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Bracing for Fuel-Efficient Flight

This landscape of “mountains” and “valleys” speckled with glittering stars is actually the edge of a nearby, young, star-forming region called NGC 3324 in the Carina Nebula. Captured in infrared light by NASA’s new James Webb Space Telescope, this image reveals for the first time previously invisible areas of star birth.

A new kind of passenger aircraft that could use significantly less fuel?

Yes, please!

But the Transonic Truss-Braced Wing aircraft, or TTBW, the concept design shown here inside a NASA wind tunnel, is quite a departure from “business as usual.” So, plenty of exploratory testing is a must to predict how it will perform in flight.

This scale model represents only half the aircraft to allow the tunnel to hold a bigger model. That way, it can be packed with hundreds of sensors embedded all over its surface to measure different factors, including pressure forces, when the air starts flowing.

That was necessary for a test recently completed in the Unitary Plan Wind Tunnel at NASA’s Ames Research Center in California’s Silicon Valley. It was looking at buffet, a type of vibration that can affect aircraft flying at high speeds. Buffet is caused by the rapidly changing pressure forces of air flowing unsteadily over the wings.

The TTBW’s extra-long, thin wings stabilized by diagonal struts should make it lighter than a traditional airliner, and their shape will create less drag in the air. The plane will burn less fuel – likely an extra 8-10 percent less than aircraft with similarly advanced technologies but a traditional wing design.

The researchers designing the TTBW, a collaboration between NASA and Boeing, will use the data from the recent test to find the upper limits the aircraft can perform at – in terms of combinations of factors like speed and altitude – before the vibrations caused by buffet become excessive.

This will help them better understand how their plane will really fly and how well their tools are predicting the vehicle’s performance. Where computer simulations may be less accurate capturing certain effects, like buffet, wind tunnel tests can clarify how well they’re predicting the flow of air over this unusual truss-braced configuration.

If any gaps are identified in the predictions, the TTBW team will continue studying them. And that will give its designers every confidence in their aircraft when it takes off for its first fuel-efficient flights. If successful, this technology could potentially be used for new aircraft in the 2030s.

The TTBW concept is part of an ongoing initiative by NASA, industry partners, and academia to make the future of aviation more environmentally friendly through the Sustainable Flight National Partnership.

Image caption: A model of the Transonic Truss-Braced Wing aircraft is seen here installed for testing in the Unitary Plan Wind Tunnel at NASA’s Ames Research Center in California. A model representing just half the airplane, sliced from nose to tail, is used so that the tunnel can fit a larger-scale model holding hundreds of sensors to record data during the test. At about 11 feet long and 7.5 feet from floor to wing tip, this model is 9 percent of the size of the full-scale aircraft.

Author: Abby Tabor, NASA’s Ames Research Center