By the end of May 1956, Hughes and Sperry had received contracts (dated "February 1956 and December 1955, respectively) for the development of an advanced fire control system for the long range interceptor and Sperry's had been cancelled (in May 1956). Hughes and Ramo-Wooldridge had completed studies of the requirements and specifications for a fully integrated system employed in an aircraft operating during the 1960s, giving special consideration to the possibility of installing such a unit in the proposed F-103 aircraft. The work at Sperry and Hughes was to have resulted in an ultimate system available early in 1962. Until that time, the Air Force had already indicated it was prepared to appoint the long range interceptor with a modified MA-1 system (the MX-1179) with a 40 inch antenna. By May, the Hughes proposal for this project was being evaluated in Dayton.
In September 1956, the Pentagon brought the Radio Corporation of America into the program and Hughes and RCA were then charged with development of prototype systems.
Ramo-Wooldridge recommended a high-burst, time fuzed, nuclear warhead rocket, with a Falcon-type infrared missile as auxiliary armament. The nuclear warhead projectile would contain an autopilot, would be preset for flight before launch, and would be able to make a 90 degree turn after launch. The armament would be capable of reaching a target in a very short time period, which would minimise the effect of target maneuver. Since it was pre-guided, it could not be jammed. In association with this new weapon, Ramo-Wooldridge also recommended a lower frequency radar with improved counter-counter measures equipment, and a suitable computer as well as a new technique for hitting high-flying bombers from interceptors at lower altitudes.
The Hughes proposal was predicated on the use of a GAR-X type missile with an interchangeable nuclear or high explosive conventional warhead and an advanced radar or infrared guidance system plus a proximity fuse. Hughes proposed a similarly advanced, though higher frequency radar. In general the Ramo-Wooldridge studies included a more radical approach and seemed best suited for possible future development.41
Little work could be expected on a fire control system designed for an aircraft which was not to be developed but not everyone was so sure that the future of the long range interceptor had been sealed forever. Soon after the act of cancellation, General Partridge proposed a "modified" long range interceptor for consideration. This was a Mach 2.5 vehicle capable of attaining an altitude of 70,000 feet or more with a radius of 300 to 350 nautical miles, one pilot, and a modified MX-1179 fire control system. The general wanted Washington to award North American a contract for development of this interceptor but the Pentagon demurred and instead decided to evaluate the new proposal in conjunction with the older long range interceptor concept established by the same contractor as well as some other variations on the same theme receiving attention at the time.
Finally, the Air Staff met and decided that the old standard long range interceptor was indeed just what the Air Force needed, but that now it should be developed in combination with advanced air-to-air missiles. This decision was supported, and the concept for the new long range interceptor was expanded, by a special generals board (chaired by Major General Albert Boyd, the WADC commander) which concluded its evaluation of the situation in February 1957.
[The board also included Major Generals James Ferguson, Hugh A. Parker, and K. P. Berquist, Col. J. F. Mocenry, and Dr. C. D. Perkins.]
The board reported (directly to the Air Force Chief of Staff) that a ''two-place manned interceptor, capable of attaining a speed of Mach 3.0, altitudes of 70,000 feet plus, and a radius of action of 1000 miles under optimum cruise conditions is essential to the defense of the United States during this period." Such an aircraft had to be able to cruise subsonically and dash at supersonic speeds. For the dash mission, a radius of 350 nautical miles would be necessary, while on "optimum" cruise mission, a 1,000 nautical mile radius would be required.
For the all weather fire control system, the board first required that the equipment be compatible with the flight regime and performance of the air vehicle. Next, they stated that detection ranges "in the order of 80-100 nautical miles, missile ranges of 15-25 nautical miles, and altitude differentials up to 40,000 feet are feasible." They also urged that the system be "designed to take advantage of human capabilities of the cycle of fire control operation."
Further defining the functions and characteristics desired of the fire control system, General Boyd and his compatriots established that the interceptor would "require solid communications" for the 1,000 nautical mile radius and that the navigation system should be incorporated into the fire control system. The fire control system itself was to be "able to operate effectively under close control, modified close control, and under no control conditions." This control was to be exercised by SAGE, airborne radar aircraft, and picket ships.
In addition to the established detection range, the generals felt that a "lock-on range approaching the detection range is considered essential in order to take full advantage of the armament system in an 'all around attack' against targets ranging from subsonic to speeds in excess of Mach 3." Since effective "operation in a counter-measures environment and at altitudes from sea level to above 70,000 feet" was required, the group recommended "that the dual use of pulse doppler radar and infrared detection" was the best solution to the problem.
For a high degree of versatility, the board recommended two types of armament, conventional guided missiles (cast in the Falcon mould), and at least two GAR-X missiles meeting the 15 to 25 mile requirement, capable of use with an "interchangeable HE-atomic warhead." The minimum size for the atomic warhead was established at two kilotons. To reduce the effect of countermeasures, the Boyd group also recommended that the missile have both electronic and infrared guidance.
Finally, the board urged that maximum reliability, simplicity, and ease of maintenance be established as the goals of the fire control and armament systems.
Heeding this analysis, Washington re-instated the long range interceptor on 11 April 1957, ordering development laid down by the generals in February. Fifteen days later ARDC provided the framework for the future of the fire control and missile portions of the new long range interceptor program. First of all, command headquarters decided that the contractors would sign one agreement covering the fire control system and the missile. Next, although one contractor was to be approved as the principal party in this effort, a second source was to be selected "in case HQ USAF makes sufficient funds available to support a competitive development of the complete armament system to a point where a decision can be made based on test results."
Baltimore decreed that the missiles would have to be capable of a 15 to 25 nautical mile range, the 40,000 foot altitude differential established by the February generals board, and semi-active terminal guidance. Passive terminal guidance was required as a secondary device and ARDC stated it would be most happy to see this type of unit installed, along with the primary guidance equipment, in one missile. The missile was also to be launched after a minimum of aircraft positioning.
For the fire control system, ARDC required the unit to be designed so that it comprised a pulse doppler mode (with an additional mode based on pulse-to-pulse shifting "if feasible"), an 80 to 100 nautical mile search range, and infrared search and tracking. It was also to be capable of directing the launch of alternate infrared missiles.42
North American was on contract for development of the long range interceptor—now dubbed the F-108—in June, but the commencement of actual development had to await some further clarifications. With the sir Defense Command stressing the value of the medium range interceptor, the contractor was not quite certain that the F-108 should be designed strictly for the long range task and in July asked for a formal decision on the role expected of the new weapon system. The answer was that while the F-108 was to be designed "primarily to the long range interceptor mission," it was to contain ''provisions for off-loading to perform the medium range and scramble-from-loiter missions."
By this time, Hughes had been accepted as the sole "Missile and Fire Control System" contractor for the F-108. The decision to approve Hughes was based in part on the high cost of maintaining two contractors and a North American evaluation of the proposals prepared by Hughes and RCA. North American gave Hughes a "slight advantage" over RCA, but stated that either would be satisfactory.
Hughes had the edge in the field of countermeasures and ECM was certainly a critical area. Still, North American felt that the RCA system was capable of achieving greater flexibility in operations, but that this would mean higher complexity. In very general terms, the degree of complexity in the equipment proposed by RCA offered more performance at the cost of reliability (especially because the radio corporation proposed an inertial platform for the heart of the system), increased maintenance problems, and increased weight.
Once Hughes was established as the fire control system and missile contractor, the two firms (Hughes and North American) began to design the necessary equipment, and almost immediately ran into some problems with the proposed radar.
