Thrust Gain Research Articles

Theory of the plasma thruster based on the rotating electromagnetic field

A theory of electrodeless electric propulsion systems (EEPS) based on the use of the solenoid magnetic field and the rotating electromagnetic field produced by antennas is developed, which includes a study of the plasma acceleration by the Radio Frequency (RF) field and the concomitant thrust. It was assumed that the frequency of the RF field exceeds the lower hybrid frequency but is much less than the electron gyrofrequency. Relations for the thrust are obtained and analyzed. It is shown that thrust gain is significant only when the RF-induced drift velocity well exceeds the fluid velocity of the injected plasma. It is revealed that the curvature of the magnetic field lines and the plasma acceleration in the region outside the solenoid are the factors which can considerably increase the thrust. On the other hand, it is found that the axial inhomogeneity of the plasma and some other factors are unfavorable for the thrust. The obtained results can be used for the optimization of particular experiments aimed to create a new thruster for long-time space missions.

Magnetohydrodynamic Analysis of Thrust Characteristics on Magneto-Plasma Sail with Plasma Magnetic Field Inflation by Low-Beta Plasma

Magneto-Plasma Sail (MPS) is a sail space propulsion system utilizing an artificial magnetosphere, which captures the solar wind dynamic pressure for the thrust production. The artificial magnetosphere is generated by on-board superconducting coils, and a significant feature of the MPS spacecraft is the deployment of the magnetic field inflation, in which the small magnetosphere by the on-board coils is inflated by the static pressure of the low-speed plasma injected from the spacecraft. In this study, a parametric survey is conducted using the axis-symmetric two-dimensional magnetohydrodynamic (MHD) simulation to investigate the relation between the thrust characteristics and the released plasma parameters (mass flow rate and the thermal beta value at the releasing point). As a result, it is indicated that the maximum value of the thrust gain, which is defined as the ratio of the MPS spacecraft thrust force to the Magnetic Sail thrust force, is 3.77 when the thermal beta value is 25 and mass flow rate is 100 in the non-dimensional parameter (when the magnetospheric size is assumed as about 300 km, the thrust force is 60 N and the mass flow rate is 3.6 mg/s). In addition, the thrust gain and the specific impulse tend to be higher as the mass flow rate is lower and the thermal beta value is higher.

Thrust Measurement of Magnetoplasma Sail in Laboratory Experiment

Magnetoplasma Sail (MPS) is one of the next generation in-space propulsion systems that utilize the interaction between the solar wind and the magnetosphere by way of an artificial magnetic field. In order to evaluate the thrust characteristics of MPS with plasma injection, the thrust measurement of a scale-model MPS (10-100 N class) was conducted in the laboratory using a pendulum-type thrust stand. The thrust was observed to increase by plasma injection, from 0.09 N to 0.17 N. The ratio between the thrust with plasma injection and the thrust without plasma injection was 1.9 (maximum thrust gain). The thrust of MPS was observed to increase with increasing the β value at the plasma injection point, and to our knowledge, this study is the first to experimentally achieve this result.

Analysis of Small-scale Magneto Plasma Sail and Propulsive Characteristics

(Received June 10th, 2013) Magneto Plasma Sail (MPS) is spacecraft propulsion that produces an artificial magnetosphere to block solar wind particles, and thus impart momentum to accelerate a spacecraft. In the present study, we conducted three-dimensional particle-in-cell simulations on small-scale magnetospheres (< i on Larmor radius, 100 km) to investigate thrust characteristics of MPS, in which the magnetosphere is inflated by an additional plas ma injection. As a result, we revealed that the finite thrust generation and the increase in thrust are obtained on the small-scale magnetosphere even if the electron kinetics is taken into consideration. The thrust of MPS (1.0 mN) becomes up to 14 times larger than that of the original magnetic sail (0.07 mN). However, it was also revealed that the thrust gain of MPS defi ned as thrust of MPS / (thrust of magnetic sail + thrust of plasm a jet) is approximately unity and thrust-mass ratio and thrust-power ratio are further smaller compared with other existing propulsion system. An extensive improvement of a thrust is required for the realization of MPS.

Two-Dimensional Particle-In-Cell Simulation of Magnetic Sails

A magnetic sail is spacecraft propulsion that produces an artificial magnetosphere to block solar wind particles and thus impart momentum to accelerate a spacecraft. In the present study, the authors conducted two-dimensional particle-in-cell simulations on small-scale magnetospheres to investigate thrust characteristics of a magnetic sail and its derivative, magnetoplasma sail, in which the magnetosphere is inflated by an additional plasma injection. As a result, the authors found that the electron Larmor motion and the charge separation become significant on such a small-scale magnetosphere and the thrust of the magnetic sail is affected by the cross-sectional size of the charge-separated magnetosphere. The authors also reveal that the plasma injection, on the condition that the kinetic energy of plasma is smaller than the local magnetic field energy (), can significantly inflate the magnetosphere by inducing diamagnetic current in the same direction as the onboard coil current. As a result, the magnetoplasma sail thrust is increased effectively by an additional plasma injection: the magnetoplasma sail thrust () becomes up to 7.5 times larger than the original thrust of the magnetic sail (). In addition, they found that the thrust gain of the magnetoplasma sail, defined as “magnetoplasma sail thrust/(magnetic sail injection thrust)” becomes up to 2.2.

Insight in the Performance of Scramjet Combustor Based on Orthogonal Experimental Design

A numerical insight was accomplished to optimize the scramjet combustor configuration based on orthogonal experimental design. Parametric modeling of combustor configurations was performed by the orthogonal array with 13 factors at 3 levels. Numerical simulations were proceeded by k-ε standard turbulence model and eddy-dissipation model in the combustion process. The performance indexes of combustion efficiency, total pressure recovery coefficient and thrust gain coefficient were evaluated. Detailed comparison with the effect of the factors on the performance was also carried out to demonstrate the main factors and determine the optimal configuration. The analysis of the extreme differences of the factors indicates that the main factors affecting combustion efficiency were the length of the wedge, the length depth ratio of the cavity, the depth of the cavity, and the length of the expanding section; The main factors affecting total pressure recovery coefficient are the angle of the primary combustor, the length of the expanding section, and the thickness of the strut; The main factors affecting thrust gain coefficient are the thickness of the strut, the length of the expanding section, and the angle of the secondary combustor. Validation of the optimal configuration is then confirmed that its performance is higher than the rest of the configurations, with the combustion efficiency of 0.915 and the total pressure recovery coefficient of 0.486, which are 31.5% and 65.9% higher than the experimental results, respectively.

On plasma detachment in propulsive magnetic nozzles

Three detachment mechanisms proposed in the literature (via resistivity, via electron inertia, and via induced magnetic field) are analyzed with an axisymmetric model of the expansion of a small-beta, weakly collisional, near-sonic plasma in a diverging magnetic nozzle. The model assumes cold, partially magnetized ions and hot, isothermal, fully magnetized electrons. Different conditions of the plasma beam at the nozzle throat are considered. A central feature is that a positive thrust gain in the nozzle of a plasma thruster is intimately related to the azimuthal current in the plasma being diamagnetic. Then, and contrary to existing expectations, the three aforementioned detachment mechanisms are divergent, that is, the plasma beam diverges outwards of the guide nozzle, further hindering its axial expansion and the thrust efficiency. The rate of divergent detachment is quantified for the small-parameter range of the three mechanisms. Alternative mechanisms for a convergent detachment of the plasma beam are suggested.

Experimental and Numerical Studies on Lobed Ejector Exhaust System for Micro Turbojet Engine

:For the purpose of improving thrust and cooling the wall of the nozzle on a micro turbojet engine, the aerodynamic characteristics micro lobed ejector, which consists of a lobed nozzle and mixing, is studied using numerical calculations and experiments. Firstly, the aerodynamic performances of several lobed nozzle jectors with different geometries were calculated based on the Reynolds-averaged Navier-Stokes equations with k -ε turbulence model. The numerical results show that the pumping ratio is enhanced with the increase of lobe expansion angle in the range of 5 to 17 degrees. Firstly, the thrust gain increases and then decreases with the increase of lobe expansion angle. Secondly, taking into account of the aerodynamic performances and weight penalty, the thrust and the wall temperature of the nozzle of a micro turbojet engine with a lobed ejector of 5-degree expansion angle was measured. Experimental data demonstrate that the lobed ejector increases the thrust of the engine by 2.99% relative to the convergent nozzle. Moreover, the peak temperature of nozzle wall is decreased by 30%. At the same time, the pumping air mixed with the exhaust plume decreases the temperature of the plume. It is believed that the lobed ejector has another advantage of reducing the infrared radiation of the micro turbojet engine.

Unsteady aerodynamics of two interacting yacht sails in two-dimensional potential flow

In this paper, unsteady thin aerofoil theory is extended to the case of two interacting aerofoils that oscillate harmonically perpendicular to the direction of the incident flow. The two aerofoils represent the headsail and mainsail of a yacht that sails upwind in waves. The developed theory is validated against theoretical data from the literature and results from wind tunnel tests with rigid, high-aspect ratio sail models oscillating at reduced frequencies fromk= 0 tok= 0.68. Good agreement is found between the predicted and measured chordwise pressure distributions. An application of the theory to the case of an International America's Cup Class yacht reveals that the time-varying components of the aerodynamic forces are small and that the thrust gain is minimal, i.e. only very little energy can be extracted from the unsteady flow about the sails. No attempt is made to investigate the influence of the flexibility of the sails, three-dimensional effects or phenomena related to dynamic stall.

Mixing enhancement via nozzle trailing edge modifications in a high speed rectangular jet

An aspect ratio 3 rectangular nozzle with design Mach number 2 was used to investigate the effects of trailing edge modifications on mixing enhancement and to explore the sources of streamwise vorticity at the fully expanded jet Mach numbers 1.75, 2.0, and 2.5. The trailing edge modifications are simple cut-outs in the plane of the nozzle at the nozzle exit. The investigation of mixing and interaction between mixing layers and vortices was performed by the laser sheet illumination technique. Through surface flow visualizations and wall pressure measurements, the investigation of the major source of streamwise vorticity was carried out. In addition, the variation of thrust generated by the nozzle with modified trailing edges was investigated. In the underexpanded flow condition, the major source of streamwise vorticity was determined to be the spanwise surface pressure gradient on the modification. Substantial mixing enhancement was achieved in this flow regime. On the other hand, in the overexpanded flow regime, the role of streamwise vortices in mixing and the source of streamwise vorticity were unclear, and mixing enhancement was not substantial. No measurable thrust loss or gain was obtained for nozzles with trailing edge modifications, regardless of the type of modification.

A Experimental Study Concerning Mutual Interference between Propeller and Rudder

This report pertains to the experimental results obtained relative to the reciprocal interference resulting from the combination of the Troost B.4-40 type or other propellers, and the reaction rudder as described in the theoretical report which was read in the spring meeting in 1961.A comparison of the present experimental results with the theoretical conclusion reached in the said report has clarified the following matters : (1) It is supporsed that the propeller is affected by tne rudder largely due to the potential wake-of the rudder and its lifting line, while the deformation of the propeller free vortices under the influence of the rudder, on the other hand, does not practically affect the performance of the propeller.(2) Of the influences by the propeller exerted on the rudder, nonstationary effect is most serious. In case the pitch ratio of the propeller is minor, the effect is so large that it nearly overwhelms any thrust gain due to the rotatory flow of the propeller. Accordingly, the theoretically calculated thrust gain does not necessarily conform to the experimental value in quantitative way, but, in regard to the comparative superiority or inferiority of each of the rudders, the theoretical and experimental results coincide with each other.(3) The pitch distribution of the propeller to be combined with the reaction rudder should preferably be the decreasing distribution (with increased pitch at the blade root), which was suggested by the theoretical study.