NASA researchers are teaming up with the United States Air Force and industry as part of the NASA Aeronautics Strategic Implementation Plan to continue work on developing a sustainable future for commercial aviation with a goal of reducing fuel burn and thus making airliners of the future more efficient. The work focuses on four core technologies that NASA’s innovators call the four Es: environment, efficiency, electrification, and economy.
“These are technologies that will build from the foundation laid during previous NASA projects such as the Environmentally Responsible Aviation project and studies on future aircraft designs that we called N+3,” said James Kenyon, NASA’s manager for the Advanced Air Vehicle Program. “NASA can invest in the things that are for the greater good, but we don’t build, produce, or operate commercial airplanes. We just develop technologies so that industry can competitively bring these to market as desired.”
In this article published by NASA, their work to produce more efficient airliners is explained, noting that the work is not aimed at creating a future airliner that flies faster than sound, nor is it geared towards small personal air taxi operations or package delivery services. Instead, the focus is on a future airliner that might carry 150 to 175 passengers, flies at subsonic speeds and could supplement or replace aircraft such as the Boeing 737 or Airbus 320 in the 2030 timeframe. “Conceptually, it’s really quite simple,” said Robert Pearce, NASA’s associate administrator for aeronautics. “To lessen our impact on the environment, we must increase aircraft efficiency in every way we can, integrate electrification to aid or replace current propulsion methods, and do it all in a way to benefit the economy.”
NASA said that the same set of technologies that can reduce carbon emissions are those that also reduce fuel burn, which in turn reduces operating costs for the airlines. And if these new airplanes are attractive to the airlines, then manufacturers will want to build them, improving their bottom line as well. “This all lines up our incentives so we can all work together in terms of something good for the climate, for sustainability, is something good for the market, and helps the US maintain its role as a world leader in aviation,” Kenyon said.
NASA’s work centers around four key areas, the first being electrified aircraft propulsion. Fay Collier, NASA’s director for flight strategy in the Integrated Aviation Systems Program explained that plans are to test increasingly more powerful electric systems, up to one megawatt of power, first in a laboratory on the ground, and then later in flight on a testbed aircraft yet to be selected. And Kenyon noted that at the large aircraft level, maybe it’s not fully electric. “If we can use electricity to help out with certain parts of the flight envelope, we can design engines differently and make them more efficient overall,” he said.
The second area of work involves development of small gas turbine engines. NASA is working with Pratt & Whitney and the USAF testing new engine designs with exotic metals, ceramics, and unique internal geometries on the wing of an Air Force C-17. With size limitations on nacelles prohibiting higher bypass ratios, the solution, says NASA’s researchers, is to build turbine engines with smaller core dimensions. “The problem is the nacelle of an engine hanging off the wing of an airliner can only be so big in diameter before it starts dragging on the ground. So, if you can’t make the overall engine wider in diameter, yet you want to increase the bypass ratio so more air flows around the core, then the solution is to make the core smaller in diameter.” NASA’s researchers said.
The Transonic Truss-Braced Wing (TTBW) aircraft concept being developed in conjunction with Boeing has an extremely long and thin high-efficiency wing design with additional trusses to add support. The theory is that a high-aspect-ratio wing generally creates the same amount of lift as the thicker, shorter wings found on airliners today, but does so with much less drag. “We think the TTBW design and associated technology could be ready for manufacturers and airlines to consider using within the 10-year-future timeframe we’re looking at,” Kenyon said.
The last area NASA is working on involves advancements in composite materials to overcome two challenges related to significantly increase the use of composites in larger airliner design. Work is focused on reducing the time it takes to go from concept through design, fabrication, testing and then certification of materials by federal regulators, while the second challenge has to do with increasing the rate at which larger composite structural components can be manufactured. “Design methods to create better modeling capabilities, inspection methods, and processes for automating parts of the fabrication will allow us to reduce the time to certify,” Kenyon said. “What we need now is to come up with ideas for how composites can be manufactured in a way that is reliable, repeatable and results in a quality product that can be routinely certified as safe.”