At the beginning of the project, a science work plan and an industrial work plan were collaboratively designed to organise the research and the technical development of the product. The industrial consortium’s expertise, especially OHB’s, allowed to define the target product and the required specifications.
Much information about mission analysis and satellite interface were exchanged to offer a relevant architecture for the whole module. The main idea was to design a modular PJP, by developing building blocks (which can be developed and qualified independently).
The performance of the electronics was improved thanks to an innovation that also made it possible to miniaturize its volume. The standard configuration has an overall volume of 0.7U and a mass lighter than 1kg, making the PJP one of the world's most compact propulsion systems.
Thanks to the scientific consortium, we succeeded in consolidating the propulsive performances of the PJP and improving its thrust duration (total impulse). The PJP can now carry out station-keeping missions over several years.
The development strategy was to run cycles lasting several months to create different prototypes. The first step was a brainstorming session where innovative concepts were shared. Next came computer-aided design (CAD) of the prototype, followed by manufacturing. Once integrated, the prototype was tested and characterized, and we then carried out a detailed analysis of the causes of failure, as well as the positive points, which we used to find areas for improvement for the next prototype.
Since the consortium's inception in 2020, 5 different prototypes have been designed and tested with the aim of increasing the thruster's service life and achieving the defined target. The various concepts have enabled us to explore and gain a better understanding of the erosion phenomena involved in vacuum arc physics. At the end of the project, even if the total impulse (i.e. life duration) of the thruster has only reached 20% of the objective, it has been multiplied by a factor of ten since the beginning.
The Plasma Jet Pack's pulsed operation means that measurements can only be made during the pulse, which lasts a few tens of microseconds. This brevity makes measuring the plasma's physical parameters all the more complex. Icare, Laplace, and the Bundeswehr University of Munich thanks to their specializations, have set up different means of measurement and were able to determine various parameters such as density, ion velocity, ion charge and distribution, electronic temperature, etc. A major result is that the ion velocity (15 to 50km/s measured by Icare and Laplace) and thrust (measured by Comat) are higher than in a classical Vacuum Arc Thruster, and these attributes are the result of the PJP operating point. For the first time, plasma parameters have been measured as function of the time discharge.
Before the PJP's development, investigations were mainly experimental. Another objective of this project was therefore to develop a numerical model that could simulate the exhaust plasma behaviour in different configurations. The model developed by PlasmaSolve in that frame draws the plasma jet with and without magnetic field in 2D and 3D with some approximations from the cathodic region. Several forecasts were done and confrontations with experiments proved to be consistent.
In total, a dozen presentations about the PJP technology were given around the world and eleven scientific articles were published.
