Jun. 29—NASA is grounding an all-electric aircraft before its inaugural flight, ending a program that struggled to shoehorn existing technologies into a broader effort that would curtail greenhouse gas emissions.
But the agency is continuing to research hybrid electric propulsion systems and a new wing design that could make commercial carriers more fuel efficient. And other companies are working to develop such technologies, including flying taxis, which could be in Houston by the end of the decade.
Engineers were racing toward one flight test of the X-57 Maxwell before the program is scheduled to officially end in September. The team recently discovered a mechanical issue with the motors — and it posed an unacceptable risk that could not be overcome in the coming months.
"We're in the flight test business, and we're not going to have flight tests," Bradley Flick, director of NASA's Armstrong Flight Research Center, said during a news conference last week. "So of course there's disappointment. But that does not diminish from the game-changing lessons that this project team has contributed to the industry."
The X-57 team has published more than 100 technical papers, and it helped create a foundation for electric aviation standards and regulations.
The program's end also indicates that batteries are not the solution for large passenger planes, at least not for the foreseeable future, said Pat Anderson, an electric propulsion researcher and professor of aerospace engineering at Embry-Riddle Aeronautical University.
"We're starting to see people that were really bullish on battery electric airplanes not able to actually pull it together, even at a small airplane scale," Anderson said. "We are just a really long way off from being able to use batteries to move commercial aircraft."
Commercial airlines are striving for net-zero greenhouse gas emissions by 2050.
United Airlines, the largest carrier at Bush Intercontinental Airport, has invested in electric air taxis that could become operational in 2026 to transport up to four people from places like downtown Houston to the airport. It has also invested in hybrid electric aircraft that could start flying in 2028 on regional flights to small, currently underserved Texas cities.
'Next generation of helicopters'
The most immediate benefit of electric propulsion will be creating new types of aircraft, Anderson said. This includes the flying taxis that take off and land vertically with a range of about 25 miles.
"They are, in a way, the next generation of helicopters," said Henry Harteveldt, a travel industry analyst at Atmosphere Research Group.
But these vehicles would have several smaller rotors instead of one large rotor at the top. This increases safety because one rotor can go out and the vehicle can still land.
The aircraft can also be quieter, which is important as companies hope to fly rooftop to rooftop in big cities.
"We can't have 10,000 helicopters flying around the city," Anderson said. "People would go crazy over noise."
There will likely be other uses for this technology before regulators approve flying taxis. Anderson believes they will first be used by the military, likely moving cargo before flying people. Then he expects to see shipping companies fly boxes.
'A big yawn'
Not all electric vehicles will resemble helicopters. The X-57 team planned to develop a plane with smaller wings and 14 electric motors and propellers.
The smaller wings intrigued Anderson because they could help a plane use less energy when cruising between destinations. This technology could also enable aircraft to take off and land with less pavement, potentially enabling rooftop runways.
NASA intended to reach this design through an iterative process. But it got stuck in one of the earlier iterations, where the team was trying to swap a traditional plane's combustion engines with an electric propulsion system. The plane NASA hoped to fly this year, a modified Italian Tecnam P2006T, had normal wings and two electric engines.
"It became a pretty plain Jane vehicle," Anderson said. "If they actually flew it, this would be a big yawn. They got rid of a lot of the interesting aerodynamics."
Vincent Schultz, the X-57 deputy project manager, said the plane was never meant to be a prototype for some future electric aircraft. It was designed as a test platform that would build up the industry.
The team also discovered that a lot of the technology they needed wasn't developed enough for an aircraft.
"We've been building electric motors and batteries for over 100 years. How hard could that be?" asked Flick, director of NASA's Armstrong Flight Research Center. "There was a belief that the technologies were more ready than they proved to be."
The X-57 program was initially expected to cost $40 million. But as of August 2022, it had incurred costs of $87 million (and was budgeted for a total of $99 million through the end of September 2023). The program needed another $64 million to complete the project by 2027, according to the NASA Office of Inspector General.
NASA's current budget is $25.4 billion, with $935 million devoted to aeronautics. NASA could not justify the additional X-57 costs because it had determined all-electric flights would help only a small part of the commercial aviation sector.
Harteveldt, the travel industry analyst, viewed the program's end as a consequence of government deadlines and funding — not because the team failed.
"I think the industry will be disappointed that NASA won't be able to finish this project," Harteveldt said. "I won't be surprised if private companies come to work with NASA to learn from them. Because the industry wants to be sure that they don't repeat the same mistakes."
Ultimately, Anderson said battery technology is not advanced enough for large commercial planes. Batteries are 20 to 26 times heavier than traditional fuels even when considering electric airplanes are more efficient. Heavier planes wouldn't lift off the ground — or they would require removing all the people and cargo to become airborne.
"That is just a tremendous thing to overcome," Anderson said, "because weight is probably the single most important design variable."
Creating fuel from corn grain and algae
As an alternative, airlines are beginning to use sustainable aviation fuels created from corn grain, algae and other resources. This could be used in conventional combustion engines.
Airline tickets will likely be more expensive as the supply ramps up to meet demand. But Anderson believes these prices will level out sooner than electric battery technology will mature.
Still, there is a future market for electric aircraft. Billions of dollars from outside the aeronautics industry has flown into electric propulsion and advanced air mobility, Anderson said, and he co-founded the electric propulsion company VerdeGo Aero in 2017. He's particularly bullish on hybrid technologies.
"I believe that electric motors, rotors and other electric components will enable new missions that cannot be flown with existing aircraft," he said. "This is just like how the jet engine enables airplanes to do what the old piston propeller airplanes could not."
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