The ‘shark skin’ technology that could make flying cheaper

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Halcyon66

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Sharkskin's been around for at least a decade, if not two (or three?). Take-up has never seemed to match the initial promise.
 
DWG said:
Sharkskin's been around for at least a decade, if not two (or three?). Take-up has never seemed to match the initial promise.
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First time I remember it being used was on the last 12m edition of the America's Cup in 1987. Dennis Connor's Stars and Stripes '87 used a plastic film application on the hull in addition to extensive CFD for the time on the novel winged keel design it used. Not exactly aerospace but there's been some cross pollination between the nautical and aviation industries that have benefitted both sectors.
 
In 1937, several scientists and engineers from the AVA-Göttingen research center started experiments with suction inlets installed in the wing of a Junkers AT. 1 light plane. During the flight tests program an efficiency of 22 per cent was obtained with a 20 hp suction device. In 1940 a lift coefficient of 5 was achieved using a 45 hp suction fan mounted in the engine of a Fieseler Storch AT.2.

Between 1941 and 1943 the Messerschmitt Bf 109 V-24 prototype was fitted with blown flaps to improve low-speed handling. By 1944 some tests were conducted at Daimler-Benz/Stuttgart with one Bf 109 G-6 fitted with a Caudron built aile soufflé and one 9,000 rpm suction-fan blower system built by AVA. But the suction at high transonic speed required a considerable amount of power.

In February 1940, the tailless jet fighter project Lippisch P 01-112 was fitted with a suction device powered by one Bramo/BMW 3302 turbojet. In April 1943, the Arado design team proposed to use the Ar 232 A-05 prototype as flying laboratory fitted with a suction boundary layer control system powered by a cold rocket Walter HWK RI-203.

All these suction devices involved cutting slots (Lüftungs) into an aircraft’s wings, but the first attempts to use multiple slots to increase the suction rate did not achieve satisfactory results. The problem of more efficient suction led the German engineers to new research into porous surfaces with small holes.

At the end of 1944, the German foamed-metallurgy conducted experiments with porous Aluminum/Iron/Bronze alloys using the superplastic-deformation/diffusion-bonding technology. The new porous material, named Luftschwamm by the Göttingen scientist, would allow to eliminate the air scoops of the transonic fighters by delaying 1/10 Mach the apparition of compressibility shockwaves. But the work was discontinued without explanation in 1945.

The mystery was finally solved in April 1963 during the Mach 0.77 tests flights performed by the Northrop X-21A; an experimental prototype fitted with a porous breathing wing with thousands of tiny slots with 0.0035-inch width. The results were doubtful practically, because of the obstructions of the slots by insects, dust, rain, and other environmental anomalies.



In October 1950 the British had the same problem with the suction mechanisms of the laminar flows wings in the Armstrong Whitworth A.W.52 prototype.
 
DWG said:
Sharkskin's been around for at least a decade, if not two (or three?). Take-up has never seemed to match the initial promise.
Click to expand...
From my admittedly imperfect memory of back in the day popular German sci-tech magazines I tend to concur with your three decades estimate. "Quo magis res mutantur, eo magis manent eadem" (and while we're at it, as a fully recovered ex-catholic, also my sincere shutout to Pope Leo 14, who graduated from Villanova with a bachelor's degree in mathematics (as an engineer I f*ing hate roman numerals with a vengeance!).
 
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