Experiments conducted on solid-state ionic membranes that convert atoms into ions that can in turn be extracted into energetic beamlets and thereby produce thrust are described. The capability of ionizing and transporting ions is shown to be both rapid (over 10 mA/cm 2 ) and efficient (of order 1 eV/ion). Although similar in appearance to cesium contact sources, solid-state ionic membrane devices are shown to operate successfully at lower temperatures (400 to 700 °C) thus making them much more efficient than cesium- based devices. The process of extracting the ions by field emission is shown to limit the extracted ion current density. The need to select an emissive surface material/propellant ion combination with a low work function is suggested. Based on successful demonstrations of ion extraction, the Emissive Membrane Ion Thruster is proposed and shown to offer the potential for substantial reductions in ion thruster system cost and complexity as well as improvements in scalability and reliability compared to existing ion thruster designs