Washington: In what could revolutionize the aviation industry, a 'green airplane' designed by a Massachusetts Institute of Technology (MIT)-led research team is likely to use 70 percent less fuel than existing ones while slashing noise and emission of nitrogen oxides.

The design was one of two that the team, led by faculty from the MIT Department of Aeronautics and Astronautics (AeroAstro), presented to NASA last month as part of a $2.1 million research contract.

MIT was the only university to lead one of the six US teams that won contracts from NASA in October 2008. Ed Greitzer, professor of aeronautics and astronautics was the principal investigator of the project.

Known as "N+3" to denote three generations beyond today's commercial fleet, the 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.

The team's objective was to develop concepts for, and evaluate the potential of, quieter subsonic commercial planes that would burn 70 percent less fuel and emit 75 percent less nitrogen oxides than today's commercial planes.

NASA also wanted an aircraft that could take off from shorter runways. Designing an airplane that could meet NASA's aggressive criteria while accounting for the changes in air travel in 2035 -- when air traffic is expected to double -- required "a radical change", according to Greitzer.

The MIT team met NASA's challenge by developing 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-and-wing 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, said an MIT release. IANS