Researchers at the Massachusetts Institute of Technology (MIT) have unveiled designs for two new aircraft which they say could usher in a cleaner and quieter era of civil aviation.

The designs dubbed "double bubble" and the "hybrid wing body" could reduce fuel consumption by up to 70 percent as well as limiting nitrogen oxide (NOx) emissions by 75 percent compared with existing commercial aircraft, MIT researchers say.

MIT's concepts were presented to NASA in April as part of a $2.1 million research contract exploring ways of improving aircraft efficiency in the future.

The "D 'double bubble' series" has been designed as a potential successor to Boeing's short to medium range 737, while the "H 'hybrid wing body' series" is seen as an eventual replacement for Boeing's 300-passenger 777.

MIT have rejigged the traditional tube-and-wing structure for the "D series." Instead of using one fuselage cylinder they have forged two together, placing them side by side.

The engines traditionally attached to the wings are redeployed at the rear of the plane and use a propulsion system called Boundary Layer Ingestion (BLI).

On traditional commercial aircraft, engines located on the wings take in an undisturbed, fast-flowing air stream. But with the BLI system, the engines take in slower moving air created in the wake of the fuselage, allowing aircraft to use less fuel and reduce noise.

There are drawbacks, say MIT, notably increased engine stress. But Mark Drela, professor of fluid dynamics at MIT and lead designer of the "D Series," says this could be mitigated by traveling at slightly slower speeds than a traditional Boeing 737.

Along with the considerable fuel savings and noise reduction, the major advantage of the "D series," according to Drela, is that it looks much like a conventional airplane.

"It would fit existing infrastructure at airports, so all the ground-based equipment would look the same," Drela told CNN.

MIT have devised two versions of the "D series." One model," Drela says, "has been intentionally simplified for current technology, using aluminum so it can be built like a conventional airline."

The other model, he says, involves "hi-tech composite materials and engines that don't quite exist yet, but are forecast."

The more ambitious "H 'hybrid wing body' series" uses similar technology to the "D series" but also explores the idea of having multiple smaller engines.

Its radical triangular-shape which blends wing and fuselage make it lighter and more aerodynamic than conventional aircraft, but Drela concedes that for the "H series" to be a commercial reality all existing airports would require a redesign.

With phase one now complete, Drela hopes the concepts can be taken to the next level, which means testing scale models in wind tunnels and collaborating with aircraft manufacturers to explore ways of making the designs a reality.

CNN