This activity aims at the evaluation of the long-term grid erosion of two miniaturised Gridded Ion Engine breadboard thrusters in order to satisfy the demands on lifetime and total Impulse required at the thrust profile for the drag force compensation and the attitude control of future Science and Earth Observation missions.

 

Activities on the miniaturisation of GIE thrusters started in 2005 to respond to the need of micro-propulsion systems capable of providing precise thrust modulation in the ?N to low mN regime. Since then, several prototypes have been developed for different applications demonstrating the predicted performance at different thrust levels. In parallel, activities to develop a propulsion subsystem around this type of thruster were initiated in 2009. Prototypes of this subsystem were successfully tested in 2012.

In 2016, a breadboard model of the miniaturized GIE was developed with the latest results from the NGGM preparatory studies which required an increased thrust level ranging from 50 ?N to 2 mN. This activity included the development of an erosion model and a 1000h lifetime test to verify such model.

 

In parallel and since 2003, ESA has promoted studies in order to establish scientific requirements, identify the most appropriate measurement techniques, start the associated technology developments, and define the system scenarios for a Next-Generation Gravity Mission (NGGM). The low-thrust GIE with variable thrust has been identified as one of the key technologies for the realization of the NGGM.

 

In particular, it allows:

• Satellite orbit maintenance at its operational altitude;

• Satellite formation control;

• Implementation of the drag-free control at level of each satellite;

• Attitude control of each satellite.

 

This typology of thruster shall be applicable to many other missions, for EO and Space Science, which require precise attitude and orbit control by means of low-noise force actuators that are widely configurable.

 

This activity is using all previous background on miniaturized GIE models and tests in order to demonstrate two very important topics which are still to be verified: lifetime assessment and interaction of multiple thrusters firing at the same time.

 

Results and models from previous short-duration lifetime tests shall be revisited and used as inputs to define a common erosion model and verification procedures for both thrusters used in this activity. The verification of these topics shall be conducted by running a test campaign where two thrusters operate in parallel, in the same facility and using similar laboratory equipment.

The erosion model and verification test shall allow an independent and confident evaluation of the lifetime and total Impulse provided by each of the miniaturised Gridded Ion Engines.

 

The activity key objectives are:

• To develop a single grid-erosion model to be used for both miniaturised Gridded Ion Engines covering up to 2 mN thrust.

• To evaluate the performance of two thrusters plus their respective RF generators working in parallel.

• To provide expected compliancy to the Science and Earth Observation missions lifetime and total Impulse requirements via a 2000h verification test of the developed predictive erosion model of the Miniaturised Gridded Ion Engines.