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The Blackbird
The SR-71, unofficially known as the “Blackbird,” was a long-range, Mach 3+, strategic reconnaissance aircraft developed from the Lockheed A-12 and YF-12A aircraft.
The first flight of an SR-71 took place on Dec. 22, 1964, and the first SR-71 to enter service was delivered to the 4200th (later 9th) Strategic Reconnaissance Wing at Beale Air Force Base, Calif., in January 1966.
The Blackbird was in a different category from anything that had come before. “Everything had to be invented. Everything,” Skunk Works legendary aircraft designer Kelly Johnson recalled in an interesting article appeared on Lockheed Martin website.
Production of the SR-71 was done at the Skunk Works plant, in Burbank, California, as the photos in this post show [the image were taken in 1965 and show some of the first SR-71 under construction: featured in the pictures are the first B models (957 and 956) under construction with an A-model (955). My dad Richard “Butch“ Sheffield told me that he watched these airplanes under construction at the Skunk Works plant at Burbank].
SR-71 airframes built almost entirely of titanium
The airframes were built almost entirely of titanium and other exotic alloys to withstand heat generated by sustained high-speed flight: in fact, the Blackbirds were designed to cruise at Mach 3 continuously for more than one hour at altitudes up to 85,000 feet.
Blackbird’s engineers had a perplexing problem as to why some of the titanium was corroding. However, they figured out the reason. It was chlorine in the water!
According to Wisconsin Metal Tech, the engineers of the SR-71 were among the first people in history to make real use of the material. In that process, they ended up throwing away a lot of material, some through necessity, some through error. At times the engineers were perplexed as to what was causing problems, but thankfully they documented and cataloged everything, which helped find trends in their failures.
Spot welded parts made in summer corroded while those made in winter didn’t
They discovered that spot welded parts made in the summer were failing very early in their life, but those welded in winter were fine. They eventually tracked the problem to the fact that the Burbank water treatment facility was adding chlorine to the water they used to clean the parts to prevent algae blooms in summer, but took it out in winter. Chlorine reacts with titanium, so they began using distilled water from this point on.
They discovered that their cadmium plated tools were leaving trace amounts of cadmium on bolts, which would cause galvanic corrosion and cause the bolts to fail. This discovery led to all cadmium tools to be removed from the workshop.
Be sure to check out Linda Sheffield Miller (Col Richard (Butch) Sheffield’s daughter, Col. Sheffield was an SR-71 Reconnaissance Systems Officer) Twitter X Page Habubrats SR-71 and Facebook Page Born into the Wilde Blue Yonder Habubrats for awesome Blackbird’s photos and stories.
Lockheed photos via Tony Landis and CIA
