Micropropulsion for small spacecraft: a new challenge for field effect electric propulsion and microstructured liquid metal ion sources

The growing interest in the use of microspacecraft is driving a critical need for new micropropulsion systems. The constraints on mass, dimension and power with which microspacecraft have to contend pose severe challenges to the system design. This general definition allows the inclusion of a wide range of concepts, from scaled-down versions of existing thrusters operating at reduced power levels to completely redesigned microelectromechanical-fabricated thrusters with micron characteristic sizes. More than ten years ago, microelectromechanical-based propulsion was first introduced in the form of a proposed microfabricated field effect electric propulsion (FEEP) liquid metal ion thruster concept. Now a review will be given on basic features of liquid metal field emission sources, on selection criteria for liquid metal propellants for FEEP thrusters, on the principles of microstructured liquid metal ion sources (MILMIS) and finally on the miniaturization of MILMIS. Copyright (C) 2004 John Wiley Sons, Ltd.