Consolidation of milli-Newton FEEP Thruster Technology based on Porous Tungsten Multiemitters

Recently, a highly integrated electric propulsion system for ultra-precise generation of thrust on spacecraft has been developed using a porous matrix through which liquid indium flows during operation. In an effort to further improve the performance of this so-called porous tungsten crown emitter by activating all available sites for ion emission, the process of rapidly manufacturing the emitters via micro powder injection moulding has been revisited and modified. Three variations of the material composition and manufacturing processes have been performed in order to study the influence of the pore size on the ratio of active emission sites. Variations include a change in tungsten grain size as well as changes to the sintering atmosphere. Results indicate that only the densest variation, using the smallest grain size is viable for a thruster with high specific impulse. The obtained peak thrust during testing exceeded 1 mN. Despite the large peak thrust, the multiemitters maintain sub-µN capability.