The DEEP PPU project represents an important step forward in Europe’s ambition to develop a new generation of Power Processing Units (PPUs) for electric propulsion. During a recent webinar, Javier Torres, Technical Manager at Airbus Crisa, provided an in-depth look at the project’s progress — from defining mission requirements to building and testing an advanced engineering model that sets the foundation for future flight units.
A new generation of Power Processing Units
The Power Processing Unit (PPU) plays a crucial role in conditioning and managing the electrical power used by spacecraft systems. The goal of the DEEP PPU project is to design a more efficient, compact, and cost-effective PPU, building upon previous models to increase performance, integrate new functionality, and enhance competitiveness in the market.
Airbus Crisa has led the design and coordination of the PPU development, focusing on delivering a high-performance, flight-representative engineering model that can validate the design before entering the qualification and production phase.
From requirements to architecture: building a smarter system
Every space system begins with rigorous requirements. For the PPU, these were grouped into three main categories:
- Mission requirements: ensuring performance and reliability for a 15-year operation in geostationary orbit, withstanding environmental challenges and launch conditions.
- System requirements: guaranteeing compatibility with spacecraft subsystems, particularly the RIT2X thruster, one of the leading European radiofrequency ion thrusters.
- Internal Airbus requirements: ensuring manufacturability, cost efficiency, and flexibility to support various thruster types and mission profiles.
One of the key innovations of the DEEP PPU is the integration of the Radio Frequency Unit (RFU) directly inside the PPU. Traditionally, the RFU is located externally, but integrating it internally allows for a more compact and streamlined design, simplifying spacecraft integration and reducing overall mass and volume.
Engineering the architecture
After the requirement phase, the engineering team defined an optimized system architecture through detailed trade-off analyses — comparing design options for cost, mass, production time, and efficiency. The final configuration includes:
- FCC Module: The “brain” of the PPU, responsible for high-level control and providing generic power supplies that can be used for the cathode and the fluidic system.
- PHV Module: The power module, delivering up to 1.5 kV and capable of operating across a wide voltage range with high efficiency.
- Thruster Specific Module: Designed for the RIT2X thruster, incorporating the accelerator grid supply and the new integrated radiofrequency generator.
Design and validation: where theory meets reality
Developing such a complex system requires multidisciplinary collaboration. Specialized teams of electrical, software, microelectronics, thermal, and mechanical engineers worked in parallel to design, simulate, and test every subsystem.
Breadboarding was a critical step in this process — manufacturing early prototypes to test converter topologies, high-voltage assemblies, and component durability under operational stress. These early validations help reduce risk and confirm performance where simulations alone cannot.
Thermal, mechanical, and electrical analyses ensured that all components could operate safely under launch vibration, radiation exposure, and thermal cycling. Once the design was finalized, Airbus Crisa built an engineering model that mirrors the flight unit’s design and functionality but uses lower-grade components for testing efficiency.
Testing for performance and reliability
The engineering model underwent extensive characterisation and integration testing, examining power conversion stability, digital timing, and system-wide compatibility between FPGA-based control logic and software.
For flight qualification models, even more rigorous tests — including vibration, shock, vacuum, thermal, and electromagnetic compatibility — will follow. Additionally, coupling tests are essential to validate the PPU’s performance with a real or simulated thruster. Since plasma behaviour can be difficult to predict, these tests provide invaluable data for refining the design.
Achieving the targets
The DEEP PPU team has already reached several of its main goals:
- Achieved mass and volume reduction targets.
- Reduced production costs compared to previous models.
- Successfully integrated the radiofrequency generator within the PPU.
- Reached maturity level suitable for transition to flight unit production.
As Javier Torres concluded:
“We have achieved the targets we set at the beginning — in mass, volume, cost, and design maturity. The engineering model validates our approach, and we are now ready to move toward qualification and flight production.”