Development of Hollow Cathodes for Space Electric Propulsion at Sitael

Abstract

Hollow cathodes are electron sources used for the gas ionization and the beam neutralization in both ion and Hall effect thrusters (HETs). A reduction of power and propellant consumption from the cathode is particularly needed in small satellite applications, where power and mass budgets are inherently limited. Concurrently, the interest in high-power HETs is increasingly fostered for a number of space applications, including final positioning and station-keeping of Geostationary Earth Orbit (GEO) satellites, spacecraft transfers from Low Earth Orbit (LEO) to GEO, and deep-space exploration missions. As such, several hollow cathodes have been developed and tested at Sitael, each conceived for a specific power class of thrusters. A numerical model was used during the cathode design to define the geometry, in accordance with the thruster unit specifications in terms of discharge current, mass flow rate, and lifetime. Lanthanum hexaboride (LaB6) hollow cathodes were successfully developed for HETs with discharge power ranging from 100 W to 20 kW. Experimental campaigns were carried out in both stand-alone and coupled configurations, to verify the operation of the cathodes and validate the numerical model. The comparison between experimental and theoretical results are presented, offering a sound framework to drive the design of future hollow cathodes.

Background Pressure Effects on the Performance of a 20 kW Magnetically Shielded Hall Thruster Operating in Various Configurations

“…It must be said that the HT20k M retains the same channel dimensions of the HT20k DM1, and all three configurations have the same channel mean diameter as the DM1. The HT20k DM2 Hall thruster is coupled with the SITAEL HC60 high-current hollow cathode [43], which provides the electrons necessary to maintain the discharge and to neutralize the accelerated ion beam from the thruster.…”

Electron properties of an emissive cathode: analysis with incoherent thomson scattering, fluid simulations and Langmuir probe measurements

“…⃗ j e = −enµ e ∇ϕ + µ e ∇p e (8) with the electron pressure p e = nk B T e and the electron mobility µ e = e/mν e , and charge conservation is written as:…”

Ion Thruster Operation with Carbon Nanotube Field Emission Cathode

“…The electron emission cost was 360 W/A. This is higher than that of a conventional hollow cathode (less than 30 W/A) [26,27], but considering the current range and the lack of propellant consumption, this is a competitive cost. A remaining challenge is demonstration of the 30 W class miniature ion thruster with CNT-FEC and the life expectancy of the FEC with carbon nanotube.…”