Airbus Crisa and the design flow for electronic space equipment

Developments in power electronic space equipments projects by Airbus Crisa in GIESEPP MP and DEEP PPU are analysed in detail, examining the processes, analyses and tools used in the aerospace industry, with a focus on a unit developed specifically for electric propulsion applications. This integrated approach provides a full understanding of how developments in power electronics are contributing significantly to the growth and innovation of the aerospace industry.

The role of Airbus Crisa in the DEEP PPU project

Airbus Crisa is responsible for the development of the PPU (Power Processing Unit). In the field of electric propulsion, the PPU is the power management equipment in charge of supplying the power to the whole propulsion system and also controlling it. It gets the power from the spacecraft batteries or solar panels and converts it into the power required to supply energy to the passive elements of the electric propulsion system, such as the thruster or fluidic control valves, including safety features such as over-current, over-voltage and over-temperature protections to ensure that the engine and spacecraft are protected from any damage in the event of a failure.

In addition to its primary conversion function, Airbus Crisa’s PPU also performs power regulation, adjusting voltages based on the thruster’s operating point, and power conditioning, including noise removal from specific frequency bands to ensure stable behaviour. The PPU also reads telemetries and provides control to operate the thruster, such as pulse-width modulation and frequency control.

What are the primary objectives?

The primary objectives of the design process includes developing the equipment considering electrical requirements, schedule, and cost constraints. It is essential to ensure the quality and reliability of our design and to optimise manufacturability in terms of the number and type of components. In addition, it’s important to minimise the risks of having to make changes at the start of production in later stages.

The PPU and the main challenges for Airbus Crisa

The primary target of this project is to achieve a high volume of units at a competitive price without compromising the performance and reliability of the end products. The proposed requirements for this endeavour are quite demanding in the business context, adding complexity to the project. For instance, a crucial requirement is that the high-voltage module must deliver up to 1.5 kV to the engine, which is a stringent specification. In addition, the project operates in the space environment, which presents:

• thermal challenges: these include the absence of conventional heat convection mechanisms, caused by the vacuum of space.
• presence of radiation.
• potential vibrations.

To overcome these challenges, the project is using advanced technologies, including the use of commercial off-the-shelf components and gallium nitride semiconductors. This approach has a dual effect: it reduces both the mass and volume of the device, resulting in cost savings.

Cost-cutting solutions

Speaking of cost reduction, the project is also exploring a departure from the traditional Power Processing Unit (PPU) architecture. In the traditional design, certain functions, such as the radio frequency generator, are implemented in separate units before being integrated into the main unit. The project aims to streamline this integration process, reducing the overall integration effort and cost of the unit. Finally, the program places a strong emphasis on optimising the efficiency of the power system while minimising thermal losses.

The main stages of electronic equipment

Within the electronic design process, it is interesting to note that three fundamental phases clearly emerge, and it should be emphasised that each of these main phases is further articulated into several specific sub-phases. This detailed delineation plays a crucial role in guiding and structuring the multiple procedures involved in the conception and development of electronic design.

1. The initial stages are represented by the requirements and specification phases. Within these phases, it is crucial to consider the market analysis, the platform needs, and the thruster characteristics, as well as the internal requirements. The outputs to be considered are modularity, interfaces, and unit specifications.
2. In the preliminary design phase, the primary objective is to assess the feasibility of the system and identify potential risks. The system’s components and topologies, budget constraints, materials and processes are taken into account, and a mechanical model is created. At Airbus Crisa, customised and optimized tools are developed in order to meet the very specific needs through the different stages of the design process. It is essential that the selected components perform reliably throughout the mission, so they undergo a qualification process. During the development of the architecture phase, module maturity must be achieved, and a preliminary design overview is required.
3. In the detailed design phase, strict adherence to electrical requirements is essential. Any previously developed budget is now refined. A Failure Mode Analysis is also carried out, the main purpose of which is to identify potential failures. It must also be proved that every single component is operating below its specified maximum ratings. A reliability analysis is also carried out to ensure that the PPU will meet the maximum failure rate over its lifetime. Once all these analyses have been completed and compliance has been demonstrated, the design is validated, and the procurement, PCB design, and model manufacturing stages can begin.

Concluding design steps up to the launch

Following design, the next steps for this module include qualification of the unit once all the modules have been integrated. This is followed by a series of flight acceptance tests. At this point, the design is delivered, and the customer takes the next steps, which include integration of the system into the satellite and, finally, launch. For this operation, a distinction can be made between electrical models, qualification models and flight models. The first two stand for system performance and system qualification, while the flight model is the one that will actually be launched. The new trend in Airbus Crisa’s work is also to improve processes and keep developing the most suitable space equipment solutions, extensively proving the reliability of the units.