This chubby fellow is MIT's "double-bubble" concept aircraft, designed for super efficient passenger travel a couple decades from now. Along with other ideas (like Boeing's SUGAR Freeze), NASA is betting that jets like these will revolutionize commercial air travel.
Not content to leave innovation up to the aerospace industry alone, NASA has been taking some initiative by helping companies and academic institutions develop aircraft of the future, contributing funds, expertise, wind tunnel time, and oh yes, funds.
This particular project, the "Double-Bubble," uses a variety of tricks to dramatically slash fuel consumption. For starters, it's fat, and that wide fuselage contributes enough lift to the aircraft as a whole that it can utilize a lighter, thinner, and lower sweep wing. Being so fat also allows it to carry the equivalent of two passenger cabins (which is where the double-bubble bit comes from), meaning that the fuel per passenger is substantially decreased as well. And finally, shoving the engines back by the tails helps them to operate more efficiently, while simultaneously decreasing drag on the aircraft as a whole by pumping exhaust out into the wake turbulence.
As a whole, the double-bubble concept should save on fuel by about 70% compared to today's aircraft, but the interesting thing is that a full 50% of this efficiency boost comes from the design changes and not from fancier engines or a lighter fuselage or anything like that. So really, by building a plane like this even now, we'd realize a huge amount of fuel savings.
Such a drastic new aircraft is probably not realistic in the short-term, but NASA will allow MIT to test out a 1/4 scale powered model this concept in a subsonic wind tunnel, where its performance can be directly compared to the 737-800, which is sort of the standard of the current generation passenger aircraft. The Double-Bubble is what's called an N+3, or three generations from now, meaning that you might be flying on one in 2035 or so.
Via Aviation Week