Investigation of heaterless hollow cathode breakdown

The development of long life high powered (>50A) hollow cathodes is of importance to meet the demand of increasingly powerful Gridded Ion engines and Hall Effect thrusters. High power cathodes typically operate at greater temperature ranges, which poses a significant challenge to maintain heater reliability. The heater component commonly used to raise the insert to emissive temperatures, has inherent reliability issues from thermal fatigue caused by thermal cycling with large temperature variations. A self-heating hollow cathode allows for potentially higher reliability through design simplicity of removing the heater component, and in addition there can be savings in mass, volume, ignition time and power. This study characterizes the initiation of the start-up process for a heaterless hollow cathode. As such the study analyses conditions of the initiation as a function of detailed geometrical and physical parameters. The Paschen curve can be seen to give a qualitative explanation for the breakdown voltage variance. The quantitative variations between the empirical results and Paschen curve are discussed in relation to non-uniform pressure simulations

Experimental progress towards the MicroThrust MEMS electrospray electric propulsion system

This paper describes the experimental progress towards an operational microfabricated electrospray thruster, as part of the EU FP7 “MicroThrust” Project. Microfabrication of an electrospray multiplexed thruster allows the seamless manufacturing of arrays of emitters, combining high specific impulse with sizeable thrust. The resulting thruster can thus be extremely efficient with a thrust approaching ≈100µN, depending on array size. We are working within the European FP7 project MicroThrust consortium to develop the complete MEMS electrospray array thruster for 10-100 kg class satellites to enable these small spacecraft to perform large delta-V missions (5 km/s). This includes the manufacture of MEMS Silicon electrospray emitters, and also a passive propellant feeding system, a miniaturized high voltage power supply, and the investigation of possible missions. We report here on the experimental testing of the micromachined Silicon capillary arrays, constituting arrays of either 91 or 127 emitters. A detailed description of the manufacture of the arrays will be described in a separate companion paper. To increase the specific impulse and thrust, and to reduce the plume angle, an accelerator has been integrated into the thruster Silicon chips. The thrust, and specific impulse has been measured using a Time-of- Flight (ToF) system, whilst the emitter current has been measured as the applied voltage was varied. The plume angle has been discerned using a translating Faraday cup

Characterisation of a thermionic plasma source apparatus for high density gaseous plasma antenna applications

none8noneAlexander Daykin-Iliopoulos, Franco Bosi, Fabio Coccaro, Mirko Magarotto, Athanasios Papadimopoulos, Paola De Carlo, Cristian Dobranszki, Igor Golosnoy and Steve GabrielDaykin-Iliopoulos, Alexander; Bosi, FRANCO JAVIER; Coccaro, Fabio; Magarotto, Mirko; Papadimopoulos, Athanasios; DE CARLO, Paola; Dobranszki, Cristian; Golosnoy and Steve Gabriel, Igo

Antimagicness of Generalized Corona and Snowflake Graphs

This paper provides constructions of antimagic labelings of two families of graphs, namely, sequential generalized corona graphs and generalized snowflake graphs. The labelings can also be used for some families of antimagic trees which are special cases of these families. Future lines of research for antimagic graph labelings are proposed