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NASA's New X-Plane Design Has 18 Engines, Pencils for Wings

But it boasts the lift-to-drag ratio of an albatross.
March 22, 2015, 7:49pm

​Ever catch yourself sitting at 30,000 or so feet crammed knee to seatback in some metallic tube of an Airbus with 200 other humans gazing out the window at those thin airliner wings, thinking,"no, this isn't right?" It's not right at all even: a whole movie theater load of people and baggage and cans of soda and tens of thousands of gallons of jet fuel all floating along like it's nothing. Physics is great, but modern air travel is still no match for ground-based intuition. It just looks wrong, like magic.

NASA's newest X-Plane design, the latest in the agency's ​long line of "x" designated experimental aircraft, makes even the most extreme commercial airliner look like a balsa wood glider in comparison. The LEAPTech, as the craft is known, sports a wing area of about 55 square feet, which is roughly a third that of its nearest comparison, the Cirrus SR22, the best selling single-engine composite aircraft on the market.

The point of the LEAPTech craft is mostly to enhance takeoff and landing efficiencies, which it achieves thanks to a sharply limited stall speed. This allows takeoff and landing speeds of just 61 knots, or about 70 miles per hour. Meanwhile, the LEAPTech design boasts a lift-to-drag ratio of 22, ​compared to the 11 achieved by the SR22 design. So, it's more in line with the U2 spy aircraft (28), a 747 (17), or an albatross (20).

Image: NASA/Joby Aviation

The LEAPTech craft's weapon is what's known as a blown wing. Most aircraft achieve lift via massive amounts of thrust provided by one or a few engines. The plane is pushed through the air and the air moving around the wing provides lift. A blown wing instead offers an array of relatively small fans/propellers, which blow air directly onto the wing in just the right way as to provide lift. It's sort of like skipping the aeronautic middleman. The propellers are able to run on electricity, which is part of the point.

"Electric propulsion possesses the potential to create a much greater paradigm shift in aircraft design than might be initially apparent," ​a NASA concept paper explains. "While directly replacing combustion engines with electric motors can impart benefits of simplicity, reliability, low noise, and low maintenance, far greater benefits may be realized by taking advantage of the unique properties of electric propulsion through configurations that have been impractical or impossible [otherwise]."

The first LEAPTech experimental demonstrator arrived at NASA's Armstrong Flight Research Center on February 26. So far it's basically just a wing strapped to the back of a truck. The next stage, to be reached within the next couple of years, is to actually build a LEAPTech X-plane. The near-term target is a general aviation-ready version, but there's nothing fundamental to preclude the technology's expansion to larger jets.

As NASA ​aerodynamicist Mark Moore notes, "LEAPTech has the potential to achieve transformational capabilities in the near-term for general aviation aircraft, as well as for transport aircraft in the longer-term."

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