Model of particulate interaction with plasma in a Teflon pulsed plasma thruster

The presence of particulates [referred to as macroparticles (MPs)] in the p lume of a pulsed plasma thruster (PPT) may affect interaction with the spac ecraft. Possible particulate related effects depend on particulate properti es. The MPs emitted into the plasma during the discharge may be charged, ac celerated, and heated by the ion, electron, and neutral fluxes depending on the MP residual time, Different aspects of MP-plasma interaction in the ex perimentally observed range of MP radii (0.1-100 mum) are analyzed. It is f ound that the charging time is smaller whereas the steady-state potential i s larger in the case of a large MP. A 1-mum MP is found to have a charge of about 10(5) electrons in the case of an electron density of about 10(23) m (-3). The two primary forces acting on the MP in the PPT discharge are a dr ag force due to collision with neutral atoms and ions and an electric force due to the presence of the electric field in the current carrying plasma. The calculation of the MP velocity shows that the maximum possible velocity of a 1-mum MP is about 230 m/s, which is close to that estimated experimen tally. Only small MPs (similar to0.1 mum) can be entrained by the plasma je t, whereas large MPs are generally slower and how substantially behind the plasma jet. MP temperature and decomposition rates are calculated by solvin g a heat balance equation. It is found that small MPs (<1 <mu>m) may comple tely decompose during a 1-mus pulse.