Quasi-Steady Magnetoplasmadynamic Thruster Performance Database ∗ E.Y. Choueiri † and J.K. Ziemer ‡ Electric Propulsion and Plasma Dynamics Laboratory (EPPDyL) MAE Dept. Princeton University Princeton, New Jersey 08544 § Nomenclature E Discharge energy I b Impulse bit I cgb Cold gas impulse bit I hb “Hot” impulse bit I sp Specific impulse J Thruster current m cb Cold gas mass bit m b Propellant mass bit ˙ m Mass flow rate m eff Effective mass of thruster-thrust arm assembly P Power T Instantaneous thrust u cge Cold gas exhaust velocity V Thruster voltage V m Voltage of mass pulse waveform at quasi-steady- state plateau x Position of thrust stand arm δV Voltage “hash” fluctuations Δt h Effective “hot” pulse duration Δt m Effective mass pulse duration Δ˙ x Change in velocity due to impulse η I Impulsive efficiency η T Thrust efficiency ζ eff Damping constant of thrust arm motion ω n,ef f Effective natural frequency of thruster-thrust arm assembly * Presented at the 34 th AIAA Joint Propulsion Conference, Cleveland, OH, July 13-16, 1998. AIAA-98-3472. † Chief Scientist at EPPDyL. Assistant Professor, Applied Physics Group, MAE Dept. and Associated Faculty at the Dept. of Astrophysical Sciences, Program in Plasma Physics. Senior Member AIAA. ‡ Graduate Student, Research Assistant. Presently at NASA-JPL. Member AIAA. § Research supported by NASA-JPL’s program on advanced propulsion. <a> Arithmetic average of quantity a over the quasi-steady plateau. Abstract The performance of a coaxial, gas-fed, self-field, quasi-steady pulsed magnetoplasmadynamic thruster (MPDT) was measured using a swinging gate thrust stand equipped with a laser interferometer and an RF proximity transducer. Careful calibration of the thrust stand, and other diagnostics insured that the measurement errors, barring the effects of fluctua- tions in the discharge voltage, are well below 2%. The measurements were carried out for various mass flow rates, ranging between .5 and 6 g/s and for four pro- pellant gases: argon, xenon, hydrogen and deuterium. The data set can be interpreted to describe both the performance of steady-state high-power (multi- megawatt) MPDTs and quasi-steady pulsed MPDTs that can operate at low spacecraft bus power. The re- sults were curve-fit and compiled into a performance database that is intended as a data source for sys- tem or mission analysis as well as for the validation of analytical and numerical models of the MPDT. 1 Introduction 1.1 Status of MPDT Technology Quasi-steady pulsed operation of self-field magne- toplasmadynamic thrusters (MPDTs) was originally intended[1, 2] as a means of simulating multi- megawatt steady-state thrusters in the laboratory. The need to operate at high instantaneous power stems from the early[3] recognition that MPDTs op- 1