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Development and Test of a plasma Bridge Neutralizer based on Radio-Frequency Ionization for Electric Propulsion Applications

Programme Reference
Prime Contractor
Leibniz-Institut f?r Oberfl?chenmodifizierung e.V.
Start Date
End Date

The objective is to develop a cathode-less neutralizer for EP thrusters to overcome lifetime issues and handling problems present with existing neutralisers.


North-South station keeping, orbit raising, deep space missions and formation flying of two or more spacecrafts are domain of electric propulsion (EP). Development of neutralizing element - a necessary thruster system compaonent- with high life time, low power consumption and high reliability is the same challenge like the thruster development itself.Having a neutralizing element is mandatory. During ion thruster operation, poisitve ions are extracted from plasma on different principles dependant on the thruster type. Thereby a positive space charge is formed around the thruster, and the thruster body respectively the satellite becomes negatively charged. to encure proper operation of the thruster and to reduce the risk damage of satellite components by energetic ions the leaving positive charges have to be compensated by provided by a neutralizer system.Several types of neutralizer have been developed in the past such as hot cathode neutralizers, plasma bridge neutralizers with hot cathode or hollow cathode and bipolar grid system switches. Neutralizers with a hot or a hollor cathose are known to have a limited lifetime and/or reliability.A cathodeless radio-frequency (RF) neutraliser would overcome most of the lifetime and handling problems. Indeed no external heating is necessary, nor hot parts like tungstem filaments or sensitive inserts. No component is sensitive to ambient gases and the design is robust.Because of the large operation time, the low maintenance effort and low beam impurity a cathode-less RF neutralizer would be an interesting alternative to frequently used hot-filament or hollow cathode neutralizers.In previous research and development activities the capabilities of RF-neutralizer have been demonstrated. A generic design of an Elegant Breadboard (EBB) RF- neutralizer (current up to 1.8 A) has demonstrated its performance and readiness for the next step toward an engineering model together with a well defined thruster system (RIT-22). Studies dealing with the functionality and the RF-neutralizer lifetime were completed.However optimisation of the concept towards higher efficiency is mandatory. Moreover no test under environmental conditions embedded in a complete electric propulsion system was performed.This activity aims at developping a breadboard model of the neutralizer capable to withstand meachnical loads during a launch and capable to operate under typical space conditions. Analytical models shall be eleborated. Experimental activities to validate the models shall be performed with and without a dedicated thruster.

Application Domain
Generic Technologies
Technology Domain
19 - Propulsion
Competence Domain
7-Propulsion, Space Transportation and Re-entry Vehicles
Initial TRL
Target TRL
Public Document