The programme will end operations in September, NASA announced on Friday (23 June), cancelling plans for a 2023 test flight.
The project, which started in 2016, encountered “several challenges to safe flight”, the announcement said. These included mechanical issues that appeared late into the modified Tecnam P2006T’s lifecycle, and a lack of available critical components required to develop experimental hardware.
“Given the approaching planned end of aircraft operations, the timeline would not allow the team to reach acceptable flight conditions,” the announcement said.
Despite the cancellation, NASA said the project – which aimed to achieve a five-fold reduction in the energy required for cruising by using distributed electric propulsion across a number of propellers – had achieved many of its goals.
“NASA’s goal is to drive innovation through groundbreaking research and technology development. The X-57 project team has done just that by providing foundational information to industry through lessons learned, and we’re seeing the benefits borne out by American commercial aviation companies that are aiming to change the way we fly,” said Brad Flick, director of NASA's Armstrong Flight Research Centre in Edwards, California, where the X-57 aircraft was developed.
“I’m incredibly proud of their tenacity and ingenuity as they led the way in advancing electrified propulsion. The future of electrified propulsion is possible because of their contributions.”
Rather than developing a prototype, the programme’s aim was to develop a test platform for technologies and design methods. The team documented and published the ‘technology gaps’ that they identified, along with solutions for others in the field to use.
“They did things that had never been done before, and that’s never easy,” Flick said. “While we prepare to finish this project later this year, I see a long list of achievements to celebrate and an industry that’s better today because of their work.”
Areas of focus included electromagnetic interference, motor controller design, and battery technology, which was identified early in the project as needing significant development.
Lithium-ion batteries installed on the aircraft heated up as they discharged energy, which could have led to overheating. The project worked with Electric Power Systems in Utah to address this issue. Engineers demonstrated that the new battery system design would stay within acceptable, safe limits while powering the aircraft.
The design of the cruise motor controllers was another success, the announcement said. The controllers convert energy stored in the aircraft’s lithium-ion batteries to power its motors, which drive its propellers. The controllers use silicon carbide transistors to deliver 98% efficiency, intended for high power take-off and cruise, meaning they do not generate excessive heat and can be cooled off by the air flowing through the motor.
The team designed inverters to meet demanding mass and thermal requirements, and are sharing these designs in technical publications so industry can use them as a launchpad for new products. Most recently, the cruise motor controllers went through successful thermal testing.
During the integration phase, the team encountered electromagnetic interference that affected the operation of onboard systems. After extensive research, they designed, developed, and installed filters that resolved the issue. The approach will be added to the technical papers and shared with industry.
NASA will release additional technical publications in the months following the completion of the project. The agency will continue to research electric aircraft through other projects, including the Electrified Powertrain Flight Demonstration.
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