Boeing builds bracing-wing aircraft, increasing efficiency by 30%
Boeing will construct and test a full-size aircraft based on the supersonic bracing wing (TTBW) idea, which employs long, thin, strut-tipped wings to lift more, cut drag, and burn 30% less downforce, with $425 billion in funding from NASA.
A one-digit improvement in fuel efficiency can save a lot of money when you use as much gasoline as an aircraft. Consider the aeroshark film that Swiss Airlines has applied to 12 of its Boeing 777s. It improves performance by 1%, allowing Swiss to utilize fewer aircraft overall with just 12 in service. 4,800 tons of jet fuel annually, saving each aircraft at the current price over half a million dollars annually. For a company like American Airlines, which closes with 1,000 aircraft in its fleet, that would be around $500,000,000 per year from a 1% performance boost.
You can see how an airplane that is 30% more efficient than the top single-aisle vehicles now in use may be somewhat of a significant deal. In 2010, as part of the “Subsonic Ultra Green Aircraft Research” (SUGAR) Volt idea it developed as part of a NASA research program, Boeing introduced its “truss-braced wing” design concept.
The concept makes use of longer, smaller, high aspect ratio wings, such as those of an unpowered glider, which provide higher lift and reduced drag. For instance, a prototype Boeing tested in 2016 had wings that were roughly 50% broader than those of equivalent regular aircraft.
That sort of thing simply doesn’t function structurally without reinforcement. Thus, the Boeing design suspends the wings from the top of the fuselage and braces them with protruding long trusses from the plane’s belly. They are also precisely designed airfoils that provide additional lift in addition to strength and stability.
Boeing estimated that these braced-wing airliners might burn 50% less fuel than a typical aircraft while cruising at Mach 0.70 to 0.75 (519 to 556 mph, 835 to 895 kph). The concept was revised in 2019 to cruise at Mach 0.8 (593 mph, 955 kph), which is on the verge of transonic speed. Whether as a result of the increased speed or simply from a better understanding of aerodynamics, Boeing has increased efficiency.
According to a press release from Boeing, a single-aisle airplane with a TTBW configuration “coмined with expected adanceмents in propulsion systeмs, мaterials and systeмs architecture” could reduce fuel consumption and emissions by up to 30% compared to today’s most efficient single-aisle airplanes, depending on the mission.
After years of digital modeling and small-scale wind tunnel testing, NASA has now granted Boeing funding under the SFD Space Act agreement in the amount of $425 million, which will be combined with another $725 million from Boeing and other business partners to go ahead and build the thing at full scale and conduct the necessary flight tests.
Transonic Truss-Braced Wing demonstrator aircraft testing will be finished by NASA “by the late 2020s, so that technologies and designs demonstrated by the project can inform industry decisions about the next generation of single-aisle aircraft that could enter service in the 2030s,” according to NASA.
There will undoubtedly be difficulties. To begin with, these extraordinarily long wings might just not fit in hangars or airport terminals that are already in use. About the demonstrator aircraft, Boeing hasn’t revealed anything, but on the 2019 design, it mentioned employing foldable wings to circumvent this problem on the ground.
And then there’s the fact that the typical airliners’ enormous, thick, lower aspect ratio wings perfectly hollow out a place for their fuel tanks. By keeping the fuel out in the wings, the stress on the engineering where the wings meet the body is reduced because there is a lot of weight out wide, closer to the center of lift. By keeping burning fuel away from the passengers in a crash, it considerably increases safety. And from a purely practical standpoint, it makes room in the cabin for additional lucrative seats. Fuel tanks will probably need to be moved back into the fuselage because the truss-braced design has such thin wings.
While this demonstration won’t be testing any fancy new engines right away, Boeing claims that the high-mounted, braced wings “may someday support sophisticated propulsion systems that are constrained by a lack of underwing room in today’s low-wing airplane layouts.”
And it should go without saying that anything that can let airplanes fly farther on a given amount of energy is especially relevant to attempts to reduce carbon emissions. These designs might undoubtedly make a significant contribution because clean powertrain options such as battery-electric, hydrogen-electric, hydrogen-coмbustion, ammonia, and others are all hampered by lower range statistics than conventional jet fuel power.
The video below shows some of the CFD (Computational Fluid Dynamics) and wind tunnel work that went into this design, including a fairly gnarly-looking flutter simulation that gives us the impression that trains would be a pretty decent alternative.
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