Javier Torres is technical manager at Airbus Crisa and his main role is to supervise and coordinate all engineering tasks during the development of a product. His work usually starts with the requirements analysis and architecture definition and I follow closely all the development until the production of the first flight units to ensure that we delivery, on-time, a high-quality product that meets all its performances. As GIESEPP MP is a consortium of several organisations, it is also important to coordinate all the tasks and workflow with the rest of the partners.
What is Airbus Crisa contribution to GIESEPP MP?
Within GIESEPP MP we are in charge of developing the PPU, or Power Processing Unit, for a new European electric propulsion system based on the Gridded-Ion thruster RIT 2X. Our expertise on designing and manufacturing flight worthy electronics for space applications, gained during the last forty years is key to bring the know-how necessary to develop a very competitive propulsion system for GEO and MEO missions.
Could you explain us first what is a PPU and how does it work?
The PPU is the unit in charge of controlling the propulsion system and delivering the electric power to the thruster. It is therefore a power electronic unit that transforms the power coming from the satellite distribution lines to supply the different parts of the thruster, but also a control unit which is monitoring all parameters of the system and performing the necessary control sequences to have fully-autonomous operation with minimal intervention from the satellite on-board computer.
Is your PPU only compatible with one thruster?
GIESEPP MP is focused on Ariane Group’s RIT 2X thruster, but our PPU product has the design flexibility that allows it to be configured to operate several types of thrusters and propellant regulation subsystems. Its architecture has been conceived in a such a way that power supplies that are specific to a type of thruster can be easily removed or interchanged by others, while the power supplies typically present in most electric thrusters are designed for an envelope of conditions to favor its reuse. We also include our own embedded microprocessor where specific software sequences and parameters to control the system can be configured, which give us a lot of flexibility.
How long does an electronic equipment like the PPU endure in space?
In GIESEPP MP we have defined a mission target of 15 years in orbit. This lifespan comes from the market analysis that Airbus has performed, where GEO telecom missions have been identified as the segment where more growth is forecasted for the upcoming years. A 15 years lifespan ensure us that we will be able to cover all these missions.
Our unit it also compatible with other types of scenarios, like exploration missions, where we think that GIESEPP MP electric propulsion system can bring significant advantages due to its high specific impulse and the potential fuel savings that we can provide respect to other technologies like hall effect thrusters.
Currently, you are designing the PHVM, what is its function?
PHVM stands for “Positive High Voltage Module” and it is probably the most important module within the PPU.
The PHVM supplies most of the electric power to the thruster, where is mostly transformed into thrust by the ejection of low-mass particles at high speed. For the RIT 2X thruster this power is delivered to the screen grid, which requires a high voltage, between 800V and 1500V at 5kW, for its operation.
As the PPU is a complex unit and developing a groundbreaking new generation like this one requires a lot of engineering effort, we have first focused on the PHVM but we are already developing all the other modules in another European initiative called DEEP PPU and we will soon have a full unit ready to be integrated.
What makes it different and which are the cutting-edge technologies that you are using on the PHVM?
Well, there are several features that make this design remarkable.
First, is the use of commercial components (COTS) and the adoption of a more industrial approach. The use of COTS requires a specific process already developed by Airbus that defines the screening and testing of commercial EEE components, as well as the validation of assembly methods to ensure that the selected components will have the required reliability in harsh space environment.
Then there is the use of state-of-the-art technologies like GaN transistors, planar transformers and digital control, which allow us to achieve higher efficiencies and higher power densities. The improvement in power density, or volume, respect to the previous generation of PPUs has been outstanding. The new PHVM is able to deliver the same power, or even more, than the previous one, and it only takes up a third of its volume.
And lastly, I would remark, the novel architecture of the power supply that allows to operate in a very wide range of voltages and currents while maintaining a good efficiency. This is one of the key elements that allow us to operate thrusters of different technologies. We can provide between 2 kW and 3 kW per PHVM and we can do it at any voltage between 200V and 1500V with a top-notch efficiency and good dynamic behavior.
Please, tell us the most significant challenge designing PHVM.
The optimization of the control of the power converter has been challenging, as the converter topology was quite new for us, but I would highlight the design for high voltage as the most challenging one.
We want to have a unit that is able to operate at critical pressures, around a few Pascals, to be able to provide thrust at low altitudes for orbit raising maneuvers. Achieving a good isolation at these pressures it is not easy, especially when you have high dissipative elements that require a good conductive path. Electrical isolation implies distance and this is contrary to a good thermal conductivity. On top of this, we did not want insulation techniques that were difficult to manufacture, so we have had to think outside the box.
We are still validating the final assembly, but we are quite happy with the results that we have obtained so far.
Thank you, Javier Torres, for sharing these fascinating insights into the cutting-edge technology behind the Power Processing Unit (PPU) and its key role in the future of European electric propulsion systems. It’s clear that the innovative work being done by Airbus Crisa and the GIESEPP MP consortium is setting the stage for a new era in space exploration, combining flexibility, efficiency, and longevity in space missions.
