Kevin John Parrish

Paint it Black! Making one of the first titanium airplanes was difficult. Titanium was corrugated to allow room for expansion when it heated up at top speeds of 2200+ mph. The skin panels were fastened to the underlying structure with oblong holes that allowed the skin to expand and contract without the fasteners causing buckling. The skin over the wing was also corrugated to prevent warping during expansion; this is quite noticeable. You can see the corrugated sections quite clearly in this artistic photo. Titanium makes up 93% of the SR-71 structure. Its strength-to-weight ratio, or specific strength, is better than Aluminum. Yet very little titanium is used in everyday objects today. Planes primarily use aluminum, not titanium. Why is it not used? The development of the A-12, the Skunk Works, a small division of Lockheed, discovered that making the blackbird out of titanium was going to be anything but easy Titanium is expensive because its refinement process is a nightmare. To make Titanium, we start with a feedstock in the form of Titanium Dioxide, with this chemical formula. This oxide ore, called rutile, occurs in high concentrations in dark sandy soils. To build the SR-71, the US needed to buy vast quantities of the mineral from the Soviets. To do this, they purchased the material through ghost organizations to hide the material's final destination. One of the made-up companies was supposedly a pizza-oven manufacturer… the Russians believed this story! Had the Soviets known what they were helping build, they would not have sold the material. However, the US likely could have just purchased the material from mines in Australia. This is a relatively common raw material, primarily used as a white pigment in paints, and it is even found in sunscreen lotion as an ultraviolet-radiation-blocking pigment. The primary titanium alloy used in the SR-71 was 13 percent vanadium, 11 percent chromium, and 3 percent aluminum. Both Chromium and Aluminium form thermally stable oxide layers on the outer skin of the metal. This prevents oxygen from diffusing further into the metal and making it more brittle. This raises the metal's maximum operating temperature! Vanadium acts as a stabilizer for a crystal structure referred to as the beta phase. This leads to a material with higher tensile strength and better formability, through trial and error and problems solved by the geniuses who worked at the Skunk Works. They discovered that their cadmium-plated tools left trace amounts of cadmium on bolts, which caused galvanic corrosion and made the bolts fail. This discovery led to removing all cadmium tools from the workshop. This article proves what we already know: when people work together and work hard to solve problems. New ground was broken with the formulation of titanium, which led to the success of the SR-71 and the tremendous heat and strength this magnificent airplane needed. As Ben Rich, head engineer and later replacing Kelly Johnson as the “head skunk,” said in his book called The Skunk Works. ‘’I volunteered some unsolicited advice about how we could use a softer titanium that began to lose its strength at 550° to paint the airplane black From my college days, I remember that a good heat absorber was also a good heat emitter; it would actually radiate away more heat than it absorbed through friction. I calculated that the black paint would lower the wing temperature by 35° through radiation; think of how much easier it would be to build an airplane using softer titanium. My father, Butch Sheffield, worked for Ben Rich; Ben Rich saved the Blackbird program time and money with his idea of painting it black. wisconsinmetaltech.com/titan… is my source,The Skunk Works by Ben Rich Linda Sheffield