Bulletin of the American Physical Society
62nd Annual Gaseous Electronics Conference
Volume 54, Number 12
Tuesday–Friday, October 20–23, 2009; Saratoga Springs, New York
Session FT2: Plasma Thrusters |
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Chair: Ane Aanesland, CNRS - Ecole Polytechnique Room: Saratoga Hilton Ballroom 2 |
Tuesday, October 20, 2009 8:00AM - 8:15AM |
FT2.00001: Optical Measurement of a Microwave-excited Miniature Plasma Source for Micro Propulsion Yoshinori Takao, Takeshi Takahashi, Shunsuke Kitanishi, Koji Eriguchi, Kouich Ono Reducing the scale of propulsion systems is of critical importance for microspacecraft. This paper is concerned with an application of microplasmas to a microthruster. The microthruster consists of a cylindrical microplasma source 10 mm in length and 1.5 mm in inner diameter and a conical Laval micronozzle 1.0 mm in length with a throat diameter of 0.2 mm. The microplasma source produces hot Ar plasmas by $2-11$ GHz microwaves in the pressure range from 5 to 50 kPa at input powers below 6 W; and the micronozzle converts such high thermal energy into directional kinetic energy as a supersonic jet. The gas/rotational temperature and the plasma electron density were measured by adding a small amount of N$_{2}$ and H$_{2}$, respectively, and then fitting the experimental data to theoretical calculations. Plasma diagnostics showed that the electron density and rotational temperature obtained were $10^ {19} - 10^{20}$ m$^{-3}$ and $700 - 1000$ K, respectively, in the range of Ar gas flow rate from 10 to 70 sccm at input powers of 3 and 6 W. [Preview Abstract] |
Tuesday, October 20, 2009 8:15AM - 8:30AM |
FT2.00002: Particle-in-cell simulation for the acceleration channel of a Hall thruster Hae June Lee The Hall electric thruster is an electric propulsion device that allows a high specific impulse compared with chemical thrusters, and thus is very useful for a small satellite. A two-dimensional particle-in-cell simulation with Monte-Carlo Collision (MCC) has been developed to investigate the discharge in the acceleration channel of a stationary plasma thruster. The dynamics of electrons and ions under the magnetic field are calculated at the time scale of electrons. Xenon neutrals are injected from the hall in the anode and experience elastic, excitation, and ionization collisions with electrons and are scattered by ions. These collisions are simulated by using an MCC model. The neutral particle motion is coupled with the plasma dynamics in the simulation. Investigated are the effects of magnetic field profiles, gas pressure, electron current density, and the applied voltage. The simulation method for the external circuit equation is also discussed. [Preview Abstract] |
Tuesday, October 20, 2009 8:30AM - 8:45AM |
FT2.00003: Effects of the cathode electron emission on transient phenomena in magnetized thruster discharge Yevgeny Raitses, Jeffrey B. Parker, Nathaniel J. Fisch Large-amplitude, low-frequency, discharge current oscillations invariably occur in the Hall thruster discharge. This discharges are characterized by magnetized electrons and unmagnetized ions. The oscillations are thought to result from various ionization mechanisms [1]. A rotating potential perturbation, called a spoke, is observed to propagate in the E $\times $ B direction for certain magnetic field topologies of the thruster discharge, including both cylindrical and annular configurations [2, 3]. We show that increasing the cathode electron emission curiously suppresses both the rotating spoke and the low frequency oscillations. This effect correlates with a change in the local V-I characteristics of the plasma discharge. In particular, in the regime with the enhanced electron emission, there are no plasma regions with negative differential resistance, which are normally observed for the self-sustained operation of the thruster discharge. [1] S. Barral and E. Ahedo, Phys. Rev. E\textbf{ 79}, 046401 (2009). [2] G. S. Janes and R. S. Lowder, Phys. Fluids \textbf{9}, 1115 (1966). [3] Y. Raitses, A. Smirnov and N. J. Fisch, Phys. Plasmas \textbf{16}, 057106 (2009). [Preview Abstract] |
Tuesday, October 20, 2009 8:45AM - 9:00AM |
FT2.00004: Electrode Polarity Effects in Direct Current Glow Discharges for Supersonic Flow Control Shankar Mahadevan, Laxminarayan Raja Computational simulations of air glow discharge plasma in the presence of supersonic flow are presented. The glow discharge model is based on a self-consistent, multi-species, continuum description of the plasma. A finite-rate air chemistry model with 11 species is validated against experiments from the literature at p=600 mTorr. The validated air plasma model is then used to study the effect of the surface plasma on M=3 supersonic flow at freestream pressure 18 Torr and the corresponding effects of the flow on the discharge structure. The Navier-Stokes equations are solved on the entire computational domain, and the plasma equations are solved on a smaller subdomain consistent with the typical length-scale of the glow discharge. Results indicate that O$^{-}$ can have comparable concentrations to electrons in the pressure range 1-20 Torr. The peak gas temperature from the computations is found to be 1420 K with the surface plasma alone, and 1180 K in the presence of supersonic flow with the cathode located upstream with respect to the flow direction. The effect of placing the cathode downstream with respect to the flow direction is investigated. For the case studied in this work the primary effect of the plasma on the supersonic flow is volumetric heating. [Preview Abstract] |
Tuesday, October 20, 2009 9:00AM - 9:30AM |
FT2.00005: Microdischarge plasma thrusters for small satellite propulsion Invited Speaker: Small satellites weighing less than 100 kg are gaining importance in the defense and commercial satellite community owing to advantages of low costs to build and operate, simplicity of design, rapid integration and testing, formation flying, and multi-vehicle operations. The principal challenge in the design and development of small satellite subsystems is the severe mass, volume, and power constraints posed by the overall size of the satellite. The propulsion system in particular is hard to down scale and as such poses a major stumbling block for small satellite technology.\textbf{ }Microdischarge-based miniaturized plasma thrusters are potentially a novel solution to this problem. In its most basic form a microdischarge plasma thruster is a simple extension of a cold gas micronozzle propulsion device, where a direct or alternating current microdischarge is used to preheat the gas stream to improve to specific impulse of the device. We study a prototypical thruster device using a detailed, self-consistent coupled plasma and fluid flow computational model. The model describes the microdischarge power deposition, plasma dynamics, gas-phase chemical kinetics, coupling of the plasma phenomena with high-speed flow, and overall propulsion system performance. Unique computational challenges associated with microdischarge modeling in the presence of high-speed flows are addressed. Compared to a cold gas micronozzle, a significant increase in specific impulse (50 to 100 {\%}) is obtained from the power deposition in the diverging supersonic section of the thruster nozzle. The microdischarge remains mostly confined inside the micronozzle and operates in an abnormal glow discharge regime. Gas heating, primarily due to ion Joule heating, is found to have a strong influence on the overall discharge behavior. The study provides a validation of the concept as simple and effective approach to realizing a relatively high-specific impulse thruster device at small geometric scales. [Preview Abstract] |
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