Popular Science by Rob Verger 6/23/2023
The decision not to fly the experimental X-57 came about because the agency discovered that the propulsion system had the potential to fail and put people at risk. 
The X-57 in 2021. NASA/Lauren Hughes
NASA said today in a conference call with reporters that it would not ever be flying its experimental electric aircraft, the X-57, citing safety concerns that are insurmountable with the time and budget they have for the project. The X-57 program will wind down without the aircraft ever going up into the sky.
The agency had previously hoped to fly the aircraft, which would be powered by batteries and electric motors, sometime this year. While the original plans had called for the research plane to eventually have more than a dozen propellers, NASA had scaled back those plans too, intending to fly the plane in what they called Modification 2 form. Mod 2 involved the plane having just two propellers, with one on each wing. The news today means that the plane will never fly, not even in Mod 2 form.
NASA said that the reason behind permanently scrubbing the flight is safety and time. “Unfortunately, we recently discovered a potential failure mode in the propulsion system that we determined to pose an unacceptable risk to the pilot’s safety, and the safety of personnel on the ground, during ground tests,” Bradley Flick, the director of NASA’s Armstrong Flight Research Center in California, said in the call. “Mitigation of that failure would take the project well beyond its planned end at the end of this fiscal year, so NASA has decided to end the project on time without taking the vehicle to flight.”
More:
https://www.popsci.com/technology/nasa-cancels-x-57-flight/
