Static aeroelasticity of the propulsion system of ion propulsion unmanned aerial vehicles

“Ionic wind”generators are used as the main propulsion system in ion propulsion unmanned aerial vehicles(UAVs).Owing to the large size and poor stiffness of the electrode array in the propulsion system,the electrode array is prone to deformation under the flight load.In this work,the thrust characteristics and static aeroelastic properties of“ionic wind”propulsion systems were analyzed in detail.The simulation model for an“ionic wind”propulsion system was established by coupling a two-dimensional gas discharge model with a gas dynamics model.The influences of electrode voltage,spacing,size,and shape on the performance of the propulsion system were investigated.The fluid-solid interaction method was used to solve static aeroelastic characteristics under deformation.The aerodynamic and thrust performances of the elastic state and the rigid state were compared.It was found that the operating voltage,the distance between two electrodes,and the emitter radius had greater impacts on the thrust of the propulsion system.The propulsion system had a small contribution to the lift but a large contribution to the drag.In the elastic state,the lift coefficient accounted for 12.2%,and the drag coefficient accounted for 25.8%.Under the action of the downwash airflow from the wing,the propulsion system formed an upward moment around the center of mass,which contributed greatly to the pitching moment derivative of the whole aircraft.In the elastic state,the pitching moment derivative accounted for 29.7%.After elastic deformation,the thrust action point moved upward by 28.7 mm.Hence,the no lift pitching moment is reduced by 0.104 N$m,and the pitching moment coefficient is reduced by 0.014,causing a great impact on the longitudinal trimming of the whole aircraft.

Performance of a 4 cm iodine-fueled radio frequency ion thruster

The performance of an iodine radio ion thruster with a 4 cm diameter(IRIT4)was studied experimentally in this paper.Regulation of the mass flow rates of the iodine propellant is achieved by using a temperature control method of the iodine reservoir.Performance of the thruster using iodine as propellants is obtained at different total thruster powers of 40.6–128.8 W,different grid voltages of 1000–1800 V and the iodine flow rate of 100μgs^(-1).Results show that thrust and specific impulse increase approximately linearly with the increasing total thruster power and the screen grid voltage.The thrust of 2.32 mN and the specific impulse of 2361 s are obtained at the nominal total thruster power of 95.8 W and the screen grid voltage of 1800 V.It is also indicated that performance of the iodine propellant is comparable to that of the xenon propellant;and a difference between them is that the iodine thrust is slightly higher than xenon when the total thruster power is more than 62 W.At the nominal 95.8 W total thruster power,the thrust values of them are 2.32 m N and 2.15 mN respectively,and the thrust-to-power ratios of them are 24.2 mN kW^(-1)and 23.5 mN kW^(-1),respectively.

Factors Affecting Ion Thruster’s Performance

In this project,we investigated how ion thrusters produce propulsion and how the design of ion thrusters affects the performance of the thruster.In the experiment,we build a high voltage power supply(0-50 kV)and foil rings to produce ion wind.When considering the design of the thruster,we focus on three variables:the volume of the space,where ions are produced and the electric field intensity.Thus,to investigate the first variable we made foil rings with different radius and change the distance between the ring and positive cathode.To determine the propulsion produced we use a speed sensor to determine the magnitude of the wind produced.

Ion thruster accelerator grid erosion mechanism under extreme conditions of cylindrical erosion and chamfer erosion

In this paper,the abnormal experimental phenomenon on barrel erosion under extreme working conditions in the ultra-long life experiment(>10000 h)of ion thruster ion optics is studied by the Immersed-Finite-Element Particle-In-Cell Monte-Carlo-Collision(IFE-PIC-MCC)method and the grid erosion evaluation model.The transport process of beam ions and Charge Exchange(CEX)ions in the grid system,and the characteristics and mechanisms of the aperture barrel erosion under extreme erosion conditions(i.e.the cylindrical erosion and chamfer erosion)were systematically studied.Thanks to the advantage of the IFE method for dealing with complex boundaries in structured mesh,the aperture barrel erosion morphology of the accelerator grid is reconstructed accurately based on the experimental results.The results show that,with the evolution of working conditions,the mechanism of the aperture barrel erosion changes significantly,which relies heavily on the accelerator grid morphology.The change of the accelerator grid aperture barrel morphology has a significant effect on the behavior of CEX ions,and only affects the local electric field distribution,but has no effect on the upstream plasma sheath.As the erosion progresses,the erosion position moves downstream along the grid aperture axis direction,and the erosion range becomes narrower.Regardless of the erosion phase,the erosion rate of the CEX ions located downstream of the decelerator grid is the largest.The erosion rate is related to the mean incident energy and angle,and their variation is closely related to the position and trajectory of CEXions.

First thrust measurements in ionic multi-propeller rotational engines

Rotary ionic engines(RIEs)with multi-coaxial contra-rotating propellers(12.6 cm diameter)and their axial thrust are investigated in laboratory conditions,in air at atmospheric pressure,for the first time.The goal is to evaluate more advantageous configurations that may be scaled up and further help with development of rotary ionic drones.The propellers are designed with regular pin-emitter electrodes placed coaxially inside a cylindrical collector electrode.When high voltage is applied,propellers spin generating conventional axial thrust which is measured with an electronic scale in a“see-saw”setup.Up to 40 mN thrust was obtained in single propeller RIE at 2600 rpm,0.34 mA,37.5 kV,and an optimal collector electrode diameter of 17 cm.More thrust can be obtained with two and three propellers at constant current per propeller but at a decreased efficiency.Varying the axial propeller-separation showed that propeller-interaction is minimal above 5 cm.Thrust-to-power and thrust-tocurrent ratios were calculated and compared.We experimentally confirm here for the first time that within certain limits,the thrust-to-power variation can be assessed by the propeller kinetic energy-to-power ratio and also by the impedance of the gap(voltage-to-current ratio).A comparison of RIE arrays performance with one,two,and three coaxial propellers and the same total number of propellers per array(six)is also performed.RIE arrays with multi-coaxial propellers can provide larger thrust densities than single-propeller arrays.Also,arrays employing two coaxial propeller unit may be more weight effective.

Numerical Simulation of Characteristics of CEX Ions in Ion Thruster Optical System

Charge exchange （CEX） ions could inflict severe damages on the ion thruster optical system. This article is aimed at investigating the characteristics of the CEX ions and their influences upon the optical system by means of particle-incell（PIC） ion simulation and Monte Carlo collision（MCC） methods. The results from numerical simulation indicate that despite the fact that CEX ions appear in the entire beamlet region near the ion optical system, the ones that present themselves downstream of the accelerator grid have good reason for attracting more attention. As their trajectories are significantly affected by the local electric field, a great number of CEX ions are accelerated toward grids resulting in sputtering erosion. When the influences of the CEX ions are considered in the nulnerical simulation,there could hardly be observed augments in the screen grid current,but the accelerator grid current increases from zero to 1.4% of the beamlet current. It can be understood from the numerical simulation that the CEX ions formed in the region far downstream of the accelerator grid should be blamed for the erosion on the downstream surface of the accelerator grid.