This paper proposes an application of microwave-sustained miniature plasmas to an ultra small thruster for next-generation microspacecraft and presents some results of numerical investigations of its thrust performance and preliminary experiments of Ar plasma discharges. Numerical results show that the thruster has enough thrust performance for a station-keeping maneuver of microspacecraft below the power of 10 W. Optical emission spectrometry implies a mode change in the plasma discharges inside the quartz tube 1.5 mm in inner diameter using 4-GHz microwaves at powers between 6 W and 10 W. (c) 2005 Elsevier B.V. All rights reserved.