New materials and processes for field emission ion and electron emitters

Abstract

Indium field emission electric propulsion (FEEP) thrusters have been developed in the past as an enabling technology for ultraprecise formation flying applications such as on LISA Pathfinder. New missions require a large thrust range from μN into the mN range. A novel emitter type using micro-powder injection molding has been developed to produce porous tungsten crown emitters that promise very reliable and stable performance from sub-μN up to several hundred μN, as well as rapid manufacturing which had been a major issue in the past. Porous emitters were also investigated as electron emitters, which could enable bi-polar operation and therefore replace a separate neutralizer that is otherwise required. Recently, new materials such as rhenium and other manufacturing techniques including laser sintering were investigated to further explore the promising field of field emission technologies for space applications. This paper gives an overview on our recent porous emitter technology efforts and summarizes potential applications as well as terrestrial spin-off possibilities.