XF-103 | The Mach 3 Interceptor

The Republic XF-103 was an American project to develop a powerful missile-armed interceptor aircraft capable of destroying Soviet bombers while flying at speeds as high as Mach 3. Despite a prolonged development, it never progressed past the mockup stage

Development

In 1949, the USAF issued a request for an advanced supersonic interceptor to equip the Air Defense Command . Known formally as Weapon System WS-201A, but better known informally as the 1954 Interceptor it called for a supersonic aircraft with all-weather capability, powerful airborne interception radar and air to air missile armament. Republic was one of six companies to submit proposals. On 2 July 1951, three of the designs were selected for further development, Convair's scaled-up XF-92 that evolved into the F-102, a Lockheed design that led to the F-104 and Republic's AP-57. AP-57 was an advanced concept to be built almost entirely of titanium and capable of Mach 3 at altitudes of at least 60,000 feet (18 km).

A full-scale mock-up of the AP-57 was built and inspected in March 1953. A contract for three prototypes followed in June 1954. Work on the prototypes was delayed by continued problems with the titanium construction, and more by continuing problems with the proposed Wright 167 engine. The contract was later reduced to a single prototype.

Design and Characteristics 

The engine used were Wright J67 turbojet engine supplimented by an RJ-55-W-1 ramjet behind it Connecting the two were a series of movable ducts that could route air between the engines. At low speeds the aircraft would be powered by the J67, with the RJ55 acting as a traditional afterburner, producing a total of about180 kN thrust. At high speeds, starting above Mach 2.2 the jet engine would be shut down and the airflow from the intake would be routed around the jet engine and directly into the RJ55. Although the net thrust was reduced by shutting down the jet, operating on the ramjet alone allowed the aircraft to reach much higher speeds.

All of the control surfaces were pure delta wings , the wing was tilted upwards to increase the angle of incidence while keeping the fuselage nearly horizontal , The system also allowed the fuselage to fly flat to the airflow at various speeds, setting the trim angle independent of the aircraft as a whole. This decreased trim drag, thus improving range.

The entire nose of the aircraft was taken up by the large Hughes radar set, which (at the time) offered long detection ranges. Guidance and fire control were to be provided by the same MX-1179 package being developed for all of the WS-201 designs. Hughes had won this contract with their Hughes MA-1 fire control system, which was under development.

Weapons were carried in bays located on the sides of the fuselage behind the cockpit, which opened by flipping upward, thereby rotating the missiles out of their bays. It was to be armed with six GAR-1/GAR-3 Falcon(then known as MX-904), with a likely arrangement of three or four each GAR-1s and GAR-3s

 Nothing ever came of the proposal, and testing of the ASG-18/GAR-9 was carried out on a modified Convair B-58 hustler instead