NASA has issued an award to The Boeing Company for the agency’s Sustainable Flight Demonstrator project, which seeks to inform a potential new generation of green single-aisle airliners. Under a Funded Space Act Agreement, Boeing will work with NASA to build, test, and fly a full-scale Transonic Truss-Braced Wing (TTBW) demonstrator airplane.

The Transonic Truss-Braced Wing concept involves an aircraft with extra-long, thin wings stabilized by diagonal struts. This design results in an aircraft that is much more fuel efficient than a traditional airliner due to a shape that would create less drag—resulting in its burning less fuel.

Artist concept of commercial aircraft families with a Transonic Truss-Braced Wing configuration from the Sustainable Flight Demonstrator project. Credits: Boeing

When combined with expected advancements in propulsion systems, materials and systems architecture, a single-aisle airplane with a TTBW configuration could reduce fuel consumption and emissions up to 30% relative to today’s most efficient single-aisle airplanes, depending on the mission, according to Boeing.

The technologies demonstrated and tested as part of the Sustainable Flight Demonstrator (SFD) program will inform future designs and could lead to breakthrough aerodynamics and fuel efficiency gains.

Over seven years, NASA will invest $425 million, while the company and its partners will contribute the remainder of the agreement funding, estimated at about $725 million. As part of the agreement, the agency also will contribute technical expertise and facilities.

Separately, Boeing’s previous internal investments for recent phases of sustainable aviation research total $110 million.

It’s our goal that NASA’s partnership with Boeing to produce and test a full-scale demonstrator will help lead to future commercial airliners that are more fuel efficient, with benefits to the environment, the commercial aviation industry, and to passengers worldwide. If we are successful, we may see these technologies in planes that the public takes to the skies in the 2030s.

—NASA Administrator Bill Nelson

Background. TTBW has been in continuous development since 2008. The significant increase in the wing aspect ratio is expected to result in a significant decrease in induced drag. The aspect ratio of a wing—a measure of how long and slender a wing is from tip to tip—is defined as the square of the span divided by the wing area. High aspect ratio wings have long spans (like gliders), while low aspect ratio wings have either short spans or thick chords (the distance from leading edge to trailing edge).

Structural efficiency for the longer, more slender wing is provided by the strut bracing, which decreases wing root bending moments.

There are a number of development challenges, as outlined in the slide below from a 2021 presentation by a Boeing / NASA research and development team:

Single-aisle aircraft are the workhorse of many airline fleets, and due to their heavy usage, account for nearly half of worldwide aviation emissions. NASA plans to complete testing for the project by the late 2020s, so that technologies and designs demonstrated by the project can inform industry decisions about the next generation of single-aisle aircraft that could enter into service in the 2030s.

The project is an activity under NASA’s Integrated Aviation Systems Program and a key element of the Sustainable Flight National Partnership, which focuses on developing new sustainable aviation technologies.