NASA tests air­craft bug- sloughers

Non­stick coat­ings for air­plane wings can keep in­sect guts from be­ing a lit­eral drag.

Los Angeles Times - - THE NATION - By Ta­mara Di­et­rich tdi­et­rich@dai­ly­

HAMP­TON, Va. — Who knew that keep­ing bug guts off air­planes could be a mis­sion for NASA?

It turns out that in­sect “residue” splat­ter­ing on the wings of big air­craft as they take off is a real prob­lem look­ing for a se­ri­ous so­lu­tion.

“They are re­ally small,” con­ceded Christo­pher Wohl, se­nior re­search ma­te­ri­als engi­neer at NASA Langley Re­search Cen­ter in Hamp­ton. “But the prob­lem is that, as these residues ac­cu­mu­late on the wing, they can im­pact the airf low.”

And any­thing that af­fects airf low adds to a plane’s drag, de­creas­ing ef­fi­ciency and in­creas­ing fuel use and costs.

So about f ive years ago, Wohl and his team be­gan to look into lit­er­ally hun­dreds of non­stick coat­ings for air­plane wings that could best slough off bug guts. They nar­rowed it down to the top five po­ten­tials and put them through a se­ries of f lights on Boe­ing’s ecoDe­mon­stra­tor 757 test air­plane.

Pre­lim­i­nary re­sults in­di­cate the coat­ings can do the job just fine, po­ten­tially sav­ing the air­line in­dus­try a bun­dle in cu­mu­la­tive fuel costs.

“Sav­ings can be rel­a­tively small when you talk about fuel sav­ings as far as per­cent­age- wise — like half a per­cent,” Wohl said. “But the im­pact of that across the en­tire avi­a­tion in­dus­try can be re­ally enor­mous.”

In fact, he said, the most promis­ing coat­ing man­aged to re­duce bug residue by 40% com­pared with con­trol sur­faces. He es­ti­mated the po­ten­tial an­nual sav­ings to air­lines at mil­lions of dol­lars, par­tic­u­larly on long- dis­tance f lights for which fuel is at a pre­mium.

The ecoDe­mon­stra­tor tested out the bug- slough­ing tech­nol­ogy in Shreve­port, La., which New­man called the bug cap­i­tal of the coun­try.

To come up with the right coat­ing, Wohl said his team con­sid­ered the shape of its sur­face on a mi­cro­scopic level and its chem­i­cal com­po­si­tion.

Their in­spi­ra­tion was the lo­tus leaf.

The lo­tus leaf needs op­ti­mum sun ex­po­sure for pho­to­syn­the­sis, he said, and so is adept at re­pelling wa­ter and dirt. But the sur­face of the lo­tus leaf isn’t slick — it’s rough.

The non­stick coat­ings that worked best to slough off bug guts are sim­i­larly rough, like f ine- grade sand­pa­per, and use sur­face ten­sion to help roll off in­sect re- mains.

“The residue is go­ing to come and hit, and it’s go­ing to trap air un­der­neath it,” Wohl ex­plained. “And that air’s go­ing to com­press. At some point, that air isn’t go­ing to com­press any­more, and it’s go­ing to re­verse and start to come back out. As it comes back out, this ex­pand­ing re­gion of the in­sect guts is try­ing to ex­pand. … It desta­bi­lizes that and kicks it off the sur­face.”

The non­stick tech­nol­ogy could also have ap­pli­ca­tions be­yond avi­a­tion, Wohl said, for such things as ship hulls, au­to­mo­biles and space­craft.

“One of the things I re­searched when I f irst came here were sur­faces that lu­nar dust wouldn’t stick to,” Wohl said. “There’s some carry- over be­tween these tech­nolo­gies that we’re de­vel­op­ing here where they could be ap­pli­ca­ble to, say, an ex­trater­res­trial, long- du­ra­tion mis­sion on the Mar­tian sur­face.”

The coat­ings are ready now for larger- scale in­ves­ti­ga­tions into dura­bil­ity and en­vi­ron­men­tal im­pact, he said. NASA is reach­ing out to com­pa­nies to gauge their in­ter­est in fur­ther tests of the ma­te­ri­als.

Pho­tog r aphs by Kaitlin McKe­own Daily Press

A TOUR I S LED on the Boe­ing ecoDe­mon­stra­tor 757 at NASA Langley Re­search Cen­ter. Flights to test the coat­ings were done in buggy Shreve­port, La.

AT THE NASA cen­ter in Langley, Va., in­tern Dy­lan Blaschke, left, shows the coated edge of the test plane.

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