A-12 OXCART Blackbird
The A-12 Blackbird was the first airplane made largely of titanium, a strong, light metal. As a reconnaissance platform, the A-12 was flown exclusively by the CIA. It accommodated a single pilot in a full pressure suit. The first airframe was delivered in February 1962 and made its maiden flight two months later. Test flights and operational missions continued until the airplanes were retired in June 1968. Just as the A-12 was about to be declared operationally ready, US policymakers decided to replace it with the Air Force’s OXCART reconnaissance variant, the SR-71. The most advanced aircraft ever built was decommissioned after less than a year in service.
As early as 1956, just as the U-2 was becoming operational, Lockheed's Kelly Johnson proposed a Mach 2.5 hydrogen-fueled airplane capable of cruising above 99,000 feet. Only 25 people were cleared into this special access program, code-named SUNTAN. Lockheed’s initial SUNTAN studies evolved into a vehicle nearly 300 feet long with a gross takeoff weight of 358,500 pounds. Johnson’s CL-400 design posed numerous technical challenges involving materials, manufacturing, airframe/powerplant integration, and fuel production, storage and handling.
Boeing had proposed a hydrogen powered airplane having a gross weight of 167, 000 pounds and a length of over 200 feet. At this time, Lockheed had just conecluded work on a hydrogen powered aircraft and concluded that the range obtainable was quite insufficient. As technological problems began to overwhelm the project, Johnson began to have serious doubts about its viability. So the CL-400 was dropped. In February 1959, SUNTAN was finally terminated at Johnson’s request and his final design, the hydro-carbon-fueled CL-400-15JP, served as a steppingstone to the Archangel project that eventually yielded the A-12.
On 23 July 1958, Johnson presented his concept to the advisory committee select a design for the U-2’s successor. The A-11 aircaft was a design which made no compromises for the anti-radar design. Chaired by Polaroid chief executive Edwin Land, the committee, which expressed interest in the approach. But the Land committee rejected the A-11 because its RCS was too large.
On 29 August 1959, the selection panel voted for the A-12 but required Lockheed to demonstrate by 01 January 1960 that it could reduce the aircraft’s RCS sufficiently. CIA awarded a four-month contract to Lockheed to proceed with antiradar studies, aerodynamic structural tests, and engineering designs. OXCART was selected from a random list of codenames to designate this R&D and all later work on the A-12.
In the course of this phase of radar testing and after, which required a full-scale, pylon-mounted mock-up, and further wind tunnel tests, the A-12 took on more of its distinctive cobra-like shape that allowed for better dispersion of radar pulses. To further reduce those reflections, the two canted rudders were fabricated from laminated non-metallic materials — the first time such substances had been used for an important part of an aircraft’s structure. (Later on, the production aircraft would be painted with a radar-absorbent coating of ferrite particles in a plastic binder.)
The A-12 which was finally built made substantial design changes to reduce its cross section. To overcome the afterburner problem of a large radar cross section return from the aft quadrant, Lockheed proposed the use of cesium additive to the fuel. This was first brought up by Mr. Ed Lovick of ADP, and its final development was passed over to P&W. It was eventually a basic part of Lockheed's cross section reduction methods. Lockheed proved by 01 January 1960 that their concept of shape, cesium fuel additive;, and loaded plastic parts had enough promise to warrant going forward with the project.
On 14 September 1960, Johnson began work on a bomber version of the Blackbird that he called the RB-12. His proposal resulted from the reported development of small, high-yield nuclear warheads. He suggested that four hypothetical 400-pound bombs, or a single large bomb, could be carried inside the airplane’s fuselage without compromising fuel load. No aerodynamic changes were required and the radar-attenuating features remained intact. Johnson pitched his proposal to the Air Force, emphasizing the airplane’s performance and survivability characteristics. Although Johnson found the Department of Defense more interested in the bomber than the interceptor, the RB-12 never went beyond the mock-up stage. It was ultimately rejected because it was seen as a threat to North American Aviation’s XB-70, the proposed replacement for the B-52.
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