  Conventional snowplow/1-D models assume the existence of single completely
ionized plasma sheet in the discharge chamber of pulsed plasma thrusters
(PPTs). However, extensive experimental analysis and observations suggest the
presence of multiple plasma streams and partial ionization of the propellant
gas. A multi-layered plasma-neutral mass sheet one-dimensional numerical model
is developed for PPTs in the present paper. The model accounts for the
secondary plasma sheets generated due to the crowbar breakdowns as well as the
neutral gas generated after the main discharge. The model accurately calculates
the position of the plasma and neutral mass sheets, mean exit velocity, thrust
delivered and the mass of individual plasma sheet developed in PPTs. The model
is validated and discussed for two different ablative pulsed plasma thrusters.
In the last section, the plasma sheet model and electrical circuit model are
also validated for a liquid propellant PPT developed at the University of
Tokyo. Results show that the multi-sheet assumption provides an accurate
prediction for the discharge current and performance parameters. The multiple
sheet assumption model accounts for most of the experimentally observed
phenomena's which the conventional slug models tend to ignore.
