Heating and plasma properties in a coaxial gasdynamic pulsed plasma thruster

Multiple experimental diagnostics are used to characterize a coaxial pulsed plasma thruster (PPT-4). Operating at a capacitor-stored energy E-0 of 9 J, thermocouple data indicate that half of the energy that reaches the PPT is lost as heat to the walls. Thrust-stand measurements yield an impulse bit of 29 +/- 2 muN (.) s/J, corresponding to an I-sp of 745 +/- 45 s and a thruster efficiency of 10.6 +/- 1.3 %. Quadruple electrostatic probe measurements indicate a symmetric plume with a peak electron density of 4.2 +/- 1.0 x 10(13) cm(-3) and an initial electron temperature of 2.0 +/- 0.3 eV. The ion Mach number u(i)/c(m) is generally supersonic with a value of 3.0 +/- 0.5. When the arrival time of peak n(e) is measured, an ion velocity of 34 km/s is indicated. A magnetic probe survey was used to measure magnetic field strength and identify enclosed current contours.