Al Bowers is the program manager of Preliminary Research Aerodynamic Design to Lower Drag, or Prandtl-d. The project’s researchers validated elements of a boomerang-shaped wing design that could greatly improve the efficiency of future aircraft.
NASA Tech Briefs: Your wing is inspired by German engineer Ludwig Prandtl from the 1930s. What is Prandtl’s proposed wing design?
Al Bowers: The wing is flat at the center, and then it tapers to the tip and flattens out; the curve is absolutely flat when it gets to the wing tip. The shape of the curve looks very bell-shaped. The bell-shaped span load pushes the air down in the center. But in the wing tips, the flow goes up, and you have upwash at the wing tips. The lift vector is rotated forward at the tips. If you increase the lift on one side, you roll correctly and you yaw correctly at the same time. This is what birds have been doing naturally. That’s exactly what the load needs to be.
NTB: What is possible now, and why is this wing shape important?
Bowers: When Prandtl first published his result, he got 11 percent less drag than the elliptical span load for the same amount of structure. Right off the bat, the wing is 11 percent more efficient. You can also get rid of the vertical tail, and all that weight, drag, and complexity; you’re doing everything with the wing alone. This impacts carbon footprint and range. This makes electric propulsion more possible.
NTB: How did you validate this wing design?
Bowers:. We made a 12-and-a-half-foot-span glider, and we put instrumentation on there to measure the roll and the yaw. We’re building a bigger, 25-foot-span glider with pressure in the wing and a fiber optic load system. All of this work has been done with student intern labor. I had friends at Langley Research Center who have access to a great wind tunnel. We got 52 wind tunnel runs and about 6,000 data points
NTB: How can this wing be used on a Mars airplane?
Bowers: When the Curiosity rover went to Mars three years ago, JPL had to carry 57 kilograms of ballast onboard the aeroshell in order to spin-stabilize the spacecraft during the cruise portion to Mars. When they got to Mars, they ejected that ballast. They landed on Mars, and that rover has been sending great science back ever since. I’d love to be a couple of kilograms of that ballast going to Mars.
You have this incredibly simple integrated solution that doesn’t require all sorts of complexity in order to make it stable and controllable. Now imagine that you could take one of these aircraft and make it really small, out of a material that you can roll up and fit into a really small container. We’re trying to fit it into a CubeSat if we can get away with it.
If we could find a way to enter the Martian atmosphere, and while we’re still hanging under the parachute at maybe 15,000 feet or 12,000 feet about the surface, just jettison this little, rolled-up airplane that we suddenly spring out, you could put really simple science experiments on there. You could get the profile of the atmosphere of Mars right down to the surface.
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