While SUGAR Volt may sound like the name of an energy drink, or maybe an all-girl J-Rock band, it is actually a Boeing concept for an airliner of the future. SUGAR stands for Subsonic Ultra Green Aircraft Research, a NASA-organized project, and the Volt is related to the concept’s hybrid-electric propulsion. The goal of SUGAR is to look ahead to 2030-2035 to an N+3 design – which means three generations beyond today’s aircraft. The two leading designs from Boeing are SUGAR Volt and SUGAR High, which is basically the same airframe but with a more conventional power system. For SUGAR High the combination of airframe and propulsion improvements, along with improvements to air traffic control, could result in a 44% to 58% reduction in fuel burn. While the SUGAR High concept could boost that beyond 70%.
The new design looks a bit different from today’s airliners. It is still a tube-and-wing design, but the wing is high-mounted and has a very high aspect ratio – it is very long and thin. Because it is so long and thin it is also strut-braced – something you really only see today on high-wing light aircraft and a handful of smaller transport aircraft. Using struts allows you to avoid beefing up the primary structure to carry its own load, which can add a great deal of weight. It is a trade off between the added aerodynamic drag and structural complexity of the strut vs. the added weight of a pure cantilever design. And some designs may not be feasible without the added support of a strut.
Another unique feature is that the wing is designed to fold to allow the use of today’s airport gates. That may sounds a bit crazy, but it isn’t the first time Boeing has designed such a thing. The B777 was originally designed with the option for folding outer wing panels to allow it to use the same gate spacing as the smaller B767. This was done mainly for American Airlines – who then went on to not order the B777 for a while, and when they did never opted for the folding wings. But Boeing designed, tested, and certified a wing fold mechanism for the B777, so they have experience doing this for a commercial aircraft.
While they first unveiled the SUGAR Volt concept back in 2010, they’ve continued to refine it and just published the following video to YouTube:
Personally I really like Boeing’s more recent SUGAR Freeze concept, an N+4 concept for the 2045 timeframe. It evolves the SUGAR High & SUGAR Volt concepts by utilizing liquefied natural gas (LNG) and fuel cells to generate power. In either case, LNG is a cheaper & cleaner alternative to Jet-A, but it adds the complexity of needing to be stored cryogenically under high pressure.
I’m still partial to the blended wing body concepts myself, just because they are so radically different from today’s wing-and-tube designs. But I know in the end there are many factors that will determine future designs – materials, propulsion, aerodynamics, maintenance, ground handling, passenger preferences, etc.