MIT Designs Eco-friendly Aircraft with a 70% Fuel Burn Reduction

MIT has delivered designs of two ultra-efficient green plane models to NASA, as part of a $2.1 million research contract awarded in 2008.
The aircraft feature a different silhouette than to current day models and will offer a 70% fuel burn reduction.
The D Series is expected to replace the 737 while the H Series is expected to replace the 777.
The NASA requirements demanded a 70% fuel burn reduction, a 75% emissions reduction and the ability to take off from shorter runways.

D Series

The D Series will carry around 180 passengers and features rear-mounted engines. The aircraft uses two partial cylinders placed side by side to create a wider structure instead of using a single fuselage cylinder.
MIT believes that the rear mounted engines will intake slower moving air thus reducing the fuel burn ( known as Boundary Layer Ingestion , however also notes that this has some practical drawbacks such as creating more engine stress . However, they expect to mitigate this drawback by travelling around 10% slower than a 737. It is also worth noting that rear-mounted engine are practically hard to maintain too .
The aircraft features thinner wings and a smaller tail to reduce drag.
Mark Drela, the Terry L. Kohler professor of Fluid Dynamics and the lead designer of the D Series believes that the 10% slowness could be recovered by the faster loading and the ability to take off from airports with short runways.
MIT team has designed two versions of the D Series – a higher technology version with 70% fuel burn reduction and a version that could be built with conventional aluminium and current jet technology that would burn 50% less fuel. They expect the latter to be a lower risk, near-term alternative.

H Series

The H Series is expected to carry around 350 passengers and consists of a triangular shaped hybrid wing body.
This type of design has been proposed a multiple times in the past too, in both military and commercial projects. The hybrid wing body blends a wider fuselage with the wings for improved aerodynamics. The large center body creates a forward lift that eliminates the need for a tail to balance the aircraft. Although the H Series currently meets the NASA goals, the researchers expect to further improve the design to meet more objectives.
The MIT team expects to hear from NASA in the next several months about whether it has been selected for the second part of the program, which will provide more funds to one or two of subsonic teams to develop the technologies identified during the first phase. The teams are part of a competition by NASA, in which six U.S teams won contracts. The teams include four teams led by MIT, Boeing, GE Aviation and Northrop Grumman which studied subsonic ( slower than speed of sound ) aircraft and two more teams led by Boeing and Lockheed-Martin which studies supersonic ( faster than speed of sound ) aircraft concepts. NASA identifies these designs as “N+3″, signifying three generations ahead than current designs, and believes advancement of technologies will make it feasible for these designs to fly by around 2035.

However, it remains to see whether these aircraft will be economically viable to build and it is also not clear which are the radical technological improvements used, other than aerodynamics and possibly engine technologies, to achieve a 70% fuel burn reduction. Let’s hope these designs will become a reality and deliver what they promise.