Experimental Performance of Field Emission Microthrusters

This paper presents the results of a series of tests performed on a set of field emission electric propulsion (FEEP) emitters, including recording of the current/voltage characteristic curves and ion beam scanning with electrostatic probes. This work was aimed at collecting reliable, systematic thruster performance data to be used as a basis for the definition of a reference thruster mathematical model. Four FEEP emitters with three different slit height values were tested. The thrust produced covered the 1-170-micro-N range. Repeatability of thruster performance was found to depend on the degree of wetting of the emitter slit and on the presence of glow discharge between the electrodes. The latter represented an undesired effect and was therefore eliminated after the first series of experiments. Wetting, on the other hand, proved to be of the utmost importance. In some cases, thruster performance improved by as much as 150 percent within a few days of the beginning of the test, as a result of enhanced slit wetting. (Author)