A summary of performance and lifetime characteristics of pulsed and steady-state magnetoplasmadynamic (MPD) thrusters is presented. The technical focus is on cargo vehicle propulsion for exploration-class missions to the moon and Mars. Relatively high MPD thruster efficiencies of 0.43 and 0.69 have been reported at about 5000-s specific impulse using hydrogen and lithium, respectively. Efficiencies of 0.10 to 0.35 in the 1000-to 4500-s specific impulse range have been obtained with other propellants (e.g., Ar, NHa, NI). Electrode power losses of less than 20% at megawatt power levels using pulsed thrusters indicate the potential of high MPD thruster performance. Extended tests of pulsed and steady-state MPD thrusters yield total impulses at least two to three orders of magnitude below that necessary for cargo vehicle propulsion. Performance tests and diagnostics for life-limiting mechanisms of megawatt-class thrusters will require high-fidelity test stands, which handle in excess of 10 kA, and a vacuum facility whose operational pressure is less than 4 x 10 ~2 Pa. Nomenclature e = electronic charge, 1.6 x 10 ~1 9 C g = gravity acceleration, 9.81 m/s 2 H 0 = unheated propellant enthalpy, J/kg A P -specific impulses, s J = arc current, A (J 2 /m) c = onset parameter, A 2 -s/kg k = Boltzman's constant, 1.38 x 10~2 3 J/K m = mass flow rate, kg/s P = input power, W P a = power loss to anode, W P e = input electric power, W P L = power to water cooling system, W T = thrust, N T e = electron temperature, K V a = anode voltage drop, V AK = velocity increment required for a mission, m/s v = average exhaust velocity, m/s v\ = thrust efficiency f/ th = (P -P L )/P, thermal efficiency (j > = work function of anode material, V
