The North American XF-108 Rapier occupies a spot in aviation history as yet another one of the many ambitious, yet unrealized, dreams of the 1950s. It was to be an interceptor with Mach 3 capabilities to answer the looming threat of Soviet bombers, one which would have completely changed the face of aerial combat with advanced technology and previously unmatched speed.
In the 1950s, the U.S. A bomber blitz from the Soviets was the fearful reason that led the Air Force to take a succession of ambitious interceptor projects. One of the most interesting was the XF-108 Rapier. North American Aviation received the development contract in 1957 for this two-man interceptor, whose performance design called for Mach 3, a thousand-mile range, and an altitude of seventy thousand feet. This was a time when the subsonic F-86 Sabres and MiG-15s were just starting to engage in dogfights over Korea.
Most of the features were carried over from its larger cousin, the XB-70 Valkyrie strategic bomber, which would have shared the General Electric YJ93 engines and a similar crew escape capsule. The Rapier, according to the writers Dennis Jenkins and Tony Landis, would be used as a “gap-filler for the Distant Early Warning (DEW) radars,” With interceptors stationed at remote Arctic airfields, holes in the radar coverage could be filled in, monitoring an area bigger than Texas every hour.
The most radical feature of the XF-108 was its internal rotary missile launcher feature unique in any American fighter. It would have carried three long-range GAR-9 missiles, designed to fit into the slim stores bay between the aircraft’s huge engines and intakes. As the weapons bay door opened, it rotated to expose the missiles, thereby eliminating the need for doors projecting into the airstream.
Its primary mission would be to intercept and destroy Soviet bombers laden with nuclear weapons before they could pose any sort of threat to American territory. The Rapier was designed for this mission with a Hughes AN/ASG-18 radar first for a U.S. pulse-doppler able to lock onto individual targets while scanning the general area. This radar, coupled with GAR-9 missiles, would permit the XF-108 to fire at targets well over 100 miles away.
Despite its promising design, however, the XF-108 faced insurmountable challenges. President Eisenhower resisted a price tag of $4 billion for 480 F-108s figure equated to $33 billion in today’s dollars. More critically, the advent of intercontinental ballistic missiles began to overshadow the threat posed by manned bombers. By the late 1950s, the focus of military budgets shifted away from air defense, leading to the cancellation of the XF-108 in September 1959.
While the XF-108 never reached operational status, its technological dividends were not lost. The features of the aircraft were passed to the North American A-5 Vigilante, a bomber that would see extensive service in the Vietnam War. The GAR-9 missile evolved into the AIM-47, which would eventually help influence the design of the AIM-54 Phoenix missile that equipped the F-14 Tomcat.
The XF-108 represented a quantum leap in aviation technology, but the changing nature of military threats placed real limits on the utility of the design. If the aircraft had entered service, the United States would have operated a fleet of very fast but unmaneuverable fighters better suited to countering a Soviet bomber threat than engaging in the tactical air combat that characterized the Vietnam War.
The XF-108 Rapier has to rank as one of the most intriguing “what-ifs” that ever took or, in this case, never took to the air, a function both of technological ambitions typical of the era and shifting priorities that finally laid the craft to rest.