Convair Kingfish

Convair Kingfish

Even as the U-2 entered operational service in 1955 the CIA were already drawing up plans for its eventual replacement and this eventually resulted in the delivery of the Lockheed A-12 Blackbird and later the larger Lockheed SR-71. However, Lockheed were not the only company the CIA approached to investigate the U-2 replacement and the other company Convair came up with a proposal that was unusual and innovative for its time and, because it never entered operational service, it remains relatively little known to this day – the Convair Fish and Superfish.

When the U-2 was first proposed to the US government, Lockheed engineers predicted that the aircraft would be able to fly sufficiently high to remain above Soviet radar cover, allowing the aircraft to conduct overflights of the USSR and surrounding Warsaw Pact countries without their military and political authorities being aware of what was taking place. However, when the U-2 actually entered service with the CIA and began over-flying countries in Eastern Europe and the USSR, the CIA discovered to their alarm that the U-2s were consistently tracked by Warsaw Pact radars throughout the majority of their sorties. The Soviets made discrete written diplomatic protests about these over-flights, but were reluctant to complain publicly because they didn’t want the rest of the world to know that they lacked the military capability to do anything other than complain in writing. With this in mind, for the planned U-2 replacement, Lockheed and Convair were asked to develop proposals that would have the lowest possible Radar Cross Section (RCS) as well as being able to fly at extreme altitude and high supersonic speeds.

Rather than opt for a conventional aircraft powered by turbojet engines, Convair decided that a ramjet engine offered the best solution to sustained high-speed flight, however, the problem with ramjets is that they need an airflow through their combustion chamber of around Mach 2 before they can be started, making it impossible for their design to make a conventional take-off. To overcome this limitation, Convair decided to propose the use of a larger, faster version of their B-58A Hustler bomber, known as the B-58B Super Hustler, as the launch platform for a combination of manned and unmanned vehicles, known as ‘parasites’. The manned ‘parasite’ consisted of a 46.58 ft long winged vehicle, with a wingspan of 18.75ft, carrying a two-man crew, powered by a single Marquardt RJ-59 ramjet delivering 10,00lbs of thrust at Mach 3 and 5,000lbs of thrust and Mach 4. A small turbojet was also installed to provide power during the landing phase when the vehicle would be going too slow for the ramjet to function. The unmanned ‘parasite’ was 48.75ft long with a wingspan of 23.33ft, weighted around 25,300lbs and was powered by two Marquardt RJ-59 engines. Both ‘parasites’ were constructed mainly of stainless steel, a ceramic material known as Pyro-Ceram and titanium to enable them to survive the intense heat generated by Mach 4 flight. The cockpit windows were also protected with heat shields and the crew were provided with outside visibility by television cameras.

Convair Super Hustler with parasites

Convair’s plan called for the ‘parasites’ to be ‘mated’ to the lower fuselage of the Super Hustler, with the manned component in the front and attached by its tail to the unmanned component at the rear. Then, with both ‘parasites’ in place, the Super Hustler would take-off from a conventional runway and climb to maximum altitude and Mach 2, before starting the three ‘parasites’ ramjets before launching them both around 2,300 miles from the target area. After launch, with the ‘parasites’ engines producing full power, the combination would climb to an altitude of around 75,000ft and eventually settle into a cruise at Mach 4, whilst slowly climbing to 90,000ft as fuel was burnt off. As the target was approached, the unmanned ‘parasite’ would be released to deliver a nuclear weapon to a separate high priority, heavily defended target. In a pure reconnaissance role, the unmanned ‘parasite’ would be used to carry additional fuel for the manned ‘parasite’ and then jettisoned when the fuel ran out. After the target was overflown, the manned ‘parasite’ would exit the area at Mach 4 before engaging its turbojet engine and landing conventionally on a runway using a wheeled nose gear and fuselage skid – visibility on final approach was improved by a nose that was hinged and could be moved down.

Convair Fish

Despite some individuals in the USAF expressing an interest in the Super Hustler, the reality was that the cost of operating and maintaining the unreliable, complex, high-speed B-58 was beginning to raise many questions. Many other individuals in SAC, not least the C-in-C Curtis LeMay, began to question whether these aircraft were worth the trouble particularly when the reliable, long-range Boeing B-52 began to enter service and could be operated in greater numbers and at a much lower cost. More importantly, the idea of a parasite bomber gathered little support and the concept never received official government funding. However, the CIA were still interested in a supersonic reconnaissance aircraft and encouraged Convair to continue to develop their ‘parasite’ proposal. However, this time Convair’s Bob Widmer and Vincent Dolson came up with a slightly different concept. This time, rather than a twin manned and unmanned concept, they decided that the ‘parasite’ aircraft carried by the B-58B Super Hustler would be a single manned aircraft that they named the Fish. The Fish was once again powered by two Marquardt RJ-59 ramjet engines that would give the aircraft a top speed of Mach 4.2 at 90,000ft, a range of 3,900 nms, and was also fitted with two turbojets that would enable the aircraft to make a powered landing. The design employed a lifting body fuselage shape and again the leading edges and engine intakes were constructed of pyro-ceram, helping to reduce the RCS.

Convair Fish

However, although the new Convair proposal was an improvement on the original twin ‘parasite’ proposal, it still made two risky assumptions; namely that the Marquardt RJ-59 ramjets would produce sufficient power to achieve the planned top speed and that the B-58B Super Hustler would be able to carry the fairly heavy Fish up to the launch speed of Mach 2.2 to start the ramjets and a number of Convair staff believed this was unlikely to be achieved. However, what eventually brought this concept to an end in 1959 was the USAF decision not to proceed with the B-58B. Although Convair investigated the possibility of converting the smaller, lighter B-58A to launch the Fish, it was quickly realised that this was impossible. Many others also believed that the concept of launching the Fish would also have been too costly in logistical support.

Convair Kingfish

Convair got the message about the mothership and ramjet engines concept, went back to the drawing board and came up with a completely new design for a more conventional aircraft powered by the P&W J-58 turoramjet engine that would also power the Lockheed proposal – the A-12. The new Convair design was a delta wing aircraft named the Kingfish, carried a two man crew in tandem seats equipped with escape capsules and was powered by two J-58s engines carried internally. The cruise speed of the Kingfish was planned to be less than the Fish at Mach 3.2, but was similar to the Lockheed A-12 , however the range was greater at 3,400nms. In theory the great advantage the Kingfish had over the A-12 was its reduced RCS, thanks to its fairly smaller size, internal engines and the use of pyro-ceram along the leading edges and engine inlets, although Kelly Johnson of Lockheed disputed these claims.

In Aug 1959 Lockheed and Convair submitted their two proposals, the A-12 and Kingfish, to a review panel that consisted of representatives of the Dept of Defence, USAF and the CIA. Although the Kingfish was favoured by some because of its lower RCS, the Lockheed proposal finally won the day, having greater range, a higher max cruise altitude and was cheaper to build. However, what probably won the day for the Lockheed A-12 was that Lockheed had already delivered the U-2, a highly unusual and advanced design, in secrecy, on time and on budget and then the U-2 had then gone on to deliver the required performance in operational service – in comparison Convair had no similar background.

Convair Kingfish

Of course one question will always remain unanswered, if the Kingfish had been selected rather than the A-12, would it have performed as well as the A-12 and of course without the A-12 there would have been no SR-71. In the event Lockheed encountered numerous difficulties in developing the A-12, so it’s reasonable to assume that Convair’s engineers could also have found similar solutions for the Kingfish. The P&W J-58 engines and the complex inlet control system were the real key to the A-12’s ability to cruise at Mach 3+, whether the more conventional intakes on the Kingfish would have delivered the same level of performance remains debateable. Nevertheless, what is beyond dispute is that the Kingfish looked superb for an aircraft designed in the late 1950s and, if the twin tails were canted inboard to reduce the RCS, it could easily pass for an early F-117 Stealth Fighter. It is a great pity that the Kingfish was never built and flown, but nevertheless this design stands the test of time and is a suitable tribute to the skill and foresight of the Convair designers.