It is a really good article. The section on titanium use in aerospace and Lockheed Martin’s A-12 and Blackbird spyplanes was excellent.
’Titanium was nearly as strong as stainless steel, but weighed 40% less. It was also incredibly corrosion-resistant, and maintained much more strength at elevated temperatures compared to aluminum. This made it potentially very useful for aerospace applications, where weight was at a premium and materials were often exposed to high temperatures.’
The A-12
In the late 1950s, Lockheed won a contract to develop a high-speed, high altitude reconnaissance plane for the CIA. Because it was the 12th iteration of a design codenamed “Archangel," it became known as the A-12. To meet the unprecedented performance requirements (a cruising speed of Mach 3 and a cruising altitude of nearly 90,000 feet), Lockheed needed a metal that would retain its strength at the hundreds of degrees the exterior of the plane would reach. This ruled out aluminum, leaving either stainless steel or titanium. Ultimately, titanium alloy was selected for the A-12, as it would cut the gross weight of the plane nearly in half.Titanium had never been used to such an extent on an aircraft, or anywhere else. Lockheed had worked with titanium on a small scale since 1949 but prior to the A-12 titanium had mostly been used for small components on jet engines. For several years, for instance, 50% of all titanium was used in the J-57 jet engine. But on the A-12, titanium would be used for nearly every part of the airplane – 93% of the gross weight of the A-12’s structure was titanium.The A-12 “practically spawned its own industrial base” (CIA 2012), and over the course of the program thousands of machinists, mechanics, fabricators, and other personnel were trained in how to work with titanium efficiently. As Lockheed gained production experience with titanium, it issued reports to the Air Force and to its vendors on production methods, and “set up training classes for machinists, a complete research facility for developing tools and procedures, and issued research contracts to competent outside vendors to develop improved equipment" (Johnson 1970).
The A-12 first flew in 1962. 14 years later, its successor, the better-known SR-71, set an airspeed record of nearly 2200 miles per hour, which remains unbroken today.
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