For the last few years, NASA’s “bug team” has been shooting insects at 150 miles per hour towards stand-in airplane wings. But the tiny test subjects do not die in vain. NASA is attempting to developing a non-stick coating to hopefully reduce the bug gut load on airplane wings, which gets more serious than you’d expect. This week scientists finally flew with their created coatings.
Hitting one bug during a flight is insignificant. Hitting millions over thousands of hours of flight time is a real problem. Carefully engineered airplane wings build up bug gut gunk, which interferes with the aerodynamics, in turn noticeably reducing fuel efficiency. To get guts slipping off the wings, the bug team developed over 200 coatings, each tested in a wind tunnel. That was 2013.
Then, about a month ago, NASA announced that they would be testing five of those coatings on real airplane wings, with 15 flights taking off and landing from the Shreveport Regional Airport in Louisiana.
This week, NASA finally conducted those flights using Boeing’s ecoDemonstrator 757. “Shreveport was chosen in part because of its significant bug population,” according to NASA’s press release. In other words, there’s a lot of bugs in Louisiana. Still, pilots had to “work around storms and winds to ensure the bugs would be present en masse.”
The problem with bug guts, as opposed to water or other air participates, is that they are sticky. When a bug smashes against an airplane’s wing, its blood and bodily fluids contact the air and coagulate. “We learned when a bug hits and its body ruptures the blood starts undergoing some chemical changes to make it stickier,” says Mia Siochi, senior materials scientist at NASA’s Langley Research Center in Hampton, Virginia.
“That’s basically the survival mechanism for the bug.”
To get around this, NASA scientists turned to nature for inspiration. The coatings they came up with mimicked something already famous for repelling liquid: the leaves of the lotus flower. To our eyes, these leaves look pretty normal, if not a bit hairy. But upon closer inspection, the surfaces of the leaves are covered with millions of tiny hair-like structures. They are so close together that the structures actually suspend liquid droplets, like a bed of nails that can support but not pop a balloon.
It makes water look like the remnants of a shattered T-1000:
The best performing coatings effectively did the same to bug guts in flight, reducing airplane wing splatter counts by up to 40 percent (compared to control surfaces).
But slipperiness is just one feature these coatings need to have. Splattering bugs only cuts into efficiency after many hours of flight time. A final coating would need to have the longevity to last through sustained bug barrages, inclement weather, and natural erosion. NASA will need more bug gun.
IMAGES: NASA/Paul Bagby; NASA Langley / David C. Bowman