A recently sold item on EBay was this piece of artwork depicting a Boeing concept for an airliner powered by two propfans. These engines, popular items of study in the late 70s and into the 80s, were somewhere between turbofans and turboprops, with contra-rotating unducted fans using blades of complex design and contours. The advantage was, of course, fuel efficiency; the shape of the blades meant that they could spin with tip speeds closer to the speed of sound compared to turboprop blades, and could push the plane faster than normally practical for a turboprop.
Given the NASA logo on the tail, this piece of art undoubtedly depicts a proposal for an unducted fan test vehicle. The gray areas on the wing upper surfaces may indicate laminar flow control via suction, as with the Northrop X-21; this would all conspire to make this a very fuel efficient, if also very complex, jetliner.
