An initial batch of 50 motors was delivered to Lockheed in 1963 for fitting in the A-12 and the YF-12s. A second batch of one hundred examples was dispatched in 1964 to equip the SR-71s.
Pratt & Whitney had great plans for their JT-11 super engine. They saw the prototype and the those as JT-58s destined for the Blackbirds unfolding into a production series. Adaptations of this motor were proposed for all the design studies of the period for hypersonic programs, much treasured in the 1950s - 1960s, such as the SST or the Convair BJ-58. This latter four-engine design, also known as the B-58C, was contemplated as a supersonic transport flying at Mach 2.5 and cruising at more than 70,000 ft (21,300 m), powered by four J-58s (without after-burning) of 23, 000 lbs thrust (10.400 kgp) mounted in two wing-tip nacelles.
A military version of this Convair model 58-9 was also announced under the name of model 62. It would have had the capability to transport 52 troops. Twin-engine interceptor variants called B-58D (for Air Defense Command) and B-58S (for the Tactical Air Force) were also proposed fitted with J-58s capable of propelling a load of more than 30,000 lbs (13.600 kg). It is likely that the Pentagon encouraged this profusion of projects using these engines so as not to draw attention to the A-12.
Much later development of a double-flux version of the J-58 using compressors of greater size was contemplated.
At the same time Pratt & Whitney proposed a nuclear version of the J-58 using an indirect propulsion cycle, fuelled by a solid-fuel reactor cooled by a twin line system? The USAF intended being equipped with a guided missile capable of low-altitude penetration. The program, named CAMAL was cancelled in 1960, but it had demanded of Convair, involved with the project - in competition with Pratt & Whitney and General Electric, construction of two subsonic NX-2 aircraft to experiment with the mode of propulsion.
These studies mainly permitted a comparison of the two classes of nuclear flux engines, those envisaged by General-Electric (the simplest but dirtier system as the radioactive material was sent directly into the combustion chambers) or those using the indirect cycle proposed by Pratt & Whitney which utilized liquid sodium as a high-temperature conductor between the nuclear reactor and the combustion chambers of the J-58 propulsion unit.
The planes would fly in 1965 under the designation of WS-125A/L, but had been registered in 1961 as a back-up for the WS-110A "Weapon System" which gave birth to the North American XB-70 Valkyrie. Certain Pratt & Whitney nuclear reactors were adopted a little later by the commission for nuclear energy in its "System for Nuclear Auxiliary Power" (SNAP) However, despite some trial installations of a nuclear reactor aboard a giant B-36 bomber (alias the X-6) no atomic propulsion unit would ever be air-tested. Not even the General Electric system, design of which had progressed further than that of Pratt & Whitney's system.
The description of another project derived from the J-58, namely the SNECMA M-35 is of equal interest. In 1959 the French SNECMA company signed a partnership agreement with Pratt & Whitney which offered enviable prospects. Not least because, at the start of the nineteen-sixties, France decided to conquer the challenge of supersonic-transport, SNECMA thus had to design a propulsion system for the future aircraft. That led to negotiations concerning the possibility of manufacturing under license the JT-11B3, a civil variant which was being proposed at the then stage of J-58 development. The Franco-British agreement of 1961, brought an end to this project, with the decision to equip the future "Concorde" with a turbojet of British origin. However, one sometimes finds reference to the M-35 engine among the many Mach-3 aircraft projects fashionable in France at that time.
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