In what could set the stage for a fundamental shift in commercial aviation, a Massachusetts Institute of Technology (MIT) – led team has designed a green aircraft that is estimated to use 70 per cent less fuel than current planes while also reducing noise and emission of nitrogen oxides (NOx).

The design was one of two that the team, led by faculty from the Department of Aeronautics and Astronautics, presented to NASA last month as part of a US$2.1 million research contract to develop environmental and performance concepts that will help guide the agency’s aeronautics research over the next 25 years. Known as “N+3” to denote three generations beyond today’s commercial transport fleet, the research programme is aimed at identifying key technologies, such as advanced airframe configurations and propulsion systems, that will enable greener airplanes to take flight around 2035.

Four teams — led by MIT, Boeing, GE Aviation and Northrop Grumman, respectively — studied concepts for subsonic commercial planes, while teams led by Boeing and Lockheed- Martin studied concepts for supersonic commercial aircraft. Led by AeroAstro faculty and students, the MIT team members include Aurora Flight Sciences Corporation and Pratt & Whitney.

The team noted that while automobiles have undergone extensive design changes over the last half-century, “aircraft silhouettes have basically remained the same over the past 50 years, based on the traditional “tube-and-wing” structure of an aircraft’s wings and fuselage.

The MIT team developed two designs: The 180-passenger D “double bubble” series to replace the Boeing 737 class aircraft, currently used for domestic flights, and the 350 passenger H “hybrid wing body” series to replace the 777 class aircraft now used for international flights.

The engineers conceived of the D series by reconfiguring the tube-andwing structure. Instead of using a single fuselage cylinder, they used two partial cylinders placed side by side to create a wider structure whose cross-section resembles two soap bubbles joined together. They also moved the engines from the usual wing-mounted locations to the rear of the fuselage. Unlike the engines on most transport aircraft that take in the high-speed, undisturbed air flow, the D-series engines take in slower moving air that is present in the wake of the fuselage. Known as the Boundary Layer Ingestion (BLI), this technique allows the engines to use less fuel for the same amount of thrust, although the design has several practical drawbacks, such as creating more engine stress.

Over the next several months NASA will select a design for the second phase of the programme, which will provide additional funds to one or two of the subsonic teams in 2011 to research and develop the technologies identified during the first phase.