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Iodine has proven to be a promising alternative to xenon as a propellant for Hall and ion thrusters. High atomic mass and favourable ionization characteristics, comparable to xenon in terms of propulsive performance, together with lower cost compared to xenon makes it an attractive option. However, its reactivity and corrosive nature raise concerns. Tests to assess material compatibility and determine whether thruster components are susceptible to corrosion are unavoidable for its safe adoption as a propellant. This paper describes the main results of an experimental campaign aimed at a qualitative assessment of the compatibility with iodine of different materials. The study included more than fifteen materials that find application in electric propulsion devices, such as cathodes, thrusters and feeding systems, including ceramics such as LaB 6 , polymers, iron and aluminum alloys, and graphite. The specimens were exposed to iodine vapor environments at temperatures reaching approximately 200 °C for extended periods (from three to over 30 h) or were directly exposed to liquid iodine. The experimental setup and results of morphological and elementary analyses are presented and discussed. The research provides some insights into the viability of using iodine as a propellant and the potential challenges associated with its corrosive properties. [ABSTRACT FROM AUTHOR]

Thermionic hollow cathodes are currently used as sources of electrons in a variety of space applications, in particular as cathodes/neutralizers of electric thrusters (Hall effect and ion thrusters). Numerical tools are needed to guide the design of new devices before their manufacturing and testing, since multiple geometrical parameters influence the cathode performance. A reduced-order, numerical model was developed to assess the performance of orificed hollow cathodes, with a focus on the operational lifetime. The importance of the lifetime prediction is tied to its impact on the operational lifetime of the thruster to which the cathode is coupled. The cathode architecture consists of a refractory metal tube with an internal electron emitter made of lanthanum hexaboride (LaB 6 ). The choice of LaB 6 accounts for the reduced evaporation rate, the low sensitivity to poisoning and the absence of an activation procedure with respect to oxide cathodes. A LaB 6 emitter is thus a valuable option for long-lasting cathodes, despite its relatively high work-function and reactivity with many refractory metals at high temperatures. The suggested reduced-order model self-consistently predicts the key parameters of the cathode operation, shedding light on the power deposition processes as well as on the main erosion mechanisms. Preliminary results showed good agreement with both the experimental data collected by Alta and data available from the literature for different operating conditions and power levels. Next developments will include further comparisons between theoretical and experimental data, considering cathodes of various size and operating conditions. [ABSTRACT FROM AUTHOR]