As much as we complain about air travel, the fact is, flying has gotten considerably cheaper, safer, faster, and even greener, over the last 60 years.
Today's aircraft use roughly 80 percent less fuel per passenger-mile than the first jets of the 1950s – a testimony to the tremendous impact of aerospace engineering on flight. This increased efficiency has extended global commerce to the point where it is now economically viable to ship everything from flowers to Florida manatees across the globe.
In spite of continuous improvements in fuel-burning efficiency, global emissions are still expected to increase over the next two decades due to a doubling in air traffic, so making even small improvements to aircrafts' fuel efficiency can have a large effect on economies and on the environment.
This potential for impact motivates Joaquim Martins, an aerospace engineer at the University of Michigan (UM) who leads the Multidisciplinary Design Optimization Laboratory, to develop tools that let engineers design more efficient aircraft.
"Transportation is the backbone of our economy. Any difference you can make in fuel burn, even a fraction of a percent, makes a big difference in the world," Martins says. "Our goals are two-fold: to make air transportation more economically feasible and at the same time to reduce the impact on the environment."
Using the Stampede supercomputer at the Texas Advanced Computing Center, as well as computing systems at NASA and UM, Martins has developed improved wing designs capable of burning less fuel, as well as tools that help the aerospace industry build more efficient aircraft.
"We're bridging the gap between an academic exercise and a practical method for industry, who will come up with future designs," he says.
Improvements in wing design have the potential to improve efficiency up to 10 percent, lowering costs and pollution. Moreover, in areas where new technologies are being applied, such as for wings made of composite materials or wings that morph during flight, improved design tools can provide insights when intuitive understanding is lacking.
Today's airplanes feature 50 percent composites materials, but the composites are placed in a relatively simple way. New automatic fiber placement machines, however, can place composites in complex curves, creating what are known as tow-steered composite wings.
"That opens up the design space, but designers aren't used to this," Martins says. "It's challenging because there isn't a lot of intuition on how to utilize the full potential of this technology. We developed the algorithms for optimizing these tow-angles."
He found that tow-steered composites can reduce the structural weight of an aircraft by 10 percent when compared to conventional composite designs while reducing the fuel burn by 0.4 percent. NASA is in the process of building a prototype of a tow-steered wing box for a scale test at NASA's Armstrong Flight Research Center.
Another area of study is morphing wings that change shape to maintain maximal performance regardless of flight speed, altitude, and aircraft weight. Martins, David Burdette, and Gaetan Kenway (all from UM) have presented results for a morphing design that has the potential to burn 2 percent less fuel than current designs.
A third area of investigation involves new high-aspect ratio wings that have a much larger span than those in use today. Martins has presented designs for such a wing. Boeing has adapted that model and will build a prototype to test at NASA Langley Research Center's Transonic Dynamics Tunnel.