El fly - NASAs X-fly går mot hybrid og el drift - AW&ST

Electrification Sparks Rethink in NASA X-Plane Plans Guy Norris and Graham Warwick  NASA has had to be creative in its bid to return to manned X-plane flight research within a constrained budget. Its first move was the relatively modest X-57 Maxwell, an electric propulsion demonstrator based on a light general-aviation aircraft that is now expected to fly in 2019. The next step is much bigger: the X-59 QueSTT low-boom flight demonstrator. The program passed a key decision point in November,  and the aircraft is expected to fly early in 2022. But to fit this clean-sheet X-plane into its budget, NASA had to split the program into two, awarding Lockheed Martin Skunk Works a preliminary design contract in February 2016, then competing construction of the demonstrator. Lockheed won, receiving a $247.5 million contract to build the X-59 in April 2018. NASA seeks industry ideas on next X-plane Hopes to begin new program in fiscal 2021 With the X-57 and X-59 making progress, NASA is now looking toward its next large-scale X-plane program. The agency thought it knew what it wanted to do, and funded four companies to propose ideas for experimental aircraft to demonstrate new configurations for future fuel-efficient subsonic airliners. Five different concepts were presented in 2017, but recent rapid advances in electric propulsion technology have NASA’s leadership rethinking their next steps. Commenting on the potential change in direction on future X-planes, Jaiwon Shin, NASA associate administrator for its Aeronautics Research Mission Directorate, says: “We thought electrifying aircraft would be the holy grail at the very of end of this transformation of the large transport-category aircraft market, but it is actually progressing and has moved up quite a bit. The industry is really interested, and they think it is doable much sooner rather than later.” The original plan, outlined in the New Aviation Horizons flight demonstration initiative within NASA’s budget request for fiscal 2017, called for a series of Ultra Efficient Subsonic Transport (UEST) X-planes to follow the X-57 and X-59 and fly from fiscal 2023 onward. NASA did not receive the required funding, but the first in the series were to focus on unconventional aircraft configurations. A large-scale hybrid-electric propulsion demonstrator was not planned to fly before fiscal 2025 at the earliest.

One of the subsonic X-plane proposals presented in 2017 was this Boeing transonic truss-braced wing concept based on an MD-80. Credit: Boeing

Increased urgency for development of hybrid-electric propulsion technology has been triggered by Airbus and Boeing, says Shin. Both have signaled the requirement for nearer-term low-emissions propulsion systems for the next major single-aisle airliner replacement cycle. “It’s mostly driven by the fact they have learned that, after development of the A320neo and 737 MAX, they have to come up with some new propulsion systems. That’s unless they really want to change the aerodynamics with a completely different configuration, which may not be in the cards,” he says. This revised focus has stimulated electric motor, battery and related advances throughout the industry faster than NASA or the major manufacturers anticipated. “That’s probably why, in the transport category, they think maybe they can bring a hybrid-electric propulsion system in sooner rather than later,” says Shin. “Airbus is actively moving out, and I think Boeing, which has invested in Zunum, is putting a lot of effort in there, too,” Airbus is building the E-Fan X hybrid-electric regional demonstrator while Zunum is developing a 12-passenger hybrid aircraft. “That kind of changed the game plan. We were thinking of this complete departure from tube-and-wing-type configurations, and that this would probably have been the next UEST X-plane. But that may not be the case,” says Shin, referring to the unconventional blended-, truss-braced and joined-wing candidates that until recently have been front-runners in consideration for further development. “We are carefully discussing with our industry partners to see what might be the most compelling and important UEST.” That dialog included one-on-one meetings with interested companies at an electrified aircraft propulsion industry day held in the Washington area on Dec. 6. Results from the meeting, and a parallel request for information, will feed into work to frame NASA’s fiscal 2021 budget request, which will get underway in January, says Ed Waggoner, director of NASA Aeronautics’ Integrated Aviation Systems Program (IASP). “At the end of the previous administration we had plans to do a number of X-planes. We knew it was a lame duck budget, but it gave us the authority to put together a good set of plans. We were successful in getting funding for the X-59, and now we look forward to perhaps having the budget support for a second X-plane,” he told the industry-day attendees.

Startup Wright Electric has briefed NASA on its M-wing all-electric airliner concept. Credit: Wright Electric

NASA is in “discovery mode,” says Waggoner. “We are here to listen, to understand from industry’s perspective what the potential is for more electrified propulsion. This is not a precursor to a solicitation. We want to understand where industry is in development and what its key research needs are. We want to understand what the key technologies are to enable electrified propulsion for subsonic fixed-wing transports . . . and see how they overlap with what NASA plans.” The agency’s focus is on demonstrating a 1-megawatt-plus electric propulsion capability, says Fay Collier, associate director for flight strategy within IASP. Industry has indicated that a megawatt-class system could find several applications: one could power a small regional airliner; several could power a larger aircraft with distributed electric propulsion. A megawatt-class motor could drive a tail thruster, enabling drag-reducing boundary-layer ingestion, or be integrated into a turbofan engine to provide electric boost in a hybridization approach that studies suggest could improve energy efficiency. NASA already has funded several research teams to develop megawatt-class electric machines and power electronics and, depending on budget, could demonstrate a 1-megawatt-plus capability within three years of program start, says Collier, who adds: “Whether we fly or not is to be decided.” The range of possible uses for a megawatt-class system also means a range of demo options. “When we started the low-boom flight demonstrator we didn’t have the budget, so we divided it into two procurements. If we do another X-plane we hope not to have to do that: just one competition and one procurement,” Waggoner told industry-day attendees. “Whether it is a small focused demonstration or a full-up demonstration, that is the point of this interaction.” NASA’s potential change in direction on its next X-plane comes amid positive signs that its aeronautics budget is set to remain at or above $700 million a year. At the same time, several big-ticket research efforts are due to end by 2020. These include major projects such as unmanned traffic management, unmanned aircraft system integration into the national airspace system, and the agency’s advanced composites program. “So we want to not just continue the same work, but redirect some of these resources,” says Shin.