When the airline industry agreed to the first-ever carbon emissions limits for planes in February, they didn't go very far. By 2028, the proposed rules would only make new planes cut fuel use by 4%-11% compared to a plane made in 2015. A suite of new technologies tested at NASA show some of the ways that airlines could do much more—if the technology can feasibly come to market.
For the last six years, NASA has tested several different technologies that can cut fuel use by 50%. The new designs are part of the agency's Environmentally Responsible Aviation project, which also tested features that could reduce airplane noise to an eighth of current levels and cut pollution that causes local smog by as much as 80%.
To save fuel, the new designs tackle three problems—the weight of the plane, how much drag holds it back, and how much the engine guzzles fuel. Every detail matters. On a plane with wings designed to be more aerodynamic, something as simple as insect guts on the wing can increase drag. The researchers tested new coatings—inspired by self-cleaning lotus leaves—that can keep insects off.
Another technology uses tiny nozzles to blow air over the tail of the plane; by controlling airflow, the tail can be smaller, making the plane lighter. "You weigh less, you're going to burn less fuel," says Fayette Collier, ERA project manager. The project also looked at new lightweight materials and took inspiration from car manufacturers to design a new way to make planes out of a single body, reducing weight even more. "We think we can save about 20% structural weight with this idea," he says. "That adds up to be a big contribution."
In the engine, the team tested two new technologies that make jet engines much more efficient. Taken together, all of these technologies—cutting weight, drag, and fuel—can trim jet fuel use in half compared to today's levels. "What we're trying to do here is fill the technology pipeline with technologies that could be used to achieve these goals simultaneously," says Collier.
The catch: They're not quite ready yet. NASA typically helps develop technology only part of the way. On a "maturation scale" of 1 to 9, where something rated 9 is ready for market, NASA works on technology until it's about a 6. Then it's up to the private industry to take it farther.
"Some of that depends on timing—whether or not they have a new product coming out, and whether or not this technology fits into that product," says Collier. "Typically the time for industry to mature it is five or six years, but it can be longer. It depends on market demands and the products available."
Even if the airline industry does eventually develop and adopt every single fuel-saving technology from the NASA project, that also still won't be enough for the industry to meet its longer-term goal: By 2050, the industry hopes to slash net emissions by 50% compared to 2005 levels.
"I ask myself every day, how are we going to do this," says Collier. "The trick is, demand is growing as well. You have increasing demand for air travel, so there's probably going to be more airplanes." That’s especially true in the developing world, where air travel is growing 7%-8% a year; in the developed world, it's expected to increase about 2% a year. It won't take long for gains from more efficient planes to be overtaken by the fact that so many more people are flying.
"With technologies in the pipeline, we think we're about halfway there," he says. "So we've a long way to go, there's a lot of work left to be done, to get the rest of it. What we're looking at is even an additional sweep of technology to start working on, as well as alternative low-carbon fuels."
A study last year was optimistic about what it will take to make the transition. Researchers calculated that by taking a variety of steps—not just using new technology and fuel, but replacing the oldest planes early and flying fewer half-empty planes—it would be possible to cut emissions in half without costing airlines anything extra. (This only works if oil costs more than $50 a barrel, which is not the case right now).
Even without NASA's cutting-edge developments, it wouldn't take much for most airlines to dramatically increase efficiency. Just by using newer planes, the Airbus 320, Virgin America's flights are as much as 15% more efficient than other domestic carriers. In 2017, the airline plans to start using some even newer planes (the Airbus A321neo) which are as much as 20% more carbon efficient than their current fleet. There's no reason other airlines can't follow.