Following recommendations by the Land committee, both Lockheed and Convair incorporated the Pratt & Whitney J58 power plant into their designs. This engine had originally been developed for the Navy's large, jet-powered flying boat, the Glenn L. Martin Company's P6M Seamaster, and was the most powerful engine available. In 1958 the Navy had canceled the Seamaster program, which had left Pratt & Whitney without a buyer for the powerful J58 engine.
FISH was scrapped in favor of a larger vehicle that could function autonomously, without the need for a launch aircraft. Toward the end of July 1959, Convair was given another contract to design an air-breathing twin-engine airplane known as the Kingfish. Built around two side-by side Pratt & Whitney JTD11D-20 (J58) engines mounted in the fuselage, was to be capable of a top cruise speed of approximately Mach 3.25 at an altitude of 125,000 feet. The vehicle’s wing edges were to be built in a complex pattern of interlocking wedges, every other one made of radar-absorbent material to reduce the RCS. Convair built a model of the KINGFISH airframe for radar signature tests, but never produced a flyable airframe. This airplane actually used rectangular plastic after-burners [which could not conceivably work]. The radar cross setion was not better than Lockheed's A-12.
By the late summer of 1959, both Convair and Lockheed had completed new designs for a follow-on to the U-2. Convair's entry, known as the KINGFISH, used much of the technology developed for the F-102, F-106, and B-58, including stainless steel honeycomb skin, planiform wing design, and a crew capsule escape system, which eliminated the need for the pilot to wear a pressurized suit. The KINGFISH had two side-by-side J58 engines inside the fuselage, which significantly reduced the radar cross section. Two additional important design features that contributed to a small radar return were fiberglass engine inlets and wings whose leading edges were made of Pyroceram.
Convair and Lockheed submitted their designs to a selection panel with members from the Department of Defense, the Air Force, and CIA on 20 August 1959. Convair's proposal was a ramjet-powered Mach 4.0 piloted aircraft to be launched on the B-58. They stayed with this design a considerable period of time. Some of the CIA representatives initially favored the Convair KINGFISH design because of its smaller radar cross section, but they were eventually convinced to support the Lockheed design by the Air Force members of the panel, who believed that Convair's cost overruns and production delays on the B-58 project might be repeated in this new project. In contrast, Lockheed had produced the U-2 under budget and on time. Another factor favoring the A-12 was security. Lockheed had experience in running a highly secure facility (the Skunk Works) in which all of the key employees were already cleared by the Agency.
The A-12’s specifications were slightly better than the KINGFISH’s, and its projected cost was significantly less. Convair’s design had the smaller RCS, however, and CIA’s representatives initially favored it for that reason. 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, it had experience running a “black” project.
|Max Speed||Mach 3.2||Mach 3.2|
|Max Range [nm]||4,120||3,400|
|Initial Cruise Alt [ft]||84,500||85,000|
|Max Cruise Alt [ft]||97,600||94,000|
|Radar Cross Section||(higher)||(lower)|
|Unit Cost (w/o engines)||$8.05 million||$10.1 million|
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