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Plasma Jet Pack

Periodic Reporting for period 2 - PJP (Plasma Jet Pack)

Reporting period: 2021-01-01 to 2021-12-31

This project proposes to develop a disruptive electric propulsion module technology called “Plasma Jet Pack” (PJP) based on the vacuum arc physics.
By using the propellant as a solid metal state, this storage solution allows to largely reduce both the volume and the complexity of the overall propulsion module.
The main advantage of this technology is the capability to thrust on demand from -50°C to 70°C without any preheating phases. Another asset is its power flexibility, by offering an adjustable thrust between 0 and 30W without any change in efficiency.
The consortium aims at achieving the validation and commercialization of this module at the end of the project. The H2020 team consists of experts from space propulsion, space hardware development and vacuum arc physics.

In parallel of this development, an in-orbit demonstration will be performed on a 6U platform led by ISIS Space (December 2022), in order to compare the on-ground measurements to those in-orbit (thrust, temperatures, ignition rate, etc.).

The main objective of this project is to qualify the first Plasma Jet Pack product for nanosatellite applications and start the commercialization at the beginning of 2023.
At the beginning of the project, a science work plan and an industrial work plan were collaboratively designed to organize the research and the technical development of the product.

Thanks to the industrial consortium expertise (OHB & Thales), the target product and the thruster specifications were defined. Much information about mission analysis and satellite interface were exchanged to offer a relevant architecture for the entire module. The main idea is to design a modular PJP, by developing building blocks. In such a way, building blocks can be developed and qualified independently.
A new DC-DC board design using the “zero voltage switching” has been studied under this project. This innovation will lead to an electronic efficiency above 90% (instead of 60%) using one of the most innovative flyback converter scheme. This new feature will also help miniaturize the overall volume of the module.

Apart from the thruster head, all the building blocks are almost frozen. In the PJP design, the hard task remains our capability to offer sufficient total impulse with a suitable thrust level. Thanks to the scientific consortium, we succeed in consolidating the propulsive performances of the PJP and improving its thrust duration (total impulse).
The strategy was to use an innovation cycle of several months with the following steps: concept generation (brainstorming), detailed Bread Board Model (BBM) design, manufacturing, characterization and failure analysis. Since 2020, five (BBMs) were manufactured, designed and tested in the unique goal to reach the total impulse target. Passive and mobile cathode designs were tested to explore and learn about the erosion mechanism involved in the vacuum arc process. Currently, the total impulse objective is not yet achieved (20% achieved), but the total impulse progress can be evaluated at a factor ten since the beginning of the project.

Despite the difficulty of investigating a “high current-short duration” thruster due to time resolution and instationarity, plasma parameters (density, ion velocity, electron temperature, ion mean charge, etc.) measured by different methods in the laboratories give consistent results. A major result is that the ion velocity (15 to 50km/s) and thrust 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.

A major objective is to develop a numerical model in order to simulate the exhaust plasma jet. Since 2015, COMAT has been adopting a mostly experimental approach because of the difficulty to build and solve a complete set of equations relative to the vacuum arc physics. The model developed by PlasmaSolve in that frame is now capable to draw the plasma jet with and without magnetic field in 2D and 3D with some approximations from the cathodic region. Several forecasts have been done and the confrontations with the experiments are consistent.

In parallel, Comat has developed and qualified a fully representative propulsion module for an In-Orbit Demonstration & Validation mission led by ISIS Space on a 6U platform. The main purpose is to perform a comparison between the on-ground and in-flight measurements of the PJP parameters (thrust, ignition, pulse count, temperature, etc.). COMAT delivered the flight model at the end of 2021 and proved its capacity to produce a miniaturized PJP within a 1U/1kg envelope. The launch is planned for the end of 2022 in a sun-synchronous orbit of 580km altitude. If this mission is successful, COMAT will obtain a flight heritage and increase the Technology Readiness Level of the technology.

Many presentations about the PJP technology have been done around the world or are planned until the end of the project, and no less than seven scientific articles will be published in 2022.
By the end of the project, COMAT will obtain a deeper understanding of the vacuum arc physics applied to space propulsion and a representative numerical model of the plasma discharge. In addition, this consortium has already largely improved the time resolution diagnostic concerning the electrostatic measurement of the plasma plume. This new diagnostic, especially developed for this kind of thruster, can be used for other technologies using the same discharge characteristics. This work allows to access unprecedented measurements such as ion speed, electron and ion temperature, plasma density as function of time for a high current-short duration discharge. These measurements have fed a unique numerical 3D model to predict the Plasma Jet Pack behaviour.

All these results allow to optimize the product design for engineering purposes, and both experimental and theoretical results have been taken into account to build the product architecture.
Plasma Jet Pack