performance curve and surface pressure distribution of the propeller, the rationality of the numerical method and the meshing are verified. Considering the flow field information such as velocity, oblique flow angles, flow line distribution, and pressure distribution, the changes in hydrodynamic characteristics of the propeller are simulated and analyzed. The results show that the uneven distribution of pressure on the propeller blade surface increases with a decrease in the advance coefficient. The force pulsation amplitude of a single blade increases with an increase in oblique flow angles. With the increase in oblique flow angles, the thrust, torque, and efficiency of the propeller show different increasing trends. With the increase in propeller advance coefficient, propeller thrust and torque decrease gradually, and propeller efficiency increases gradually. By using mature propellers, this paper has more reference value for studying the flow field around the ship hull and the hydrodynamic performance of propellers in the process of ship maneuvering.

Numerical and experimental research on the performance of an iodine-fed Hall thruster

The development of space technology brings about an increasing demand for electric thrusters. Iodine has been considered a feasible alternative to resource-critical xenon. Numerical and experimental methods are used to study the performance of the iodine-fed Hall thruster. The ionization and acceleration characteristics are investigated in the simulation with a particle-in-cell/Monte Carlo collision model. Different from previous simulations of noble gas, the dissociation equation of molecular iodine is added to the code for propulsive performance evaluation. A dissociation region in the discharge chamber is presented and described in detail. The propulsive performances of the iodine-fed Hall thruster are calculated by the plasma parameters. Meanwhile, the experimental measurements are finished for model verification and performance comparison at nominal conditions. The measured data is slightly lower than the simulated data. The error between them is about 1.65%. The reasons are analyzed and discussed. Then, the performance is predicted and measured using this simulated and experimental method within 20% mass flow rate and 10% anode voltage fluctuations relative to the nominal condition. Further optimizations of the simulation and experiment are in progress.

Experimental investigation on the performance of channel plasma thruster using tri-electrode DBD actuators under magnetic field

The performance parameters of a dielectric-barrier-discharge (DBD) plasma-driven channel flow thruster, including produced thrust, consumed power, and fluid mechanic effectiveness (defined as the thrust-to-power ratio), were characterized experimentally in this study. To improve the performance, a magnetic field was applied on the thruster with two different configurations: a two-electrode system and a tri-electrode system. Measurements showed that the produced thrust could increase by up to 32% and 56%, respectively, for the two-electrode and tri-electrode DBD thrusters under the applied magnetic field compared to those without magnets. Also, the consumed power corresponding to these states was reduced by approximately 32% and 19%, respectively. The effectiveness data profile exhibited a peak-shaped distribution, with its summit implying a saturation voltage that manifests a transition from the glow regime to the streamer regime. The effectiveness was decreased and increased, respectively, by exerting tri-electrode DBD actuation and using a magnetic field along with a thicker dielectric layer. The performance parameters were characterized by using power-law-based relationships with applied voltage, providing suitable interpretations to authenticate the measured data behavior. Finally, it was discussed that entropy maximization requires the effectiveness to have a summit-shaped distribution.

Numerical simulation and thrust performance optimization of water jet thruster

With the increasing use of water jet thrusters on ships, the demand for increasing their thrust performance and efficiency is also increasing. The impeller, as the core power component, is the key to the thrust of the water jet thruster. Therefore, to obtain a more energy-saving, low-carbon, and higher-thrust water jet thruster, this paper conducts an in-depth study on the impeller of the water jet thruster. The hexahedral grid is used to divide the internal flow field of the water jet thruster into structured grids, and the RANS equation and k-ε turbulence model are used to simulate the hydraulic performance of the original model, and then the blade of the impeller is optimized. Finally, compared with the original model, the simulation results of the optimization model show that the efficiency is increased by 4.8 %, and the thrust at the highest efficiency point is increased from 614 N to 1623 N. The optimized model greatly improves the efficiency and thrust of the water jet thruster, and the optimization effect is obvious.

Propelling plasma thrusters forward for spacecraft

Permanent magnets improve performance of magnet nozzle radiofrequency plasma thrusters while saving power.

Flow characteristics of ejector nozzles with different auxiliary intake valves

The ejector nozzle requires a third auxiliary airflow to improve its thrust performance at transonic speed. However, different auxiliary air intake structures will affect the third auxiliary flow, which in turn may change its thrust performance and internal flow field characteristics. Herein, we simulated four nozzles with different intake valve structures (sector angles of the open-close interval structure were 30°, 22.5°, 18°, and 15°, respectively) at transonic speed (Ma = 1.2). The results show that there is significant lateral flow inside the nozzle, which induces a multi-pair vortex. In addition, the nozzle with an open-close sector angle of 30° has the largest flow rate of 9.352 kg/s, which produces the largest thrust and the slowest dissipating flow vortex, but the distortion of the flow field in nozzles is the most obvious. However, with the reduction of the sector angle of the open-close intake valves (i.e., 22.5°, 18°, and 15°), the flow rate and the thrust of the nozzle decrease. Meanwhile, the dissipation of the flow vortex is accelerated, resulting in a weakening of the flow field distortion.

Exploration on the Possible Bump-on-Tail Instability in VASIMR

The bump-on-tail (BOT) instability is generally caused by a beam of energetic particles existing in relatively cold background plasma. The employment of second-stage wave-driven module in the variable specific impulse magnetoplasma rocket (VASIMR) yields the production of energetic ions, which could drive the BOT instability. The present work explores this possibility for the first time via numerical simulations based on the experimental data on the VASIMR, i.e., referring to VX-50. It is found that the BOT instability does exist even in the plume region away from antenna. The results indicate that velocity space diffusion provides a stabilizing effect on the nonlinear evolution of waves, while dissipation in the bulk plasma essentially impedes it. To show the practical values implied by these computations, the influences of this BOT instability on the power coupling and thrust are investigated particularly. These findings are valuable for VASIMR, as well as other plasma thrusters that yield energetic particles inside relatively cold background plasma, to suppress BOT instability and thus increase the power coupling efficiency and thrust performance.

Sequential Prediction of Hall Thruster Performance Using Echo State Network Models

Sequential Prediction of Hall Thruster Performance Using Echo State Network Models

Experimental investigation into efficiency loss in rotating magnetic field thrusters

An experimental investigation into the low thrust efficiency of a rotating magnetic field (RMF) thruster is presented. This technology is a low maturity but potentially enabling candidate for high-power in-space propulsion for use with alternative propellants. Direct thrust stand measurements of a 5 kW class RMF thruster were performed and show the thrust efficiency was 0.41 ± 0.04% with a specific impulse of 292 ± 11 s—typical values for RMF thruster operation. A suite of far-field probes were used to inform a phenomenological efficiency model for RMF thruster performance that accounted for divergence, power coupling, mass utilization, and plasma/acceleration efficiency. It was found that the plasma efficiency was the critically low term at 6.4 ± 1.0%. This indicates that the majority of the energy coupled to the plasma from the RMF antennas was lost before being converted to directed kinetic energy in the thruster beam. To determine the source of these losses, time-resolved measurements of the internal plasma properties were performed using a triple Langmuir probe. It was found that collisional excitation radiation and wall losses were the two dominant loss processes. This trend can be explained by the unusually high plasma density ( >1019 m−3) exhibited by this device compared to other electric propulsion architectures. Limitations in the probing techniques and strategies for improving RMF thruster performance are discussed given the results from the efficiency analysis.

Discharge characteristics of 100-W Hall thrusters under position matching between the anode and zero-magnetic-field region

Poor performance limits the wider application of 100-W-power class Hall thrusters. The effects of position matching between the anode and the zero-magnetic-field region (ZMFR) on the discharge process and performance improvement of 100-W Hall thrusters were investigated. The experimental results demonstrate that appropriately widening the ZMFR downstream of the anode improves the ion current and thrust, promotes plume focusing, and optimizes thruster performance. The thrust and anode efficiency is enlarged by 7.6 % and 20 % (relative value), respectively, when the ZMFR downstream of the anode is expanded by 0.2L (L is the channel length). The simulation results indicated that widening the ZMFR promoted the expansion of the high-ionization zone to the bottom of the channel, and increased the overall ionization rate. Moreover, as the ZMFR increases, the effective ion acceleration voltage increases. However, widening the ZMFR also aggravated the ion-wall interaction and reduced the propellant utilization rate. Therefore, the performance of the thrusters exhibited an optimal range as the length of the ZMFR increased. In addition, increasing the ZMFR did not affect the life of the thrusters.

Relationship Between Stance Width Variation During One Repetition Maximum Barbell Hip Thrust Performance and Kicking Speed for Young Elite Silat Athletes

Study purpose. This study aimed to determine the relationship between kicking speed performance and different stance widths during barbell hip thrust (BHT) at one repetition maximum (1RM) scores among young elite Silat athletes. Materials and methods. 15 male and 15 female Silat athletes with at least one year of resistance training experience and a mean age of 21.3 ± 1.2 years participated in this study. The load indicator performance associated with kicking performance was measured using 1RM load during BHT at varying stance widths. The data was analyzed using Pearson correlation tests through the SPSS Version 25 application. Results. A significant correlation was found between stance width, physical characteristics, and performance metrics with a low to moderate relationship. For physical features, weight (r=0.43, p<.05), height (r= 0.64, p<.05), and leg length (r= 0.44, p<.05) show positive relationship. Low to moderate significant relationships were found during WSW-RFK (r=0.39, p<.05) regarding 1RM and kicking performance. No significant correlations were found between NSW or NRW and the observed variables, except for a negative correlation between NRW and strength (r= -0.43, p < .05). There was a significant difference between males vs. females in RFK-NSW, RFK (p=0.006, p< .05), and LFK-NRW (p=0.001, p< .05) in kicking performance. Conclusions. This study revealed that stance width in barbell hip thrusts moderately correlates with physical characteristics and performance in young elite Silat athletes, where wider stances align with physical characteristics and narrower stances align with lower kicking performance. It also highlighted the importance of personalized training due to observed gender differences in kicking speed.

Design Methodology of Wind Turbine Rotor Models Based on Aerodynamic Thrust and Torque Equivalence

Limited by scaling effects, the physical model tests of FOWTs (floating offshore wind turbines) cannot simulate the aerodynamic loads on rotors correctly. To solve this problem, the real-time hybrid model tests in wind tunnels were developed and provided a feasible solution for the aerodynamic simulation. To perform the wind tunnel tests, the design of aerodynamic equivalent rotor models is most critical. In this study, an innovative methodology of aerodynamic equivalent design for the wind turbine rotors is developed based on GA (genetic algorithm). The NREL (National Renewable Energy Laboratory) 5 MW and DTU (Technical University of Denmark) 10 MW rotors are employed for the case studies to validate the proposed methodology. According to the results, the model-scale aerodynamic thrust performance can be accurately matched with the prototype in the entire region between cut-in and cut-out wind speeds, which allows the rotor model to provide correct thrust at different wind speeds. The variance of the aerodynamic torque with the wind speeds for the developed model is also in good agreement with the prototype, which could be beneficial for the design of the model-scale active pitch control strategy. Moreover, the applicability of the fitness functions of GA is discussed.

Promising methods for improving the radio-frequency ion thruster performance

Improving the reliability and efficiency of available electric propulsion schemes is one of the priority areas of space technology development. In particular, this should be done for ensuring the guaranteed removal of spacecraft to a disposal orbit at the end of their active life, which, in turn, will slow down the growth in the number of space debris objects in the most exploited regions of near-Earth space. The paper considers ways to improve the power and mass efficiency of one of the modern electric propulsion types - a radio-frequency ion thruster with an inductive radio-frequency discharge. Using an engineering physico-mathematical model, computational studies were performed to optimize the shape of the radio-frequency ion thruster main components, namely the discharge chamber and the grids of ion-extraction system. The thrust of the thruster was used as the optimization criterion; it was determined from the calculated ion density distributions in the radio-frequency discharge plasma. Such an approach to refine the performance improvement methods has not previously been applied to radio-frequency ion thruster. The ion density distributions, as well as the thruster integral characteristics determined from them, such as the thrust, total ion current from the thruster, propellant utilization factor, ionization cost and a number of others, were calculated for two actual standard sizes of radio-frequency ion thruster with the beam diameters of 80 mm and 160 mm, which can be used to solve the problems listed above. Besides, for the defined optimal configurations of thruster with two standard sizes the calculations were made to assess the possibility for increasing the thruster integral characteristics by applying an additional magnetostatic field in the radio-frequency discharge region. The study revealed the possibility of noticeable performance improvement compared to the basic radio-frequency ion thruster design with hemispherical discharge chamber and flat grids of the ion-extraction system.

Performance analysis of tilting pad thrust bearing incorporating the surface roughness, texture and turbulence effect

In order to improve the lubrication performance of the friction pair, the effect of composite micro-texture on the lubrication performance of the tilting pad thrust bearing is studied. Based on the structural model of tilting pad thrust bearing considering composite micro-texture, the lubrication characteristics of thrust bearing with composite micro-texture parameters and tilting pad parameters are analyzed. At the same time, the theoretical model of tilting pad composite micro-texture bearing considering roughness and turbulence effect is established, and the performance of thrust bearing considering roughness and turbulence effect is studied. The results show that the performance of composite micro-textured bearings is better than that of single micro-textured bearings, the performance of tilting pad bearings is better than that of parallel pad bearings, and the performance of circular composite fish-shaped micro-textured tilting pad bearings is the best. The optimal bearing fulcrum position is near the inner diameter, and the optimal fulcrum circumferential inclination angle is about 27.5°. Considering the roughness and turbulence effect, the maximum pressure and bearing capacity of the bearing improves, and the friction coefficient significantly reduces.