Airbus has launched the “Advanced Superconducting and Cryogenic Experimental powertraiN Demonstrator” (ASCEND) to explore the impact of superconducting materials and cryogenic temperatures on the performance of an aircraft’s electrical propulsion systems.

The introduction of superconducting materials can lower electrical resistance; thus, electrical current can supply power without energy loss. When coupled with liquid hydrogen at cryogenic temperatures (-253 degrees Celsius) electrical systems can be cooled in order to increase the performance of the overall electric propulsion system significantly.

ASCEND. A ground demonstrator to explore the feasibility and application of “cold” electrical technologies for low-emission aircraft propulsion.

One of the major challenges of scaling up electric propulsion to larger aircraft is the power-to-weight ratio. In other words, today’s electrical systems simply do not meet the necessary power requirements without adding excess weight to the aircraft. But high-temperature superconducting technologies are emerging as a possible solution to this technical conundrum, notably by increasing power density in the propulsion chain while significantly lowering the mass of the distribution system.

The three-year ASCEND project aims to show that an electric- or hybrid-electric propulsion system complemented by cryogenic and superconducting technologies can be more than 2 to 3 times lighter than a conventional system—through a reduction in cable weight and a limit of 30kW/kg in power electronics—without compromising a 97% powertrain efficiency.

To achieve this objective, ASCEND features a 500kW powertrain consisting of the following components:

• A superconducting distribution system, including cables and protection item;

• Cryogenically cooled motor control unit;

• A superconducting motor; and

• A cryogenic system.

In addition to optimizing the weight of the distribution system, another objective of ASCEND is to increase significantly the power density of the propulsion chain. This is a key consideration, as increasing the power of current electrical aircraft systems from a few hundred kW to the MW required for a fully electric aircraft is not easy. More power increases weight and installation complexity, and generates more heat.

However, if a cold source at 20 K (-253.15 °C), such as liquid hydrogen, is available on board, it can be used to cool the electrical systems. The superconducting components can then work to improve the power density of the electric-propulsion systems.

ASCEND will assess electric architectures from several hundred kilowatts to multi-megawatt applications with and without liquid hydrogen on board.

Airbus will design and build the demonstrator over the next three years at its E-Aircraft System House. Solutions that could be adapted to turboprop, turbofan and hybrid propeller engines will be tested and evaluated by the end of 2023. It will support Airbus’ decision making-process for the type of propulsion system architecture required for future aircraft.

ASCEND is also expected to support performance improvements on existing and future propulsion systems across the entire Airbus portfolio, including helicopters, eVTOLs, as well as regional and single-aisle aircraft.

The demonstrator is hosted within Airbus UpNext, an Airbus subsidiary created to give future technologies a development fast-track by building demonstrators at speed and scale, evaluating, maturing and validating new products and services that encompass radical technological breakthroughs.

With the ASCEND demonstrator, we’ll pave the way for a real breakthrough in electric propulsion for future aircraft. The importance of this work can’t be understated: cryogenic and superconducting technologies could be key enablers to enhancing the performance of low-emission technologies, which will be essential to achieving our ambitious decarbonisation targets.

—Sandra Bour Schaeffer, Airbus UpNext CEO

Airbus is already looking into how liquid hydrogen could be used as fuel for an internal combustion engine or fuel cell as part of its ZEROe pre-program. The ASCEND demonstrator will thus complement this research by providing additional insight into how cryogenic and superconducting technologies can support an ultra-efficient electric- and/or hybrid-electric propulsion system for future aircraft.