Fish / Kingfish
In the late 1950s, General Dynamics pursued a highly stealthy design concept to meet requirements set by the Central Intelligence Agency for a supersonic high-altitude reconnaissance aircraft to replace the Lockheed U-2. The design began as a B-58 parasite known as Super Hustler. It evolved into an independent aircraft optimized to cruise at 125,000 feet at a speed of Mach 6.25. This configuration, dubbed Kingfish, was to be built mostly of pyro-ceram (a heat-resistant and radar-attenuating ceramic material). Two Marquardt ramjets powered the aircraft in the cruise portion of its mission. Two retractable General Electric J85 turbojets provided power for takeoff and for acceleration to speeds at which the ramjets could be ignited.
In the fall of 1957 the CIA commissioned a study to determine the probability of detecting an airplane by radar with respect to its speed, altitude, and radar cross-section (RCS). This analysis indicated that supersonic speed significantly reduced the ability of conventional radar systems to detect an aircraft. After the U-2 was in service for several years, it was evident that continued development should be done on the use of aircraft for special reconnaissance missions. CIA invited Lockheed and General Dynamics to make certain proposals, which they did. In fact, a very lively competition was held, carrying on over an 18-month period.
During the first half of 1959, both Lockheed and Convair worked to reduce the radar cross section of their designs, with assistance from Franklin Rodgers of the Scientific Engineering Institute. In pursuing his antiradar studies, Rodgers had discovered a phenomenon that he believed could be used to advantage by the new reconnaissance aircraft. Known as the Blip/Scan Ratio but also referred to as the Rodgers' Effect, this phenomenon involved three elements: the strength of a radar return, the altitude of the object being illuminated by the radar, and the persistence of the radar return on the radar screen (Pulse-Position Indicator display). Rodgers determined that a high-altitude object moving two to three times as fast as a normal aircraft would produce such a small blip with so little persistence that the radar operator would have great difficulty tracking it, if indeed he could even see it.
Rodgers estimated that for an aircraft to take advantage of this Blip/Scan Ratio phenomenon it must fly at altitudes approaching 90,000 feet and have a radar cross section of less than 10 square meters, preferably not much over 5 square meters. However, for a Mach 3.0 aircraft to achieve such a small radar cross section, its designers would have to make many concessions in its structural design and aerodynamics.
The radical General Dynamics design, however, lost out to its competitor from Lockheed in August 1959. The resulting Lockheed airplane, the single-seat A-12, was the forerunner of the two-seat USAF aircraft more widely recognized as the SR-71 Blackbird.
By the summer of 1959, both firms had completed their proposals. In early June, Lockheed submitted a design for a ground-launched aircraft known as the A-11. It would have a speed of Mach 3.2, a range of 3,200 miles, an altitude of 90,000 feet, and a completion date of January 1961. Kelly Johnson had refused to reduce the aerodynamics of his design in order to achieve a greater antiradar capability, and the A-1l's radar cross section, although not great, was substantially larger than that of the much smaller parasite aircraft being designed by Convair.
The Convair proposal called for a small, manned, ramjet-powered, reconnaissance vehicle to be air launched from one of two specially configured Convair B-58B Super Hustler supersonic bombers. The FISH vehicle, a radical lifting body with a very-small-radar cross section, would fly at Mach 4.2 at 90,000 feet and have a range of 3,900 miles. Following a Mach 2.0 launch from the lengthened B-58B with uprated engines, two Marquardt ramjets would propel FISH during the Mach 4.25 cruise portion of its mission over the target area. In order to survive extreme aerodynamic heating and also have a minimal radar signature, the vehicle was to be constructed using PyroCeram (a ceramic glass having virtually zero thermal expansion under extreme heating conditions) and other heat-resistant, radar-attenuating materials. Once the FISH decelerated, two pop-out turbojets would bring it back to base [either the Pratt & Whitney JT-12 or the General Electric J85 ]. The ramjet exit nozzles and wing edges would be constructed of Pyroceram, a ceramic material that could withstand the high temperatures of very high speeds and would absorb radio-frequency energy from radar pulses.
Convair stated that the FISH could be ready by January 1961.
Convair's proposal depended on two uncertain factors. First and foremost was the unproven technology of ramjet engines. At the time, no aircraft in existence could carry a large, ramjet-powered craft into the sky and then accelerate to sufficient speed for the ramjet engines to be ignited. Since ramjet engines had only been tested in wind tunnels, there was no available data to prove that these engines would work in the application proposed by Convair. The second uncertain factor was the B-58B bomber that was supposed to achieve Mach 2.2 before launching the FISH above 35,000 feet. This version of the B-58 was still in the design stage.
The CIA funded Conair at a high rate compared to what Lockheed was given for their studies. Much emphasis was placed on the radar cross section of the aircraft to be chosen. Three substantial uncertainties beset the FISH, however: the unproven technology of ramjet engines; the unavailability of the B-58B that would fly fast enough to launch it; and the possibility that the B-58B could not reach the necessary speed, or that if it did, the FISH could not operate under post-launch conditions.
The Convair team ultimately concluded the vehicle’s size, propulsion system, and logistics were impractical. The Air Force’s cancellation of the B-58B project in June 1959 took the FISH out of the running. Conversion of the older, slower B-58A into a supersonic launching platform for the FISH was ruled out by the high cost and technical difficulties involved. Moreover, the Air Force was unwilling to part with two aircraft from the small inventory of its most advanced bomber. Even had the B-58B program not been canceled, however, the FISH proposal would probably not have been feasible. Convair engineers had calculated that the added weight of the FISH would prevent the B-58B from achieving the speed required to ignite the parasite aircraft's ramjet engines.
By July l959 Convair had come to the conclusion that they were unable to accelerate the B-58 carrying the ramjet-powered Super Hustler through Mach 1.0. It was also evident that a single ramjet flying a manned aircraft over Russia for covert reconnaissance was unfeasible from a reliability point of view. Convair had not made any important breakthroughs in the anti-radar field which would guarantee an invisible aircraft. In fact, much of the work Lockheed did on the A-11 was transferred directly to the Super Hustler.
The Convair proposal was unusable, but the Lockheed design with its high radar cross section was also unacceptable to the Land committee. On 14 July 1959, the committee rejected both designs. designs and continued the competition. Lockheed continued to work on developing a design that would be less vulnerable to detection, and Convair received a new CIA contract to design an air-breathing twin-engine aircraft that would meet the general specifications being followed by Lockheed.
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