NASA and Boeing this week showed off new technology that could go a long way toward reducing the size, weight and drag of future, greener aircraft.
NASA and Boeing said they recently completed tests of technology they call Active Flow Control, which places small, computer controlled devices known as actuators on the surface of a wing that then blow air in a sweeping motion along the span of the aircraft's surface.
As these actuators blow air over the surface, they help to redirect and reattach the air flow that would otherwise be separated causing drag, at some of the higher rudder angles. Eliminating such air flow separation on the surface benefits performance but also could enable the design of simpler, smaller and more aerodynamically efficient structures that help reduce aircraft weight, drag, and fuel consumption, NASA stated.
To prove the technology works, NASA and Boeing tested Active Flow Control on a full size Boeing 757 vertical tail in the U.S. Air Force's Arnold Engineering Development Center's 40- by 80-foot wind tunnel at Ames in Moffett Field, Calif.
The wind tunnel tests enabled the Boeing and NASA team to observe "a wide array of flow control configurations across the whole low-speed flight envelope of the vertical tail," said Ed Whalen, Boeing Research & Technology program manager for the testing in a statement. The team will pick the most efficient and effective flow control configuration for future flight testing "to see how it performs in the real flight environment."
The combined wind tunnel and flight tests represent the first full-scale flight demonstration of this active flow control technology, Whalen said. "That will give us insight into how the system works, how effective and efficient it is, things that we're not completely sure of at this point."
"The maturation of technologies such as active flow control, which will benefit aviation by improving fuel efficiency, reducing emissions and noise levels, is what NASA's aeronautics research is all about. The promising results of these wind tunnel tests and the following flight demonstration in 2015 undoubtedly will have an impact on future "green" aircraft designs," added project manager Fay Collier.
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The test is part of NASA's ongoing Environmentally Responsible Aviation (ERA) Project that is looking "the feasibility, benefits and technical risk of vehicle concepts and enabling technologies to reduce aviation's impact on the environment."
ERA has some lofty goals. For example by 2025 it expects to develop systems that:
- Reduce aircraft drag by 8%
- Reduce aircraft weight by 10%
- Reduce engine specific fuel consumption by 15%
- Reduce oxides of nitrogen emissions of the engine by 75%
- Reduce aircraft noise by 1/8 compared with current standards.
NASA, Boeing and others have been developing greener aircraft for the future. In 2011 NASA awarded $16.5 million to Boeing, Northrop Grumman, MIT, Cessna to continue developing quieter, cleaner, and more fuel-efficient jets. At the time NASA said the money was awarded after an 18-month study of all manner of advanced technologies from alloys, ceramic or fiber composites, carbon nanotube and fiber optic cabling to self-healing skin, hybrid electric engines, folding wings, double fuselages and virtual reality windows to come up with a series of aircraft designs that could end up taking you on a business trip by about 2030.
The projects look like this:
The Boeing Company's Subsonic Ultra Green Aircraft Research, or SUGAR is a twin-engine aircraft with hybrid propulsion technology, a tube-shaped body and a truss-braced wing mounted to the top. Compared to the typical wing used today, the SUGAR Volt wing is longer from tip to tip, shorter from leading edge to trailing edge, and has less sweep. It also may include hinges to fold the wings while parked close together at airport gates. Projected advances in battery technology enable a unique, hybrid turbo-electric propulsion system. The aircraft's engines could use both fuel to burn in the engine's core, and electricity to turn the turbofan when the core is powered down ($8.8 million)
MIT's 180-passenger D8 "double bubble" fuses two aircraft bodies together lengthwise and mounts three turbofan jet engines on the tail. Important components of the MIT concept are the use of composite materials for lower weight and turbofan engines with an ultra high bypass ratio (meaning air flow through the core of the engine is even smaller, while air flow through the duct surrounding the core is substantially larger, than in a conventional engine) for more efficient thrust. In a reversal of current design trends the MIT concept increases the bypass ratio by minimizing expansion of the overall diameter of the engine and shrinking the diameter of the jet exhaust instead ($4.6 million).
Northrop Grumman will test models of the leading edge of a jet's wing. If engineers can design a smooth edge without the current standard slats, airplanes would be quieter and consume less fuel at cruise altitudes because of the smoother flow of air over the wings ($1.2 million).
Cessna will focus on airplane structure, particularly the aircraft outer covering. Engineers are trying to develop what some call a "magic skin" that can protect planes against lightning, electromagnetic interference, extreme temperatures and object impacts. The skin would heal itself if punctured or torn and help insulate the cabin from noise, NASA says ($1.9 million).
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