Performance Modeling of an RF Coaxial Plasma Thruster

Abstract

The RF plasma thruster has considerable potential to ease the impact of severe constraints on power, mass, volume and lifetime of microsatellite propulsion systems. This concept is classified as an electrothermal propulsion system and exploits RF capacitively coupled discharge (RFCCD) for heating of a propellant. The plasma is characterized as a low-power discharge possessing a low-current density with high uniformity and propagating through low-pressure gas. To assess computationally the thruster's propulsive capabilities as a function of mass flow rate, electrode separation, RF frequency and power input, a numerical model comprises particle-in-cell/Monte Carlo (PIC/MCC) and Direct Simulation Monte Carlo (DSMC) algorithms. Thruster performance is investigated by permuting electrode geometry (0.5 -2 cm), chamber pressure (0.05 -50 Torr), applied voltage (100 -500 V), and frequency (10 -1000 MHz). For this parameter space, PIC/MCC determines overall trends in plasma characteristics. One selected case (3 Torr, 500 V, 200 MHz) and its set of conditions (plasma density, plasma heating, gas temperature, etc.) form the basis for an in-depth flow field and thrust performance analysis with DSMC. Assuming adiabatic wall conditions, the RF plasma thruster achieves a specific impulse of 104.4 s with Argon at the throat Reynolds number of 25. The RF heating increases the specific impulse by 125 %. This study shows that propulsive capability of the RF plasma thruster can be enhanced by increasing the discharge chamber length, redesigning the nozzle contour, and using propellants with lower molecular weights.

2D Fluid Model for Axisymmetric RF Ion Thruster Cylindrical Discharge Chamber

“…Stein 4 gives an example of PIC/DSMC algorithms used for kinetic modeling of the plasma in the discharge chamber. Mistoco 5 performed one of the most recent works on the RF ion thruster modeling.…”

Experimental and Computational Investigation of a RF Plasma Micro-Thruster

“…These parameters will determine plasma formation and plasma characteristics, which will ultimately affect propellant heating and thruster lifetime. 6 The RFCCD thruster, shown schematically in Fig. l(A), is a prototype device similar to that described in Ref.…”

“…To assess the thruster's propulsive capabilities the RF plasma thruster can be modeled numerically utilizing Particle-In-Cell/Monte Carlo Collision (PIC/MCC) and direct simulation Monte Carlo (DSMC) algorithms. 6 .7 The PIC/MCC method is used to determine plasma characteristics within the coaxial discharge annulus. The argon collision model employed in the computations includes electron-neutral ionization, charge exchange, lumped excitation, and elastic electron-neutral and ion-neutral scattering.…”

Plasma-Neutral Heat Transfer in Coaxial RF Argon Discharges

“…Our previous work [21][22][23] investigated the effects of pressure and frequency on performance of a 50W RFCCD microthruster. This was done at a constant applied potential and inner radius corresponding to conditions similar to that in the experiments.…”