The Lockheed A-12 is a retired high-altitude, Mach 3+ reconnaissance aircraft built for the United States Central Intelligence Agency (CIA) by Lockheed's Skunk Works, based on the designs of Clarence "Kelly" Johnson. The aircraft was designated A-12, the twelfth in a series of internal design efforts for "Archangel", the aircraft's internal code name. In 1959, it was selected over Convair's FISH and Kingfish designs as the winner of Project GUSTO, and was developed and operated under Project Oxcart. The CIA's representatives initially favored Convair's design for its smaller radar cross-section, but the A-12's specifications were slightly better and its projected cost was much lower. The companies' respective track records proved decisive. Convair's work on the B-58 had been plagued with delays and cost overruns, whereas Lockheed had produced the U-2 on time and under budget. In addition, Lockheed had experience running a highly classified "black" project. The A-12 was produced from 1962 to 1964 and flew from 1963 to 1968. It was the precursor to the twin-seat U.S. Air Force YF-12 prototype interceptor, M-21 launcher for the D-21 drone, and the SR-71 Blackbird, a slightly longer variant able to carry a heavier fuel and camera load. The A-12 began flying missions in 1967 and its final mission was in May 1968; the program and aircraft were retired in June. The program was officially revealed in the mid-1990s. A CIA officer later wrote, "Oxcart was selected from a random list of codenames to designate this R&D and all later work on the A-12. The aircraft itself came to be called that as well." The crews named the A-12 the Cygnus, suggested by pilot Jack Weeks to follow the Lockheed practice of naming aircraft after celestial bodies.
Design and development
Background With the failure of the CIA's Project Rainbow to reduce the radar cross-section (RCS) of the U-2, preliminary work began inside Lockheed in late 1957 to develop a follow-on aircraft to overfly the Soviet Union. Designer Kelly Johnson said, "In April 1958 I recall having long discussions with [CIA Deputy Director for Plans] Richard M. Bissell Jr. over the subject of whether there should be a follow-on to the U-2 aircraft. We agreed ... that there should be one more round before satellites would make aircraft reconnaissance obsolete for covert reconnaissance." Under Project Gusto the designs were nicknamed "Archangel", after the U-2 program, which had been known as "Angel". As the aircraft designs evolved and configuration changes occurred, the internal Lockheed designation changed from Archangel-1 to Archangel-2, and so on. These names for the evolving designs soon simply became known as "A-1", "A-2", etc. The CIA program to develop the follow-on aircraft to the U-2 was code-named Oxcart. A-4 through A-6 concepts applied blended wing/fuselage configurations with combinations of turbojet, ramjet, and rocket propellant. However, these concepts never met the required range. Concepts A-7 thru A-9 used a single J58 afterburning turbojet plus two Marquardt XPJ-59 ramjets burning JP-150 fuel.
Design concept A-10 featured a pair of General Electric J93-3 turbojets with 2-D underwing inlets and had better mission radius than concepts A-4 thru A-9. These designs had reached the A-11 stage when the program was reviewed. The A-11 was competing against a Convair proposal called Kingfish, of roughly similar performance. However, the Kingfish included a number of features that greatly reduced its RCS, which was seen as favorable to the board. Lockheed responded with a simple update of the A-11, adding twin canted fins instead of a single right-angle one, and adding a number of areas of non-metallic materials. This became the initial A-12 design. On 26 January 1960, the Central Intelligence Agency officially ordered 12 A-12 aircraft with the contract signed on 11 February 1960. Lockheed charged $96.6 million for design, manufacture and testing of 12 aircraft.
New materials and production techniques
Because the A-12 was well ahead of its time, many new technologies had to be invented specifically for the Oxcart project with some remaining in use to present day. One of the biggest problems engineers faced at the time was working with titanium. In his book Skunk Works: A Personal Memoir of My Years at Lockheed, Ben Rich stated, "Our supplier, Titanium Metals Corporation, had only limited reserves of the precious alloy, so the CIA conducted a worldwide search and using third parties and dummy companies, managed to unobtrusively purchase the base metal from one of the world's leading exporters – the Soviet Union. The Soviets never had an inkling of how they were actually contributing to the creation of the airplane being rushed into construction to spy on their homeland." 93 percent of the A-12's structure was titanium.
Before the A-12, titanium was used only in high-temperature exhaust fairings and other small parts directly related to supporting, cooling, or shaping high-temperature areas on aircraft like those subject to the greatest kinetic heating from the airstream, such as wing leading edges. The A-12, however, was constructed mainly of titanium. Titanium is rigid and difficult to machine, which made it difficult to form into curves given available techniques. This made it difficult to form the leading edges of the wing and similar surfaces. The solution was found by machining only small "fillets" of the material with the required shape and then gluing them onto the underlying framework which was more linear. A good example is on the wing: the underlying framework of spars and stringers formed a grid, leaving triangular notches along the leading edge that were filled with fillets. With the move to the A-12, another improvement in RCS was made by replacing the fillets with new radar-absorbing composite materials made from iron ferrite and silicon laminate, both combined with asbestos to absorb radar returns and make the aircraft more stealthy. To further reduce the detectability of the aircraft's afterburner plumes a special cesium additive nicknamed "panther piss" was added to the fuel.
Flight testing
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